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MODEL PAPER-1
CLASS-XI(2016-17)
SUB-CHEMISTRY
TOTALMARKS-70
General Instructions :
1.
All questions are compulsory
2.
Q1 to Q5 are very short questions each carry 1 mark.
3.
Q6 to Q10 are short questions each carry 2 marks.
4.
Q11 to Q22 short answer questions and carry 3 marks.
5.
Q23 is value based questions and carry 4 marks.
6.
Q24 to Q26 are long questions and carry 5 marks.
7.
Use log tables if necessary and calculators are not allowed
1. What do you mean by a limiting reagent?
1M
+
22. Write the electronic configuration of the following ions: a) Na b) O
1M
3. What would be the IUPAC name and symbol for the element with atomic number117?
1M
4. State Le-chatelier’s principle.
1M
5. Name the method of separation used to purify liquids having very high boiling point
(which decompose at or below their boiling point).
1M
6. Calculate the number of atoms in i) 52u of He gas ii) 13 moles of He.
2M
7. Express the following in the scientific notation: i) 0.0048 ii) 500.0 iii) 6.0012
iv) 8008
2M
8. a)
Why is Li2CO3 decomposed at a lower temperature whereas Sodium carbonate at
higher temperature?
b)
Why are Potassium and Cesium, rather than Lithium used in photoelectric cells?
2M
9. Distinguish between a sigma and a pi bond.
2M
10. Explain why is there a phenomenal decrease in ionization enthalpy from carbon to
silicon?
2M
11. a)
In terms of period and group where would you locate the element with atomic
number 114?
b)
Predict the formulae of the stable binary compounds that would be formed by the
combination of the following pairs of elements.
i)
Lithium and oxygen ii) magnesium and nitrogen iii) Silicon and oxygen
iv)
Phosphorus and fluorine
3M
12. a)
What is meant by the term bond order?
b)
What is the total number of sigma and pi bonds in the following molecules?
i)
C2H2
ii)
C2H4
3M
0
13. Calculate the volume occupied by 5.0 g of acetylene gas at 50 C and 740 mm pressure.
3M
14. a)
What do you mean by enthalpy of a reaction?
b)
Enthalpies of formation of CO (g), CO2 (g), N2O (g) and N2O4(g) are -110, -393,
81 and 9.7 KJ/mol respectively. Find the value of ∆rH for the reaction:
N2O4 (g) + 3CO (g)  N2O (g) + 3CO2(g)
3M
15. a)
State Hess’s law of constant heat summation.
b)
In a process, 701 J of heat is absorbed by a system and 394 J of work is done by
the system. What is the change in internal energy for the process?
c)
For the reaction, 2Cl (g)  Cl2 (g), what are the signs of ∆H and ∆S?
3M
16. a)
Assign oxidation number to the underlined elements in each of the following
species: i)
NaH2PO4 ii) H2S2O7
b)
Write formulae for the following compounds:
i)
Mercury (II) chloride ii)
Chromium (III) oxide
c)
Identify the substance oxidized, reduced, oxidizing agent and reducing agent for
the given reaction: N2H4 (l) + 2H2O2 (l)  N2 (g) + 4H2O (l)
3M
17. Complete the following chemical reactions.
3M
i)
PbS (s) + H2O2 (aq) 
ii)
MnO4- (aq) + H2O2 (aq) 
iii)
Ca3N2 (s) + H2O (l) 
18. a)
Find out the oxidation state of sodium in Na2O2.
b)
Explain why is sodium less reactive than potassium?
3M
19. What happens when
a) Borax is heated strongly
b) Boric acid is added to water
c) Aluminium is treated with dilute NaOH.
3M
20. a)
What is an electrophile? Give example.
b)
Why is it necessary to use acetic acid and not sulphuric acid for acidification of
sodium extract for testing sulphur by lead acetate test?
3M
21. a)
What is metamerism? Give example.
b)
In the estimation of sulphur by carius method, 0.468 g of an organic sulphur
compound afforded 0.668 g of barium sulphate. Find the percentage of sulphur in the
given compound.
3M
22. a)
Draw cis and trans isomers of the following compounds and also write their
IUPAC names.
i)
CHCl=CHCl ii) CH3CH=CHCH3
b)
Why does Benzene undergo electrophilic substitution reactions easily and
nucleophilic substitutions with difficulty?
3M
23. Water is a universal solvent. But alcohol also dissolves most of the substances soluble in
water. And also many more. Boiling point of water is 100oC and that of alcohol is 80oC.
The specific heat of water is much higher than the specific heat of alcohol.
a) List out three possible differences if instead of water as the liquid in our body we had
alcohol.
b) What value can you derive from this special property of water and its innumerable
uses in sustaining life on earth?
4M
24. a)
State Pauli’s exclusion principle.
b)
Name four quantum numbers and what are their significance.
5M
OR
a) State Heisenberg Uncertainty principle.
b) What is the energy in joules, required to shift the electron of the hydrogen atom from
the first Bohr orbit to the fifth Bohr orbit, and what is the wavelength of the light
emitted when the electron returns to the \ground state? The ground state electron
energy is -2.18x10-11 ergs.
c) Assign the values of n, l and m for a (i) 2s orbital (ii) 4d orbital
5M
25. At 473 K, equilibrium constant, Kc for the decomposition of phosphorus pentachloride,
PCl5 is 8.3 x 10-3. If the decomposition is depicted as
PCl5 (g)
PCl3 (g) + Cl2 (g) ∆rH0 = 124.0 kJ mol-1
a) Write an expression for Kc for the reaction.
b) What is the value of Kc for the reverse reaction at the same temperature?
c) What would be the effect on Kc if (i) more PCl5 is added (ii) the pressure is
increased and (iii) the temperature is increased?
5M
OR
a) What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the
following species: HNO2, CO32-, S2- and OHb) The pH of a sample of vinegar is 3.76. Calculate the concentration of hydrogen ion in
it.
c) Which of the following are Lewis acids? H2O, BF3, H+, NH4+
5M
26. a)
Write the IUPAC name of (CH3)3CCH2C(CH3)3
b)
Alkane ‘A’ contains three C-C, eight C-H ϭ bonds and one C-C π bond. ‘A’ on
ozonolysis gives two moles of an aldehyde of molar mass 44 amu. Write IUPAC name
of ‘A’.
c)
How will you convert benzene into acetophenone?
d)
State Markovnikov’s rule.
e)
What are the necessary conditions for any system to be aromatic?
5M
OR
a) Write the structure of 2,4-dimethylhex-2-ene.
b) Write the chemical equation for Wurtz reaction.
c) Name the compound formed by the ozonolysis of 2-methylpropene.
d) Arrange the following set of compounds in order of their decreasing relative
reactivity with an electrophile , E+
(i) Chlorobenzene, 2,4-dinitrochlorobenzene, p-nitrochlorobenzene
(ii) Toluene, p-H3C-C6H4-NO2, p- NO2-C6H4-NO2
e) Explain the acidic nature of acetylene.
5M
ANSWER KEY
1. The reactant which gets consumed and limits the amount of product formed is called the
limiting reagent.
1M
2. a)
1s22s22p6
b)
1s22s22p6
½+1/2 = 1M
3. Ununseptium, Uus.
1M
4. A change in any of the factors that determine the equilibrium conditions of a system will
cause the system to change in such a manner so as to reduce or to counteract the effect of
the change.
1M
5. Distillation under reduced pressure.
1M
6. i)
52u of He = 52u/4u =13 atoms (1molecule of He=4u, 4u=1 He atom)
ii)
1 mole of He has 6.022x1023atoms, so 13 moles of He has
13x6.022x1023 = 7.83x1024 atoms.
1+1=2M
-3
2
3
7. i) 4.8x10 ii) 5.000x10 iii) 6.0012 iv) 8.008x10
1/2x4=2M
8. a)
Lithium ion is small in size, whereas carbonate ion is a large anion. A substance
containing a small cation and large anion are less stable.
b)
The ionization energies of Potassium and Cesium are much lower than that of
Lithium.
1+1=2M
9. Any two differences.
2M
Sigma (ϭ) bond
Pi (π) bond
It is formed due to axial overlap of the two
orbitals.
This bond is formed by the lateral overlap
of two p-orbitals.
The bonding is relatively strong.
The bonding is weak.
There can be only one sigma bond between
atoms.
There can be more than on pi bond
between the two atoms.
It can be formed independently.
It can be formed only after sigma bond has
been formed.
10. A sharp decrease in the ionization enthalpy in going from carbon to silicon can be
attributed to the combined effect of the
i)
increase in the atomic size
ii)
more effective shielding of the outer electrons by the inner core of electrons. 2M
11. a)
The element with atomic number 114 is expected to lie in the seventh period and
group 14.
1M
b)
i) Li2O ii) Mg3N2 iii) SiO2 iv) PF5
1/2x4=2M
12. a)
Bond order is defined as one half the difference between the number of electrons
present in the bonding and the antibonding orbitals.
b)
i) In C2H2, sigma bonds=3, pi bonds = 2,
ii) C2H4, sigma bonds = 5, pi bonds = 1
1+1+1= 3M
13. Molar mass of acetylene (C2H2) M = (2x12+2x1) = 26g/mol
Mass of acetylene , m = 5.0 g
Temperature, T = 500C + 273 = 323 K
Pressure, P = 740 mm Hg = 740/760 = 0.9737 atm.
Using the gas equation, PV = nRT
V=nRT/P =mRT/MP = 5x 0.082x323/26x0.9737 = 5.23 L
3M
14. a)
The amount of heat absorbed or evolved when stoichiometric amounts of the
reactants as represented by the balanced chemical equation have completely reacted
under constant pressure conditions is termed as the enthalpy of reaction.
1M
b)
∆rH = ∑ ∆fH(products) - ∑ ∆fH(reactants)
= [81kJ mol-1 + 3 x (-393 kJ mol-1)] - [9.7kJmol-1 + 3 x (-110 kJ mol-1)]
= (-1098) – (-320.3) = -777.7 kJ mol-1
2M
15. a)
Hess’s law of constant heat summation states that “The enthalpy change during a
chemical reaction is independent of the manner in which the change is brought about”
b)
Heat absorbed by the system, q = + 701 J
Work done by the system w = -394 J
Change in the internal energy, ∆U = +701 – 394 = + 307 J.
c)
For the given reaction, ∆H is negative and ∆S is negative.
