Download questions on periodic classification of elements

INDEX
SL NO
01
O2
03
04
05
06
07
08
NAME OF THE TOPIC
PAGE NO
IMPORTANT POINTS ON
2-4
CARBON AND ITS COMPOUNDS
QUESTIONS ON CARBON AND
5-6
ITS COMPOUNDS
ANSWERS ON CARBON AND ITS
7-11
COMPOUNDS
IMPORTANT POINTS ON
12-13
PERIODIC CLASSIFICATION OF
COMPOUNDS
QUESTIONS ON PERIODIC
14-15
CLASSIFICATION OF ELEMENTS
ANSWERS ON PERIODIC
16-19
CLASSIFICATION OF ELEMENTS
VALUE BASED QUESTIONS
20-21
HIGH ORDER THINKING SKILLS
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QUESTIONS
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CARBON AND ITS COMPOUNDS
COVALENT BONDING: Bond formed by mutual sharing of electrons between two atoms so that
both the atoms acquire the stable nearest noble gas configuration.
Covalent Bond is found in compounds formed by non-metals.
Electron dot structure atom and compounds (methane, ethane, ethane, H2O, NH3, &CO2) and
covalent bond formation in H2, N2, O2, CH4, H2O, NH3 &CO2.
VERSATILE NATURE OF CARBON: It is due to two factors noticed in carbon. They are:
1) CATENATION i.e. ability of carbon to form bonds with other atoms of carbon giving rise to
large molecules.
2) TETRAVALENCY i.e. ability of carbon to form bonds with four other atoms of carbon or
atoms of some other mono valent element.
SATURATED AND UNSATURATED CARBON COMPOUNDS:
Saturated hydrocarbons give a clean flame while unsaturated carbon compounds give a yellow
flame with lots of black smoke.
1) COMBUSTION OF HYDROCARBONS: Products are CO2, H2O and heat& light.
e.g. CH4 + O2 ------- > CO2 + H2O + HEAT + LIGHT
CH3CH2OH + O2 --------- > CO2 + H2O + HEAT + LIGHT
2) OXIDATION of ETHANOL
Alkaline KMnO4 + heat