1+1+1=3M
16. a) i) oxidation number is +5, ii) oxidation number is +6
b) i) HgCl2 ii)
Cr2O3
c) oxidized -N2H4, reduced - H2O2 ,oxidizing agent -H2O2 ,reducing agent - N2H4.3M
17. i)
PbS (s) + 4H2O2 (aq) 4 H2O + PbSO4
6H+
ii)
2MnO4- (aq) + 5H2O2 (aq) 2Mn2+ (aq) + 8H2O + 5O2 (g)
iii)
Ca3N2 (s) + 6H2O (l)  3Ca(OH)2 + 2NH3
1+1+1=3M
18. a)
The oxidation state of sodium in Na2O2 is +1.
b)
Sodium and potassium both are electropositive elements. The ionization enthalpy
of potassium is lesser than that of sodium. That is why potassium is more reactive than
sodium. So, sodium is less reactive than potassium.
1+2=3M
19. a)
When Borax is heated strongly, it loses water of crystallization and forms
colourless, transparent glass-like bead which is made up of sodium metaborate and boric
anhydride.
∆
∆
Na2B4O7.10H2O Na2B4O7 2NaBO2 + B2O3
b)
When Boric acid is added to water, it accepts a hydroxyl ion and behaves as a
Lewis acid.
B(OH)3 + H2O  [B(OH)4]- + H+
c)
When aluminium is treated with NaOH, it forms aluminates and hydrogen gas is
liberated.
2Al + 2NaOH + 2H2O  2NaAlO2 + 3H2 (g)
1+1+1=3M
20. a)
A reagent that takes away an electron pair is called an electrophile (E+) i.e.,
electron seeking and the reaction is called electrophilic.
Example: carbocations and neutral molecules having functional groups like carbonyl
group or alkyl halides.
b)
This is because if sulphuric acid is used, it will decompose sodium sulphide
(Na2S) formed during fusion. As a result, the solution will give a negative test for the
presence of sulphur in the sample.
1½ +1½=3M
21. a)
It arises due to different alkyl chains on either side of the functional group in the
molecule.
Example: C4H10O represents methoxypropane (CH3OC3H7) and ethoxyethane
(C2H5OC2H5).
b)
Percentage of sulphur in the compound = mass of BaSO4x32x100/233xmass of
the compound.
= 0.668x32x100/233x0.468 = 19.6%
Percentage of sulphur in the compound = 19.6%
1+2=3M
22. a)
i)
ii)
b)
Due to the presence of 6π electrons, benzene behaves as a rich source of electrons,
thus being easily attacked by reagents deficient in electrons.
2+1=3M
23. a). i) Even a small raise in temperature in the surroundings will raise the temperature of
the body because the specific heat of alcohol is much less than the specific heat of water.
In order to cool the body more sweating will take place.
ii)
As there is less H bonding in alcohol it will get evaporated faster. The alcohol
will be evaporated at such a fast rate that the liquid has to be ingested always.
iii)
Ice which floats on water helps aquatic life to exist even in winter as water
insulates the heat from liquid below it to go back to the surroundings. Solid
alcohol does not have such special properties.
b. Praise is to the almighty that has so thoughtfully given such special properties to water
and made it a liquid that could sustain life.
4M
24.a) “No two electrons in an atom can have same values for all the four quantum
numbers.”
1M
b) The four quantum numbers are
i) Principal quantum number
ii) Azimuthal quantum number
iii) Magnetic quantum number
iv) Spin quantum number
Principal quantum number (n): It determines the main energy level, called shell in
which the electron is present. It specifies the location and energy of an electron in
any atom. It is a measure of the effective radius of the electron cloud sphere.
Azimuthal quantum number (l): It describes the shape of the subshell in which the
electron resides. It can have only positive integral values from 0 to (n-1). It gives
the values of the orbital angular momentum of the electron in terms of h/2π units.
Magnetic quantum number (m): It determines the orientation of the orbitals in space.
It can have integral values from –l to +l through 0. Two orbitals in the same shell
can have identical n and l values, but they must have different values of m.
Spin quantum number (s): The electron in an atom revolves around the nucleus, and
also spins about its own axis. This rotation of electron about its own axis is
described by spin quantum number. It can have only two values for an electron,
+½ and -½.
4M
OR
a)
It states that it is impossible to determine simultaneously, the exact position and exact
momentum (or velocity) of an electron.
1M
-11
2
b)
Energy of electron in nth orbit of H atom is given by -2.18 x 10 erg/n
Then E1 = -2.18 x 10-11erg = -218 x 10-13erg, E5 = -2.18 x 10-11erg/52= -8.72 x 10-13erg
Energy required for the electronic transition, ∆E = E5 - E1 = -8.72 x 10-13erg – ( -218 x
10-13erg) = -2.09 x 10-11erg
Wavelength of the emitted radiation, λ=ch/∆E = 3x 1010 x 6.626 x 10-27/-2.09 x 10-11erg
λ = 9.511 x 10-6 cm.
3M
c)
(i) n =2, l =0, m =0 (ii) n =4, l = 2, m= -2,-1,0,+1, +2
1M
25.a)
b)
Kc = [PCl3] [Cl2]/[PCl5]
Kc (reverse reaction) = 1/Kc(forward reaction) = 1/8.3x10-3 = 120.5
c) i) When more PCl5 is added to the reaction mixture, the concentrations of PCl3 and Cl2
will increase in such a way that the value of Kc remains unchanged.
ii) when pressure is increased, the reaction will move in a direction of lower volume i.e.,
backwards. As a result, the value of Kc will decrease.
iii) the reaction is endothermic in nature. So, increase in temperature will favour the
forward reaction. As a result, the value of Kc will increase.
5M
OR
a)
A pair of an acid and a base which differ from one another by a proton are said to be a
conjugate acid-base pair.
The conjugate acid/base for HNO2, CO32-, S2- and OH- are NO2-, HCO3-, HS- and H2O
b)
Given: pH = 3.76, - log [H+] = 3.76, [H+] = Antilog (-3.76) = 1.7 x 10-4
c)
BF3, H+ are Lewis acids.
2+2+1=5M
26. a)
2,2,4,4-tetramethylpentane.
b)
But-2-ene
c)
Benzene can be converted into acetophenone by the reaction of benzene with acetyl
chloride.
Markovnikov’s rule states that the negative part of the addendum gets attached to that
carbon atom which possesses lesser number of hydrogen atoms.
e)
Planar, conjugated ring system with delocalization of (4n+2) π electrons, where, n is
an integer.
1+1+1+1+1=5M
d)
OR
a.
ab)
c) Propan-2-one
d)
i)
Chlorobenzene> p-nitrochlorobenzene>2,4-dinitrochlorobenzene
ii)
Toluene > p-H3C-C6H4-NO2>p- NO2-C6H4-NO2
e) In acetylene, carbon atoms are sp hybridized. The sp orbital has more s-character as
compared to sp2 and sp3 orbitals. The sp hybridized carbon is more electronegative than sp2 and
sp3hybridised carbon atoms. Due to this, the hydrogen atoms of acetylenic carbon develop a
more positive charge and is acidic in character.
1+1+1+1+1=5M
MODEL PAPER-2
CLASS-XI(2016-17)
SUB-CHEMISTRY
TOTALMARKS-70
General Instructions :
1.
All questions are compulsory
2.
Q1 to Q5 are very short questions each carry 1 mark.
3.
Q6 to Q10 are short questions each carry 2 marks.
4.
Q11 to Q22 short answer questions and carry 3 marks.
5.
Q23 is value based questions and carry 4 marks.
6.
Q24 to Q26 are long questions and carry 5 marks.
7.
Use log tables if necessary and calculators are not allowed
1. Which of the following are isoelectronic species?
1M
Na+, K, Ca2+, S22. What would be the IUPAC name and Symbol of an element with atomic no. 118
1M
3. Write the conjugate bases for the following Bronsted acids H2SO4,
HCO3.
1M
4. Assign the oxidation no. to the underlined element in each of the following
speciesH2S2O7, NaBH4.
1M
5. What do you mean by demineralized water?
1M
6. a)Using s,p,d,f notations, describe the orbital with following quantum numbers:
i) n=3, l=1
ii) n=2, l=0
b) State Heisenberg’s Uncertainty principle.
7. At equilibrium the concentration of N2 = 3.0 x 10
2M
-3
M, O2 = 4.2 x 10-3M and
NO= 2.8 x 10-3in a sealed Vessel at 800 K. What will be the KC for the reaction?
2M
8. How many significant figures are present in the following:
i) 0.0025
ii) 5005
iii) 126,000 iv) 2.0034
2M
9. Write the Resonance structures for SO3, NO3 .
OR
Indicate the magnetic properties of the following species
O2, O2+, O2- (superoxide), O22(Peroxide)
2M
10. A balloon is filled with Dihydrogen gas at room temperature. It will burst, if
pressure exceeds 0.2bar. If at 1 bar pressure the gas occupies 2.27L volume, up to
what volume can the balloon be expanded?
2M
11. A compound contains 4.07% hydrogen, 24.27 % carbon and 71.65% chlorine. Its
molar mass is 98.96g. What are its empirical formula and molecular formula?
3M
12. a) State photoelectric effect.
b) What are the frequency and wavelength of a photon emitted
during a transition from n=5 state to the n=2 state in the
hydrogen atom?
3M
13. a) Explain Why cations are smaller than anions in radii than parent atoms?
b) Which of the following species will have the largest and the smallest
size? Give reason
Mg, Mg2+, Al, Al3+
3M
14. a) Draw the shape of the following molecules based on VSEPR theory
CH4, SF6
b) Which out of NH3 and NF3 has higher dipole moment and why? 3M
15. a) Under what conditions, real gases show ideal gas behavior?
On a ship sailing in Pacific Ocean where temperature is 26.40C, a balloon is
filled with 1.4L air. What will be the volume of the balloon when the ship
reaches Indian Ocean, where the temperature is 29.70C.
3M
16. a) The value of Kc for the reaction
2A
B + C is 2 x 10-3. At a given time, the composition of reaction
mixture is [A] = [B] = [C]= 3 x 10-4. In which direction the reaction will proceed?
b) Classify the following species into Lewis acids and Lewis bases.
HO-, BCl3
a) State Le Chatelier’s principle.
b) For the reaction N2 (g) + 3H2 (g
2NH3 (g) + heat.
i) What will be the effect of increasing temperature on the yield of NH 3?
ii) What is the effect of adding N2 (g) and H2 (g) on the yield of NH33M
17. Permanganate (VII) ion, MnO4- in basic solution oxidises iodide ion I to
produce molecular Iodine (I2) and manganese oxide (MnO2). Write a
balanced ionic equation to represent this redox reaction.
3M
18. a) What causes the permanent hardness of water? Mention one method
to remove permanent hardness.
b) Complete the following equation:
2Fe2+ (aq) + 2 H+ (aq) + H2O2 (aq)
c) State the basic principle of Hydrogen economy
3M
19. a) The Eθ for Cl2/ Cl-is+1.36, for I2/ I-is 0.53, Na +/ Na is - 2.71
and for Li+/Liis-3.04. Arrange the following ionic species
indecreasing order of reducing strength.
I-,Cl-, Li, Na
b) KO2 is paramagnetic in nature. Give reason.
c) During baking of bread baking powder is added to dough. Write the balanced
chemical equation involved in it.
OR
a) What do you mean by diagonal relationship?
b) Be and Li shows diagonal relationship. Mention any two similarities between
them.
3M
20. a) How many sigma and pie bonds are present in the following molecule.
CH≡C CH═CHCH3
b) Write the structural formula for 6-methyloctan-3-ol.
c) Using curved arrow notation, show the formation of reactive intermediates
when the following covalent bonds undergo heterolytic cleavage:
a) CH3-CN
b) CH3-Cu
3M
21. a) In which C-C bond of CH3CH2CH2Br, the inductive effect is expected to
be the least?
b) Write the resonance structures of CH2=CH-CHO..
c) Explain why (CH3)3C+ is more stable than CH3 +CH2 and +CH3 is the
least stabled cation.
3M
22. Preeti’s maid servant Mrs. Sheela uses Chulha at her home and burns
Fire wood, dry leaves etc. every day. Lot of pollution is created all
around. She has lot of respiratory problems and her children also do
not remain well. On the other hand, Preeti’s car driver Mr. James has
LPG gas at home which does not create pollution. Hence he himself
and his children are healthy .
a) What values are possessed by Mr. James?
b) Why are Mrs. Sheela’s children suffering from Respiratory problems?
c) Write the main constituents of LPG gas
4M
23. a) Express the change in internal energy of a system when no work done
on the system, but q amount of heat is taken out from the system and
given to the surroundings. What type of wall does the system have?
b) State Hess Law of Constant heat summation
c) Write the conditions in terms of ∆H and ∆S when a reaction would be
always spontaneous.
d) For the reaction at 298K: 2A + B
C; ∆H= 400 kjmol-1 and
∆S = 0.2kj mol-1K-1. At what temperature will the reaction spontaneous
considering ∆H and ∆S to be constant over the temperature range?
OR
a) What do understand by enthalpy of formation?
b) Will entropy increase or decrease in the following?
2NaHCO3 (s)
Na2CO3 (s) + CO2 (g) + H2O (g)
c) Calculate lattice enthalpy of Na+Cl- (s) for the given reaction with the
help of Born-Haber cycle.
Na+Cl- (s)
Na+ (g) + Cl- (g)
∆latticeHθ
= +788 kj mol-1
∆subHθ= 108.4kj/mol
∆f Hθ=496kj/mol
∆bondHθ for cl-cl= 242kj/mol
5M
24. a) Boron is unable to form BF6, why?
b) Suggest a reason as to why CO is poisonous.
c) Conc.HNO3 can be transported in aluminium container. Why?
d) What happens when boric acid is heated strongly?
e) What happens when CO is heated with ZnO?
OR
a) Boric acid is considered as weak acid. Give reason.
b) Select the members of the group 14 that (i) form the most acidic oxide
ii) is commonly found in +2 oxidation state.
c) Diamond is covalent, yet it has high melting point. Why?
d) White fumes appear around the bottle of anhydrous aluminium chloride.
Give reason
e) How is synthetic gas produced commercially?
5M
25. a) Write the structural formula of Nitro aniline
b) Classify the following into electrophile/ nucleophile
HS-, BF3, C2H5O-, (CH3)3N:
c) On complete combustion of 0.246g of an organic compound gave
0.198g of Carbon di oxide and 0.141g of water. Determine the
percentage composition of carbon and hydrogen in the compound.
OR
a) Write the IUPAC name of (CH)3CCH2C(CH)3.
b) Draw cis and trans isomers of C2H5CCH3 = CCH3C2H5
c) Write the major product and minor product formed in the given
reaction and give reason for the major product formed.
CH3-CH=CH2 + H-Br
d) Write the products formed during ozonolysis of propene.
e) Ethyne is more acidic in nature than ethane. Why?
SCORING KEY FOR MODEL SESSION ENDING EXAMIANTION-2016
5M
Q.No
Value Point
Marks
1
Ca2+, S2-
½+½
2
Ununoctinum, Uuo
½+½
3
HSO4-, CO32-
½+½
4
S is 6, B is 3
½+½
5
The Water which is free from all soluble mineral salts, is called
demineralized water.
1
a) i) 3p ii) 2s
6
½+½
b) Principle
Formula
½
Substitution
½
Calculation of Kc value
1
7
Answer Kc= 0.622
8
i) 2 ii 4 iii) 3 iv) 5
Each correct structure
4 x ½ =2
1 +1
OR
9
O2 is paramagnetic
O2+ is paramagnetic,
O2- is paramagnetic ,
4 x ½ =2
O22- is diamagnetic
Formula
½
Substitution
½
Calculation of V2 value
1
10
Answer V2= 11.35L
2
Sequence of steps
½
11
Empirical formula = CH2Cl
½
Molecular formula= C2H4Cl2
12
Photoelectric effect
1
Formula
½
Substitution
½
Calculation .
1
Answer √= 6.91 x 1014 Hz ʎ = 434nm
13
a)Correct reason
1
b)Largest size: Mg , Smallest Size: Al3+
1
Reason
1
a) CH4= tetrahedral
14
SF6= Octahedral
b) NH3
Reason
½+½
1
1
a) Low pressure, High temperature
b)Formula
½+½
Substitution
½
Calculation of V2 value
½
15
Answer V2= 1.575L
1
a)Calculation of Qc
1
16
As Qc> Kc , the reaction proceeds in reverse direction
1
b) HO- Lewis Base while BCl3 is a Lewis acid
a) LeChatelier principle
1
b) Yield decreases as increase in temperature favours endothermic
17
reaction
1
Yield increases as increase in concentration favours ammonia
1
formation
18
Redox equation with all necessary steps
6 x ½ =3M
a) Salts of Ca, Mg contain bicarbonates, sulphates, chlorides
present in water makes water hard.
19
½
Treatment with NaHCO3 ( Or) Calgon method
½
b) 2Fe3+ + 2H2O (aq)
½+½
c) Transportation and storage of energy in the form of liquid or
gaseous Dihydrogen
1
a) Correct order
1
b) One unpaired e- in π*2p molecular orbital
1
c) Correct equation
1
20
OR
a) Definition of diagonal relationship
1
b) Any two similarities between Be & Li
1+1
a)
21
bonds: 10, π bonds: 3
½+½
b) Correct structural formula
1
c) Proper notation
½+½
a) Between carbon-3 and H
1
b) Resonating structure
1
22
c) Due to hyperconjugation as ( CH3)3 C+ has 9 C-H bonds, in +CH3 1
vacant p-orbital is perpendicular to the plane in which C-H bond
lie. Hence can’t overlap with it. So least stable
23
a) Any two valid values shown by Mr. James
½+½
b) may be due to CO and oxides of Sulphur
1
c) Mainly n-butane & isobutane
½+½
a) ∆ u=-q, thermally conducting walls
b) Hess law of constant heat of summation
1
c) ∆H is negative or exothermic ∆s +ve or entropy increases
1
d) For spontaneous reaction ∆G is negative
1
Calculation Final Answer = T> 2000K
2
24
OR
a) Meaning of enthalpy of formation
b) Entropy Increases
1
c) Born-Haber cycle representation for the calculation of lattice
1
enthalpy
Answer= 788kj
a) Due to non-availability of vacant d orbital
1
b) Competes with O2 for hemoglobin and is bonded to hemoglobin
1
so that O2 is not carried to cells
25
3
1
c) Passive layer of Al2O3 acts as a protective layer
1
d) Forms HBO2 and then B2O3
1
e) Co2 + Zn is formed
OR
a) Not able to release H+ ions on its own
1
b) i) C
1
ii) Pb
c) 3 dimensional network involves strong C-C bonds, difficult to
break
1
1
d) Anhydrous AlCl3 hydrolyses partially with atmospheric moisture
1
to liberate HCl gas and moist HCl appear white
e) Passing steam over red hot coke with equation
a) Correct structural formula
b) Electrophile : BF3
½
Nucleophile : (CH3)N, HS-, C2H5O- 3x ½
c) Formula, Substitution, Calculation
% of Carbon is 21.95%, % of H is: 4.5 % (1+1)
1
2
2
OR
a) 2,2,4,4, tetra methyl pentane
26
b) Cis bond structure ½ M
1
transbond structure ½ M
1
c) Major product is CH3-CH2-CH2Br
Minor product is CH3-CHBr-CH3
Markovnikov rule
d) Ethanal , Methanal ½ + ½ Mark
e) proper reason
1
1
1
MODEL PAPER-3
CLASS-XI(2016-17)
SUB-CHEMISTRY
TOTALMARKS-70
General Instructions :
1.
All questions are compulsory
2.
Q1 to Q5 are very short questions each carry 1 mark.
3.
Q6 to Q10 are short questions each carry 2 marks.
4.
Q11 to Q22 short answer questions and carry 3 marks.
5.
Q23 is value based questions and carry 4 marks.
6.
Q24 to Q26 are long questions and carry 5 marks.
7.
Use log tables if necessary and calculators are not allowed
Q 1. Arrange the following in increasing order of their ionic radii ?
N³⁻ , O²⁻ , F⁻ , Na⁺ , Mg²⁺ , Al³⁺
1M
Q 2. How will you convert the following compound into benzene.
(a)Ethyne
1M
Q 3 How will you convert the following compound into benzene.
(a) Hexane
1M
Q4 . Complete the following reaction.
CO(g) + H₂(g)
Δ
Catalyst
1M
Q 5. What is Eutrophication ?
1M
Q 6 . The density of 3M solution of NaCl is 1.25 g L⁻¹. Calculate the molality of solution? 2M
Q 7 Although both CO₂ and H₂O are triatomic molecules the shape of H₂O molecule is bent
while that of CO₂ is linear. Explain this on the basis of dipole moment?
2M
Q 8 . What do you understand by the term auto protolysis of water? What is it's significance?2M
Q 9.What do you mean by the green chemistry ? How will it help decrease environmental
pollution ?
2M
Q 10 Give the IUPAC names of the following compounds .
(a) CH₃ - CH₂ – CH – CH = CH - CH₂ - CHO
|
CH3
(b) CH₃ - CH₂ - CH - CH₂ - CH - CH₃
|
|
CH₂OH
CH₂-CH₃
2M
Q11. a) Calculate the mass of Sodium which contains same numbers of atoms as are present in
4 g of Calcium. Atomic masses of Sodium and Calcium are 23 and 40 respectively ?
b) How many significant figures are present in 0.0025 ?
3M
Q 12.a) Calculate he wave number for the longest wavelength transition in the Balmer series of
atomic Hydrogen ?
b) How many electrons in an atom may have the following quantum numbers ?
n=4 , m= -½
3M
Q 13. Which type of hybridization found in PCl₅. Explain why are the axial bonds are longer
than equatorial bonds?
b) Predict the shapes of following molecules using VSEPER model ?
(a)BeCl₂
(b) SiCl₄
3M
Q 14.a) Identify the substance oxidized, reduced, oxidizing agent, reducing agent for following
reaction.
HCHO(l)+ 2[Ag(NH3)2] (aq) +3OH⁻(aq)2Ag (s)+ HCOO⁻(aq) + 4NH₃(aq)+ 2H2O (l)
b) Assign the oxidation number to underlined element .
KMnO4
3M
Q 15 The uncertainty in the position and the velocity of a particle are 10⁻² m and 5.27 x 10⁻²⁴
ms⁻¹ respectively. Calculate masses of the particles.( h= 6.626 x 10⁻³⁴ Kg m²s⁻¹ ) ?
3M
Q 16 Account for the following.
1.Firstionisation enthalpy of N is more than O.
2.Ionic size of Cl- is greater than K+ though two ions are isoelectronic.
3.Electron gain enthalpy of noble gasses are positive .
3M
Q 17. Compare the relative stability of the following species and indicate their magnetic
properties.
O₂, O₂⁺, O₂⁻
3M
Q 18. For a reaction : 2A(g) + B(g)
2D(g)
Calculate ΔG298өFor the reaction and predict whether the reaction is spontaneous or not ? 3M
Q 19. Predict in which of the following, entropy increases or decreases.
1. A liquid crystallises into solid .
2. Temperature of crystalline solid is raised from 0 K to 115 K.
3. 2NaHCO₃
Na₂CO₃ + CO₂ + H₂
3M
Q 20.The ionisation constant of HF, HCOOH and HCN at 298K are 6.8 x 10⁻⁴, 1.8 x 10⁻⁴
respectively. Calculate the ionisation constant of corresponding conjugate base ?
3M
Q 21.a) The species H₂O, HCO₃⁻, HSO₄⁻, can act both as bronsted acids and bases. For each
case give the corresponding conjugate acid and base ?
.
b) Falling liquid drops are spherical why ?
3M
Q 22. Arrange benzene, n-hexane and ethyne in decreasing order of acidic behaviour. Also give
reason for this behaviour ?
3M
Q23.Why does benzene undergos electrophilic substitution more readily than nucleophilic with
difficulty?
4M
Q 24. Account for the following :
1.Alkali metals are good reducing agents.
2.Alkali metals are used in photoelectric cells.
3.LiCl is predominantly covalent while NaCl is ionic .
4.Lithium on being heated in air mainly forms the monoxide not peroxide.
5.BeCO₃ is less stable than MgCO₃.
OR
Complete the following reactions :
6Li + N₂
________________
Na + O₂
LiCO₃
∆
Al(OH)₃ + 3NaOH
ZnSO4 + 2NaOH
________________
________________
+ _________________
________________
________________ + ____________ 5M
Q 25.
1. Why does borontrifluoride behave as a lewisacid ?
2. Is boric acid a proticacid ?Explain ?
3. What happens when boric acid is heated ?
4. How would you explain the lower atomic radius of Game as compared to Al ?
5. What do you mean by inert pair effect ?
OR
Give reasons :
1. Conc. HNO3 can be transported in aluminiumcontainers .
2. A mixture of dilute NaOH and aluminium pieces is used to open drain .
3. Graphite is used as lubricant.
4. Diamond is used as an abrasive.
5. Aluminium alloys are used to make aircraft body.
5M
Q 26. Differentiate between the principle of estimation of nitrogen in organic compound by :
1. Dumas method
2. Kjeldahis method
OR
Explain the term inductive and electromeric effects. Which electron displacement effect explain
the following correct order of acidity of carboxylic acids ?
 Cl3COOH>ClCHOOH>ClCH2COOH
5M
Answer Key
Ans1:- N3-> O2-> F-> Na+> Mg2+> Al3+1
Ans2: 1mark for correct answer
1
Ans3:-1mark for correct answer
1
Ans4:- CO(g) + 2H2(g) →∆CH3OH(l)
1
Ans5:- the enrichment of water by nutrients is known as eutrophication, this causes excessive
growth of algae in water
1
Ans6: molarity = 3M
Mass of NaCl in 1 litre solution = =3x58.5 = =175.5g
1/2
Mass of 1L solution = 1000xdensity
=1000x1.25 = 1250g
1/2
Mass of water in solution = 1250 – 175.5 = 1074.5g
1/2
Hence. Molality(m) = moles of solution / mass of solvent in kg
= 3/1.0745 = 2.79m½
Ans7:- the bond moment of two C═O bonds in CO2 cancel each other indicating the linear
structure
Foue CO2. The resultant u for H2O is ≠ 0 this indicates best structure for H2O molecules because
bond moment of two O-H bonds do not cancel out.
1
O
O
C
O
H
H
1
H
Resultant µ = 0
Resultant µ =1.84D
Ans 8:Ans15:- Autoprotolysis refers to self ionisation of water
H2O(l) + H2O(l) ↔ H3O+ (aq) + OH- (aq)
1/2
Acid1
Base2
Acid2
Base1
Due to autoprotolysis, water acts as amphoteric substance. It acts as a base towards acid stronger
than itself and as an acid towards bases stronger than itself.
1/2
+
Ex. H2O(l) + H2S → H3O +
HS
Acid1
Base2
Acid1
Base2
1/2
+
H2O(l) + NH3(aq) → NH4 (aq) +
OH (aq)
Acid1
Base2
Acid2
Base1
1/2
Ans9:- Green chemistry:- is a way of thinking and utilizing the existing knowlwdge and principal
of chemistry and other science to reduce the advverse impact on environment.
1
The success in the objectives of green chemistry can be achieved by
More efficient use of the raw materials so that less wastage is generated
Search for new alternatives which are environmentaly friendly.
1
Ans 10:
5-methylhept-3-en-1-ol.
2-ethyl-4-methylhexan-1-ol.
2M
Ans11:-a) 40g of calcium contains= 6.023x1023atoms.
1/2
4g of calcium contains= (6.023x1023/4)x4 = 6.023x1022atoms.
1/2
23
Now
6.023X10 atoms of Na have = 23g
1/2
6.023X1023 atom of Na have (23/6.023x1023)x6.023x1022
1/2
= 2.3g
b) 2 (TWO)
1M
Ans12:-a) the longest wavelength corresponding to minimum energy (∆E)transition for balmer
series this transition from n2=3 n1 = 2
1/2
2
2
-1
‾v = 109677(1/n1 -1/n2 )cm
1/2
= 109677 [1/(2)2 – 1/(3)2 ]
1/2
-1
4
-1
=15233 cm = 1.5233x10 cm .
½
b) total electrons when n=4 are 32 but 16 electrons have ms= -1/2.
1M
Ans13:- a) sp3d
1
The longer nature of axial bond is due to relative stronger repulsive interaction
experienced by axial bond as compare to equitorial bonds
1
b) BeCl2=linear
SiCl4=tetrahedral
1M
Ans14:Substance oxidised →HCHO
1/2
Substance reduced →[Ag(NH3)2]+
1/2
+
Oxidising agent →[Ag(NH3)2]
1/2
Reducing agent →HCHO(aq)
1/2
Ans15:- According to heisenberg’s uncertainity principle
∆x.∆p = h/4π
∆x.m∆v = h/4π
1/2
M = h/4π∆x.∆v
1/2
-34
2 -1
-2
24
-1
= 6.626x10 kgm s /4x3.14x10 x5.27x10- ms
= 1.00x10-9 kg
1
Ans16:Due to extra stable half filled electronic configuration of N.
1
Nuclear charge in Cl- = 17
1
+
Nuclear charge in K = 19
Hence ionic size of K+ is amaller than ClIn noble gas ns and np subshell are fully filled therefore they are highly stable. Hence
they donot have tendancy to accept e1
Ans17:- relative stability depends upon bond order
O2= 2.0 , O2+ = 2.5 , O2- =1.5
1 +1/2
+
Hence
O2 > O2 > O2
Magnetic properties O2 , O2+& O2- = paramagnetic
1 +1/2
Ans18:- ∆Hө = ∆Uө + ∆n(g)RT
∆Uө= - 10.5 KJ
∆H(g) = 2-3 = -1mol
-3
T= 298K
R = 8.314x10 KJmol-1K-1
ө
∆H = -10.5 +[-1x8.314x10-3298]
= -10.5 – 2.478 KJ
= 12.978 KJ
According to gibb’s helmholtz equation
∆Gө = ∆Hө - T∆Sө
∆Gө = - 12.978 - 298x(-0.044)
= +0.134 KJ
Since ∆Gө is positive, the reaction is non – spontaneous.
Ans19:(a) decrease
(b) increase
(c) increase
Ans20:Ka x Kb = Kw
Kb = Kw/Ka
The conjugate base of HF is FKb = 1 x 10-14/6.8 x 10-4 = [1.5 x 10-11]
The conjugate base of HCOOH is HCOOKb = Kw/Ka(HCOOH) = 1 x 10-14 / 1.8 x 10-4 = [5.6 x 10-11]
The conjugate base of hcn is CNKb(CN-) = Kw/Ka(HCN) = 1 x 10-14 / 4.8 x 10-9 = [2.1 x 10-6]
Ans21:Species
Conjugated Acid
H2O
H3O+
HCO3H2CO3
HSO4H2SO4
1/2
1/2
1
1
1
1
1
Conjugated Base
OH1
CO321
SO421
b) Due to surface tension
1
Ans22:-1 Mark for correct order
1 Mark for correct reason
1 Mark for comparison between s-character and electronegativity
Ans23: benzene has high electron density due to the presence of 3 pi electron pairs ( 6 pi
electrons ) above and below the plane of the ring representing double bond . due to rich source
electrons benzene attracts the electrophile ( electron-dfficient ) reagents towards it and repel
nucleophile ( elecron rich ) reagents therefore benzene undergoes electrophilic substitution
reaction eaisly and nucleophilic substitution with difficulty.
4M
Ans24:(a)alkali metals have very low ionisation enthalpy. Hence they can lose their valence electron
readily and can bring about reduction
1
(b)alkali metals because of their low ionisation enthalpy can lose electron easily on irradiation ,
hence they are used in photoelectric cells
1
(c)lithium ion, due to it smaller size, has greater polarising power than sodium ion, hence LiCl
predominatingly is covalent while NaCl is ionic.
1
(d) Li+ ions is smaller in size it is stabilized more by smaller anion oxide ion(O2-) as compare to
larger anion peroxide (022-)
1
(e) Be2+ ion is smaller in size than Mg2+ ion.
Be2+ion does not form stable lattice with carbonate ion which is quite larger in size. Mg2+ ion
being larger forms relatively stable lattice with cabonate ion.
1
Or
(a) 6Li + N2→ 2Li3N
(b) Li2CO3 → Li2O + CO2
(c) 2Na + O2 → Na2O2
(d) Al(OH)3 + 3 NaOH → Na3[Al(OH)6]
Sodium aluminate
(e) ZnSO4 + 2NaOH → Zn(OH)2 + Na2SO4
White ppt
Ans25:(a) The B atoms in BF3 has only 6 electrons in the valence shell and thus need two more
electrons to complete its octet. Therefore it easily accepts a pair of electrons from nucleophiles. 1
(b) Boric acid is not a protic acidsince it does not ionize in H2O to give proton it accept a lone
pair of electrons from oxygen atom of the H2O
1
(c) H3BO3∆→ 370k HBO2 + H2O
Boric acid
Metaboric acid
1
4HBO2410k→ H2B4O7 →∆ 2B2O3 + H2O
(d) Due to poor sheilding effect of the valence shell electron of Ga by the inner 3d electron
the effective nuclear charge of Ga is greater in magnitude than Al
1
(e) The group[ oxidation state minus 2 of a group are stable due to non involvement of ns2
orbital of heiver member in bond formation hence ns2electrons remain inert. This effect is
known as inert pair effect.
1
Or
(a) Al reacts withconc. HNO3 to form very thin film of aluminiumoxide on its surface which
protects it from further action.
2 Al + 6conc.HNO3 → Al2O3(s) + 6NO2(g) + 3H2O(l)
Alumina
1
(b) NaOH reacts with Al to evolve dihydrogen gas which high pressure is enough to open
clogged drains.
1
(c) Graphite has layered structure in which different layers had together by weak van der
waal’s forces and hence can be made to slip over one another therefore graphite acts as a
lubricant.
1
(d) Diamond is very hard because it is network solid and hence can be used as an abrasive
(e) Aluminium alloys such as duraluminium is light , tough , and resistant to corrosion and
hence is used to make aircraft body
1
Ans26:(a) In Duma’s method:- a known mass of the organic compound is heated with exess of CuO
in an atmospherre of CO2when notrogen of of the organic compound is converted to N2
gas. The dinitrogen gas is collected over water. The volume of N2 thus obtained is
converted into STP and the % of nitrogen determined by applying the equation
%N = (28/22400) x (vol. of N2 at STP/mass of the substance taken)x100
2+1/2
(b) In Kjeldahl’s method:- a known mass of the organic substance is heated with conc.
H2SO4 in the presence of K2SO4 and little CuSO4 or Hg catalyst in long necked flask
called Kjeldahl’s flask when nitrogen present in the organic compound is quantitavely
converted into (NH4)2SO4 Ammonium Sulphate thus ontained is boiled with excess of
NaOH solution to liberate NH3 gas which is absorbed in a known excess of standard acid
such as H2SO4 OR HCl.
The volume of acid unused is found by titration against a standard alkalisolution from the
volume of the acid used the % of nitrigen is determined by applying the equation
%N = (1.4 x Molarity of acid x Basicity of the acid x volume of the acid used) / (Mass
of the subatance taken)
2+1/2
OR
INDUCTIVE EFFECT:- permanent dispalacement of the electrons along the carbon chain ehen
some atom or group of atoms with different electronegatively than carbon is attracted to carbon
chain is called inductive effect
1
ELECTROMERIC EFFECT:- The complete transfer of the shared pair of π electrons of a
multiple bond to one of the atoms in the presence of the attacking reagent is called electromeric
effect.
1
(a) The given order of the acidic character is explanable on the basis of – I effect
More the number of haloge atoms greater is the – I effect
1/2
and hence more polar is O-H baond i.e. is more as the number of halogen atoms decrease
the polarity of O-H bond decrease hence acidic character
1
The given order of the acidic character is explanable on the basis of + I effect
1/2
(b)As the number of alkyl group increases the + I sffect increases and hence acid strength
decreases accordingly.
MODEL PAPER-4
CLASS-XI(2016-17)
SUB-CHEMISTRY
TOTALMARKS-70
General Instructions :
1.
All questions are compulsory
2.
Q1 to Q5 are very short questions each carry 1 mark.
3.
Q6 to Q10 are short questions each carry 2 marks.
4.
Q11 to Q22 short answer questions and carry 3 marks.
5.
Q23 is value based questions and carry 4 marks.
6.
Q24 to Q26 are long questions and carry 5 marks.
7.
Use log tables if necessary and calculators are not allowed
1. Find the bond order of the following
(a) N2+
2.
(b) O2-
What coul be the IUPAC name and symbol for the element with
Z = 118 ?
3.
Why rain drops are spherical in shape ?
4.
State LechatlearPrinciple ?
5.
How can you separate a mixture of camphor an d common salt
6.
Write electronic configuration of
(i)
7.
Copper
(ii) Chromium
Write the quantum numbers of vahency electrons of
(i) Rubidium and
8.
(ii) Scandium
Distingush between sigma and pi bond ?
Or
Find the number of signma and pi bonds in
(i)
Ethyne and
(ii) Benzene
9.
(a) In what way Lithium shows similarities to Magnesium in its Chemical
behavior
(b)Potasium Carbonate Canotbe Prebared by SolvaysProcess,Why ?
10.
What do you understand by
(a) antiMarkonikott’s rule (b) Hund’s rule
11.
(a)
Ionisationenthelph of Phophorus is more than sulphur why ?
(b)
What compound is formed when Magnesium is burnt in Nitrogen
at mosphere
(c
Which of the following is smallest in size? Why
Fe,
12.
Fe+2, Fe+3
(a) What is Limiting reagent ?
(b)
(i)
2 Mole of A + 3 mole of B
(ii)
300 atoms of A + 200 moleculer of B
(iii)
5 mole of A + 2.54 mole of B
(iv)
6 gm of carbon + 2 gm of Hydrogen
13. What is the wave lengh of light emihed when the electron in an atom
undergoes transition from n=5 to n=2. In which region if falls.
14.
(a) Discuss the shape of the molecules based on VSEPRT
(i) PCl5
(ii) XeO3
(b) Which out of NH3 and NF3 has high dipole moment ?why
15.
(a) Write Vander waals equation for 3 moles of a gas
(b) What are the conditions under which real gar show ideal behavlour.
(c) Critical temperature of CO2 and CH4 are 31.10C and -81.90C respectively.
Which of these has strong intermolecular forces &why?
16.
(a) Write the conditions in terms of ∆H and ∆S when a reaction would
always spontaneous.
(b) For the reaction at 298 K
2A +B  C
∆H = 400 KJ mol-1 8∆S = 0.2KJmol-1 k-1 At what temperature will
the reaction become spontaneous?
17. How do you find Lattice energy of Sodium Chloride by applying BornHaber Cycle (explain with cycle)
Or
Enthelpies of formation of CO(g) CO2(g), N2O(g) and N2O4(g) are -110, -398, 81
and 97 KJ mol-1 respectively. Find the value of∆rH for the reaction.
N2O4(o) + 3CO(g)  N2O (g) + 3CO2 (g)
18.
(a) Assign Oxidation number to the underlined elements.
(i) K2Cr2 O7
(iii) HNO4
(b) Indentify the Oxidising agent and Reducing agent in the following
Reactions
Cu0+ H2 Cu + H2O
(c) Given an example of disproportion reaction ?
19.
(a) What causes the permanent harness of water? Mention one method to
remove permanent hardness?
(b) What do you understand by electron deficient hydrides? Give
examples.
(c) Complete the following chemical reaction
Pbs + H2O2 __________
20.
(a) The mobilites of the alkali metal ions in aqueous solutions are
Li+< Na+< K+<Rb+< Cs+ why
(b) Complete the following chemical reaction
∆
Li2 CO3  _____________
(c) What are the uses of Baking soda
21.
Draw resonance structures of (1)phenol& (2)nitro benzene ?
22.
(a) What do you understand by positional isomers? Give an example
(b) Why is an organic Compound fused with sodium in Lassaigne’s test?
(c) What is the formula of Prussian blue formed in Lassaignes Test ?
23.
Students are facing a lot of Problems in public places due to Cigarette
smoking
(a) Which gas of carbon enters into the lungs of smoker.
(b) What is second hand smoking
(c) As astudents how do you stop the cigarate smoking by a smoker.
(d) What deceases we will get by smoking.
24.
For the reaction
N2(g) +3H2(g) ⇌ 2NH3(g)+ heat
The equilibrium constantKc = 0.50 at 673K
(a) Write the expression for Kp and Kc
(b) What will be equilibrium constant for reverse reaction at same
temperature
(c) What is the effect of yield of NH3
(d) What is the effect of addition of N2(g) and H2(g) On the yield of
NH3
(e) What is the effect of increasing pressure on the yield of NH3
or
(a) Classify the following species into levis acids and bases
OH-,
BF3, H+, F(b) Calculate the PH of 0.02M KOH
(c) H2O can base, write its corresponding conjugate base and
conjugate Acid.
25.
(a) Suggest a reason why Co is poisonous
(b) BCl3 has zero dipole moment why?
(c) Boron is Unable to form BF63-, why ?
(d) Is boric acid is a protic acid
(e) Why Aluminium alloys are used to make aircraft body ?
Or
(a) What is the hydrisation of carbon in (a) CO3-2 (b) diamond
(c )Graphite
(b) Draw and explain the structure of di borane B2H6
(c) What is inorganic benzene? Why it is so called?
26.
(a) Write the chemical equation for Wurtz’s reaction
(b) Write the IUPAC name for
HOOC---CH2-CH2-COOH
(c )Write Chemical equation for freidel craft’s acylation
(d) What happens when Ethyne is subjected to Ozonylsis followed by
hydrolysis in preserve of zinc give equation
(e) Give equation for reaction of Ethyne with sodium
Or
(a) n- pentane has high b.p than neo-pentane why ?
(b) Write the structure of 3,4 di-methy hept-3-ene
(c) Draw the structures of cis and trans isomers of hex-2-ene
(d) Give an example for pyrolysis
(e) Give an example for kolbe’s electrolysis.
MARKING SCHEME
1.
(a) 2.5
(b) 1.5
(½ + ½ )
2.
ununoctoum& UUO
(½ + ½ )
3.
Due to Surface tension
(1)
4.
Def
5.
Sublimation(1m)
6.
Cu ( z=29)
[Ar]
4s1 3d10 ( 1m )
Cr ( z=24)
[Ar]
4s1 3d10 ( 1m )
( 1m)
7.
(i) Rb ( 5,0,0, ½ ) (ii) Sc ( 4,0,0, ½ ) ( 1m + 1m)
8.
Any two difference ( 2m)
8.
9.
( 1m + 1m)
(a) Any two similarities (1m)
(b) KH SO4 is Soluble in water (1m)
10.
(a) def (1m) with example
ē system whose n=0,1,2,3….. (1m)
11.
(a) Due to hal filled p-orbitals 1m
(b) Mg3 N2 (1M)
(c) Fe3 +Due to strong attractions (1m)
12.
(a) Def (1m)
(b) (i) 2 mole of A ½
(ii) 200 mole of B ½
(iii) 2.5 mole of B ½
(iv) 6g of c ½
13.
 = 6.91 x 1011 H2 (2M)
 = 434 nm (1m)
14.
(a) Trigonal bi pyramidal (b) Pyramid (2m)
(b) NH3 more  due to vector sum (1m)
15.
(a) (
) (V-3b) = 3RT (1m)
(b) At high temp & pressure (1m)
(c) CO2 due to high critialtemp (1m)
16.
(a) ∆G = ∆H - T∆S
High T, Low ∆S and High ∆H
(b) ∆G = ∆H- T∆S
1M
Let ∆G =0
0= 400 –T (0.2)
200
=T
0.1
T= 2000 K
Above 2000k
17.
1M
Drawing Born-Haber Cycle and during Lattice energy in term of expertel
value 9 each step 1/2m)
Or
17.
∆H = - 777.7 KJ Mole -1( each step 1M)
18.
(a) + 6 (b) + 5
(½ + ½ )
(b) Oxidising agent = Cuo (½ + ½ )
© Any example (1M)
19.
(a) Due to presence of sulphides and chlorides of Magnesium or calcium
salts Calgons method (½ + ½ )
(b) Less than Octet at central atom
B2H6
(½ + ½ )
(c) Pbs + H2 O2 Pbso4 + H2O (1M)
20.
(a) Due to hydration (1M)
(b) Li2Co3 Li2 O + Co2 (1M)
(c) (i) Neutralises acidity of (½ + ½ )
(ii) In stomach, fire extinguisher
21.
Writing resonance structures of phenol & nitro benzene
22.
(a) Def with suitable example (½ + ½ )
(b) To convert organic to inorganic compounds (1M)
(c) Fe4[ Fe (CN)6)3
(1M)
FerriferroCyanide formula
23.
(a) CO
(b) Inhaling smoke of active smoker
(c) Any Good suggestion
(d) Lung Cancer, Heart disease (1Mx4)
24.
(a) Kp = Kc (RT)+2
(b) Kc =
=2 (1Mx5)
(c) Yield decreases
(d) Yield increases
(e) Increases
Or
24.
(a) Lewis Acids
:
BF3, H+
Lewis bases
:
OH-, F-
(b)
PH= 14 – POH
POH= log ( 2x10-2)
1M
(1.5 &1.5 )
POH= log 2+2
PH= 14+log2-2
=12+0.3010
=12.3010
(2M)
(c) H2O accepts as well as donate H+ hence it acts on both acid & base
H3O+  H2OOHConjugate acid
25.
(2M)
Conjugatebase
(a) Co forms a complex with Fe+2 in hemoglobin
(b) Due to vector addition
(c) Due to lack of d-orbitals
(d) No it captures one OH- from water &release H+
B (OH)3+H2O [ B(OH)4]- + H +
(e) They are light and strong
(1mx5=5)
Or
(c) Sp2
(a) Sp2
(b) Sp3
(3M)
(b) Drawing & explaining B2 H6
(1 M)
(c) B3 N3 H6 as it is analogous to the structure of benzene
(1M)
26.
26.
(a) R-X+2Na+x-R R-R( in dry ether)
(b) 1,4-di – butanoic acid
(c) C6H5- H+Cl-C-C6H5 C6H5 - C-C6H5( In presence of AlCl3
(d) We get two mole of methanol
(e) H-CC-H+NaH-CC-Na+½ H2
Or
(a) Due to strong Vader waals forces.
+ + +
6
5
4 3 2
1
(b) H3 C- H2C-C C-CH-2 CH3
I
I
CH3CH3
(1M)
(c) Writing cis& trans isomers
(d) C2 H6 CH2 CH2 + H2
(e) Potassium Male ate Aqueous solution subjecting to electrolysis
Produces ethene
MODEL PAPER-5
CLASS-XI(2016-17)
SUB-CHEMISTRY
TOTALMARKS-70
General Instructions :
1.
All questions are compulsory
2.
Q1 to Q5 are very short questions each carry 1 mark.
3.
Q6 to Q10 are short questions each carry 2 marks.
4.
Q11 to Q22 short answer questions and carry 3 marks.
5.
Q23 is value based questions and carry 4 marks.
6.
Q24 to Q26 are long questions and carry 5 marks.
7.
Use log tables if necessary and calculators are not allowed
1. What would be the IUPAC name and symbol for the element with atomic no 119.
2.
3.
4.
5.
6.
7.
What is the difference between molarity and molality?
Drop of liquid assumes spherical shape. Why?
State Henry’s law?
Name the adsorbent commonly used in adsorption chromatography.
State Heisenberg’s Uncertainty principle. Give mathematical expression for the same.
I) How many subshells are associated with n = 4?
II) How many electrons will be present in the sub shells having msvalue of -1/2 for n = 4?
8. Calculate bond order for O2 molecule. Predict its magnetic nature.
OR
Differentiate between bonding and anti-bonding molecular orbitals.
9. Write chemical equations involved in the preparation of NaHCO3 by Solvay process.
10. Give an example for each of the following.
I) Wurtz reaction ii) Markonikovs addition reaction
11. Explain the following.
i) Sodium is less reactive than Potassium.
ii) A solution of Na2CO3 alkaline.
iii) LiF is almost insoluble in water whereasLiCl soluble in water.
12.3 g of H2 react with 29 g of O2 to yield H2O.
i) What is the limiting reagent?
ii) Calculate the maximum amount of water that can be formed.
iii) Calculate the amount of one of the reactants which remain unreacted.
13. A photon of wavelength 4x107 m strikes on a metal surface, the work function of metal being
2.13 eV.Calculate i) the energy of photon. ii) The kinetic energy of emission. iii) The velocity of
photo electron. (1 eV = 1.6020x10-10J)
14. Predict the shapes of the following molecules by using VSEPR Theory: SF4, SF6 and NH3.
Draw their shapes also.
15. Derive Ideal gas equation. At 250C and 760 mm of Hg pressure, a gas occupies 600ml
volume. What will be its pressure at a height where the temperature is 100C and the volume of
the gas is 640 ml?
16. i) for the reaction: 2Cl(g) Cl2(g) : What will be the sign of ∆H and ∆S ?
ii) The equilibrium constant for the reaction is 10. Calculate the value of ∆Gө. Given R= 8 J
K mol-1 : T= 300K.
-1
17.i) State First law of thermodynamics. Give mathematical expression for it.
The enthalpy of formation of methane at constant pressure and at 300K is -78.84kJ. What
will be the enthalpy of formation at constant volume?
ii)
OR
i) State Hess’s law of constant summation.
ii) Calculate standard enthalpy of formation of CH3OH (l) . Given that enthalpy of
combustion of CH3OH (l) is -726 kJ/mol , enthalpy of formation of CO2 (g) and H2O (l)
are -393 kJ/mol and -286 kJ/mol respectively.
18. i) Write the formula of the following compounds a) mercury (II) chloride b) tin (IV) oxide.
ii) Balance the following redox reaction in acidic medium.
MnO4- + SO2
-----------Mn
+2
19. Complete the following:
+HSO4-
i) PbS +H2O2
--ii)
CaO + H2O -
iii) Ca3N2 + H2O----
20. What is diagonal relationship? Write similarities between Li and Mg.
21. i) Write bond line formulas for a) 2, 3- dimethylbutanal b) Heptane-4-one.
ii) What are nucleophiles and electrophiles? Explain with examples.
22. i) Explain chain isomerism with suitable example.
ii) 0.3780 g of an organic compound gave 0.5740 g 0f silver chloride in Carius estimation.
Calculate the percentage of Chlorine in it?
23. TajMahal is a great historic monument in India. It has lost its luster due to pollution in the
air.
i) What is the main reason for damage done to TajMahal?
ii) How is damage actually caused?
iii) Suggest any two measures to check the pollution.
24, At 473K, the equilibrium constant Kc for the decomposition of PCl5is 8.3X10-3. If
decomposition proceeds as;
PCl5 (g)
i)
ii)
iii)
iv)
PCl3 (g)+ Cl2(g) ∆H = + 124.0 kJ/mol.
Write an expression for Kc for the reaction.
What is the value of Kc for the reverse reaction at the same temperature?
What would be the effect on Kcif a) more PCl5 is added b) Temperature is increased?
State Lechatelier’s principle.
OR
i)
ii)
iii)
Define Lewis concept of acids and bases? Classify the following species into Lewis acids
and bases: OH-, F-,H+,BF3.
Calculate PH of 0.003 M HCl solution.
Both H2O and NH3 can act as both Bronsted acid and base. For each case give the
corresponding conjugate acid and base.
25. Give reasons:
i) Conc. Nitric acid can be transported in aluminum container.
ii) CO2 is a gas whereas SiO2 is solid.
iii) PbCl2 is more stable than PbCl4
iv)CO is poisonous in nature.
v)Graphite is used as lubricant.
OR
What do you understand by a) Inert pair effect b) allotropy c) catenation?
Explain the structure of diborane.
26. i) Give one example for each of the following.
a) Ozonolysis of alkenes.
b) Markonikov’s addition. c) Fridelcrafts alkylation.
ii) Draw the structures of cis-trans isomers of 2- butane.
Write the IUPAC name of CH3CH=C(CH3)2.
OR
What are necessary conditions for a system to be aromatic?
An alkene ‘A’ upon ozonolysis gives a mixture of ethanal and pentan-3-one.Write the
structure and IUPAC name of ‘A’
MARKING SCHEME
Q.NO.
VALUE POINTS
Ununennium&Uue½ & ½
Definitions or mol/lit &mol/kg
due to surface tension
statement
silica or SiO2
Statement & mathematical expression
Four subshells & 16 electrons
Bond order 2 & paramagnetic
Or
Any two differences
9. Correct chemical equations
10. One example for each reaction
11. i) due to larger size or low ionization enthalpy
ii) Due to hydrolysis of carbonate ions
iii) Due to covalent nature of LiF1
12. I) Hydrogen
ii) 27 g of water
iii) 5 g of oxygen
13. I) E = hc/λ = 4.97x 10-10 j or 3.1 ev
Ii) K.E = (3.1 - 2.13) = 0.97 ev1
iii) Velocity of photo electron = 0.34x10-12m2s-1
14. See saw, octahedral and pyramidal
15. Derivation
Formula & substitution
Answer with units
1.
2.
3.
4.
5.
6.
7.
8.
MARKS
1
1
1
1
1
1+1
1+1
1+1
1+ 1
2
1+1
1
1
1
1
1
1
1
1+1+1
1
1
1
16. ∆H and ∆S are negative
Formula and substitution
Correct answer
17. Statement and mathematical expression
Formula and substitution
Correct answer
OR
Statement
Correct formula
Answer with units
18. Correct formulas
Correct balanced oxidation and reduction reactions
Net balanced equations
19. correct balanced equation
20. Statement
Any two similarities
Definition with example
21. Definition with formula
22. sample
Formula and substitution
Correct answer
23. Due to acid rain
Acids present in the rain water react with marble
To use LPG and CNG fuels
Not to issue licenses for the industries causing pollution
24.
Expression for Kc
Calculation of Kc for reverse reaction
No change in Kc
Kc increases
Statement
OR
Definitions
Classification
Calculation of PH
Correct formula for conjugate acid and base for each
25. Correct reason for each 1 mark
1
1
1
1
1
1
1
1
1
1
1
1
1+1+1
1
1+1
1+1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1+1
5
OR
Definitions for each 1 mark
3
Structure of diborane
1
Brief explanation of structure
1
26. Correct example for each 1 mark
Correct structures
Correct IUPAC name
3
1
1
OR
Planar structure
1
Resonance or conjugation
1
Obey Huckels rule
1
Correct structure
1
Correct IUPAC name
1
MODEL PAPER-6
CLASS-XI(2016-17)
SUB-CHEMISTRY
TOTALMARKS-70
General Instructions :
1.
All questions are compulsory
2.
Q1 to Q5 are very short questions each carry 1 mark.
3.
Q6 to Q10 are short questions each carry 2 marks.
4.
Q11 to Q22 short answer questions and carry 3 marks.
5.
Q23 is value based questions and carry 4 marks.
6.
Q24 to Q26 are long questions and carry 5 marks.
7.
Use log tables if necessary and calculators are not allowed
1. Calculate the mass percentage of different elements present in CaCO3.
2. What is the lowest value of n that allows g orbital to exist?
3. Why do elements in the same group have similar physical and chemical properties?
4. Name a suitable technique of separation of the components from a mixture of calcium sulphate
and camphor.
5. Write the IUPAC name of CH2=CH-C≡C-CH3
6. For the reaction, 2Cl(g) → Cl2(g), what are the signs of ΔH and ΔS? Why?
7. (a) The equilibrium constant expression for a gas reaction is Kc = [NH3]4 [O2]5
[NO]4 [H2O]6
Write a balanced chemical equation corresponding to this expression.
(b) Write the relationship between Kp and Kc.
8. Fluorine reacts with ice and results in the change H2O(s) + F2(g) HF(g) + HOF(g)
Justify that this reaction is a redox reaction
9. Give condensed and bond line structural formulas for: (a) 2,2,4-Trimethylpentane
(b) 2-Hydroxy-1,2,3-propanetricarboxylic acid
10. Draw the cis and trans structures of hex-2-ene.
(OR)
Write chemical equations for combustion reaction of the following hydrocarbons:
(i) Butane (ii) Pentene
11. Calcium carbonate reacts with aqueous HCl to give CaCl2 and CO2 according to the reaction,
CaCO3 (s) + 2 HCl (aq) → CaCl2 (aq) + CO2(g) + H2O(l)
What mass of CaCO3 is required to react completely with 25 mL of 0.75 M HCl?
12. The wavelength range of the visible spectrum extends from violet (400 nm) to red (750 nm).
Express these wavelengths in frequencies (Hz). (1nm = 10–9 m)
13. Using s, p, d, f notations, describe the orbital with the following quantum numbers
(a) n = 2, l = 1, (b) n = 4, l = 0, (c) n = 5,l=3
14. Use the periodic table to answer the following questions.
(a) Identify an element with five electrons in the outer sub shell.
(b) Identify an element that would tend to lose two electrons.
(c) Identify an element that would tend to gain two electrons.
15. (a) Define hydrogen bond. (b) What are its types?
(c) Is it weaker or stronger than the van der Waals forces?
16. At 25°C and 760mm of Hg pressure a gas occupies 600 mL volume. What will be its
pressure?
at a height where temperature is 10°C and volume of the gas is 640 mL.
17. Density of a gas is found to be 5.46 g/dm3 at 27 °C at 2 bar pressure. What will be its
density?
at STP?
18. Predict in which of the following, entropy increases/decreases: (i) A liquid crystallizes into a
solid. (ii) Temperature of a crystalline solid is raised from 0 K to 115 K. (iii) H2(g)  2H(g)
19. Given the standard electrode potentials, K+/K = –2.93V, Ag+/Ag = 0.80V, Hg2+/Hg = 0.79V
Mg2+/Mg = –2.37V. Cr3+/Cr = –0.74V, Cu2+/Cu = 0.34V. Arrange these metals in their
increasing order of reducing power.
20. Complete the following reactions
(a) CO + H2  __________
(b) Zn + H2O  ______ (c) C3H8 + 3H2O  _____
21. Discuss the various reactions that occur in the Solvay process.
22. 0.3780g of an organic chloro compound gave 0.5740g of silver chloride in Carius estimation.
Calculate the percentage of chlorine present in the compound.
(OR)
Give a brief description of the principles of the following techniques taking an example in
each case - (a) Crystallization (b) Distillation (c) Chromatography
23. Arun has developed a compost pit in his garden. His sister doesn’t like it because of the bad
odour and nuisance of flies. Whom do you support Arun or his sister? Why? How can you
help Arun’s sister if you support Arun?
24. (a)Write the relationship between equilibrium constant K, reaction constant Q and Gibb’s
energy G.
(b)Write the spontaneity of the reaction when ΔG= +ve and ΔG = -ve
(c) Equilibrium constant Kc for the reaction, Sucrose + H2O  Glucose + Fructose is 2x1013
at 300K. Calculate ΔG0 at 300K.
(OR)
Define (a) Common ion effect.(b) Buffer solutions- (c) pH
25. Give reasons:
(i) Conc. HNO3 can be transported in aluminium container.
(ii) Graphite is used as lubricant.
(iii) Diamond is used as an abrasive.
(iv) Aluminium alloys are used to make aircraft body.
(v) Aluminium utensils should not be kept in water overnight.
(OR)
What happens when
(a) Borax is heated strongly,
(b) Boric acid is added to water,
(c) BF3 is reacted with Lithium Aluminium Hydride,
(d) BF3 is reacted with ammonia,
(e) Boric acid is heated?
26. Write the reaction between (a) hex-1-ene and HBr (i) in the absence of peroxide (ii) in the
presence of peroxide (b) propene and Ozone (c) Calcium carbide and water (d) Bromo
methane and sodium
(OR)
Explain the following reactions with respect to Benzene
(a) Nitration with nitrating mixture (b) Sulphonation (c) Alkylation (d) Acetylation
(e) Halogenation in presence of AlCl3.
Scoring key
Q.No Value Points
1.
40g + 12g +48g =100 g
Ca=40% C=12%
O=48%
2.
n=5
3.
The physical and chemical properties of elements depend on the number of
valence electrons. Elements present in the same group have the same
number of valence electrons.
4.
Sublimation
5.
Pent-1-ene-3-yne
6.
The given reaction represents the formation of chlorine molecule from
chlorine atoms. Here, bond formation is taking place. Therefore, energy is
being released. Hence, ΔH is negative.
Also, two moles of atoms have more randomness than one mole of a
molecule. Since spontaneity is decreased, ΔS is negative for the given
reaction.
7.
(a) 4NO + 6H2O 4NH3 + 5O2
(b) Kp = Kc(RT)Δn
8.
The oxidation number of F increases from 0 in F2 to +1 in HOF.
Marks
½
½
1
1
1
1
1
1
1
1
9.
The oxidation number decreases from 0 in F2 to –1 in HF.
F is both oxidized and reduced. Hence, the given reaction is a redox
reaction.
(a) 2, 2, 4–trimethylpentane
Condensed formula:
(CH3)2CHCH2C (CH3)3
Bond line formula:
½
½
1
½
½
(b) 2–hydroxyl–1, 2, 3–propanetricarboxylic acid
Condensed Formula:
(COOH)CC(OH) (COOH)CH2(COOH)
Bond line formula:
½
½
10.
Hex-2-ene is represented as:
Geometrical isomers of hex-2-ene are:
1
1
10.
11.
12.
13.
14.
(i) Butane (ii) Pentene
2C4H10 + 13O2 8CO2 + 10H2O
2C5H10 + 15O2 10CO2 + 10H2O
[(0.75 mol) × (36.5 g mol–1)] HCl = 27.375 g of HCl is present in 1 L.
Thus, 1000 mL of solution contains 27.375 g of HCl.
Amount of HCl present in 25 mL of solution = 0.6844 g
From the given chemical equation,
2 mol of HCl (2 × 36.5 = 71 g) react with 1 mol of CaCO3 (100 g).
Amount of CaCO3 that will react with 0.6844 g = 100/71 x 0.6844 g=
0.9639 g
γ = c/λ =3 x 108m/s /400 x 10-9m = 7.50 x 1014Hz
Frequency of red light = γ = c/λ =3 x 108m/s /750 x 10-9m = 4 x 1014Hz
The range of visible spectrum = 4 x 1014Hz to 7.5 x 1014Hz
(a) 2p (b) 4s (c)5f
F, Cl, Br, I, or At.(any one)
1
1
1
1
1
1
1
1
Each 1
1
15.
16.
Be, Mg, Ca, Sr, Ba. (any one)
O,S, Se, Te, Po (any one)
(a) A hydrogen bond is defined as an attractive force acting between the
hydrogen attached to an electronegative atom of one molecule and an
electronegative atom of a different molecule (may be of the same kind).
(b)(i) Intermolecular H-bond e.g., HF, H2O etc.
(ii) Intramolecular H-bond e.g., o-nitrophenol
(c)Hydrogen bonds are stronger than Van der Walls forces since hydrogen
bonds are regarded as an extreme form of dipole-dipole interaction.
p1V1/T1 = p2V2/T2
p2= (760mm Hg x 600 ml x 283 K) / (640 ml x 298 K) = 676.6 mm Hg
17.
Hence, the density of the gas at STP will be 3 g dm–3.
18.
19.
20.
21.
22.
22.
(a) decreases (b) increases (c) increases
The lower the electrode potential, the stronger is the reducing agent.
Therefore, the increasing order of the reducing power of the given metals
is Ag < Hg < Cu < Cr < Mg < K.
(a) CO + 2H2  CH3OH
(b) Zn + 2H2O Na2ZnO2 + H2
(c) C3H8 + 3H2O  3CO + 7 H2
Solvay process is used to prepare sodium carbonate.
Step 1
2NH3 + H2O + CO2  (NH4)2CO3
Step 2
(NH4)2CO3 + H2O + CO2  2NH4HCO3
NH4HCO3 + NaCl  NH4Cl + NaHCO3
Step 3
NaHCO3 upon heating  Na2CO3 + CO2 + H2O
Given that,
Mass of organic compound is 0.3780 g.
Mass of AgCl formed = 0.5740 g
1 mol of AgCl contains 1 mol of Cl.
Thus, mass of chlorine in 0.5740 g of AgCl = (35.5 x 0.5740)/143.32
= 0.1421 g
Percentage of Chlorine = (0.1421 x 100) / 0.3780 = 37.59 %
(a) Crystallisation
The impure compound gets dissolved in the solvent in which it is
1
1
1
1+1
1
1
1
Each 1
Each
½
Each 1
1
½
½
1
2
1
23.
24.
24.
25.
25.
sparingly soluble at room temperature, but appreciably soluble at higher
temperature. On cooling the solution, the pure compound crystallizes out
and is removed by filtration.
(b) Distillation
It is based on the fact that liquids having different boiling points vaporize
at different temperatures.
(c) Chromatography
It is based on the difference in movement of individual components of a
mixture through the stationary phase under the influence of mobile phase.
I support Arun because he wishes to prepare manure out of the wastes. I
can help Arun’s sister by asking her to cover the compost producing pit in
order to protect ourselves from bad odour and flies. (Any relevant answer
deserves marks)
(a) ΔG = -RTlnK
(b) When ΔG is positive the reaction is not spontaneous
When ΔG is negative the reaction is spontaneous
(c) ΔG = -RTlnK = -2.303RTlog K= -2.303 x 8.314 x 300 x log (2 x 1013)
= -7.64 x 104
(a) Common ion effect- the suppression of degree of dissociation of weak
upon adding a strong electrolyte having common ions between them.
(b) Buffer solutions- The solutions which resist change in pH on dilution
or with the addition of small amounts of acid or alkali are called Buffer
solutions
(c) pH = -log10[H3O+]
(i) Con HNO3 reacts with aluminium to form a thin protective oxide layer
on the aluminium surface. This oxide layer renders aluminium passive.
(ii)The different layers of graphite are bonded to each other by weak van
der Waals’ forces which slide over each other. Therefore, graphite can be
used as a lubricant.
(iii) In diamond, carbon is sp3 hybridised. Each carbon atom is bonded to
four other carbon atoms with the help of strong covalent bonds giving it a
very rigid 3-D structure. So it is very difficult to break diamond.
(iv) Aluminium has a high tensile strength and is very light in weight. It is
very malleable and ductile and can be alloyed with various metals such as
Cu, Mn, Mg, Si, and Zn. Therefore, it is used in making aircraft bodies.
(v) The oxygen present in water reacts with aluminium to form a thin layer
of aluminium oxide. When water is kept in an aluminium vessel for long
periods of time, some amount of aluminium oxide may dissolve in water.
As aluminium ions are harmful, water should not be stored in aluminium
vessels overnight.
a) When heated, borax undergoes various transitions. It first loses water
molecules and swells. Then, it turns into a transparent liquid, solidifying to
form a glass-like material called borax bead.
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(b) When boric acid is added to water, it accepts electrons from –OH ion.
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(c) BF3 is reacted with LiAlH4
Diborane is formed 4BF3 + 3LiAlH4  2 B2H6 + 3LiF + 3AlF3
(d) BF3 (a Lewis acid) reacts with NH3 (a Lewis base) to form an adduct.
This results in a complete octet around B in BF3.
26.
26.
(e) Boric acid is heated
On heating, orthoboric acid above 370K forms metaboric acid, HBO2
which on further heating yields boric oxide, B2O3.
H3BO3 ⎯Δ→ HBO2 ⎯Δ→ B2O3
(a) (i) CH3CH2CH2CH2CH=CH2 + HBr (in the absence of peroxide)
CH3CH2CH2CH2CH(Br)CH3
(a) (ii) CH3CH2CH2CH2CH=CH2 + HBr (in the presence of peroxide)
CH3CH2CH2CH2CH2CH2Br
(b) CH3CH=CH2 + O3  CH3CHO + HCHO
(c) CaC2 + 2H2O  C2H2 + Ca(OH)2
(d) CH3Br + Na + CH3Br  CH3CH3 + 2 NaBr
(a) Nitration with nitrating mixture
C6H6 + Con HNO3/Con H2SO4  C6H5NO2
(b) Sulphonation
C6H6 + Con H2SO4  C6H5SO3H
(c) Alkylation
C6H6 + CH3Cl (in presence of AlCl3)  C6H5Cl +HCl
(d) Acetylation
C6H6 + CH3COCl (in presence of AlCl3)  C6H5COCl +HCl
(e) Halogenation in presence of AlCl3.
C6H6 + Cl2 (in presence of AlCl3)  C6H5Cl
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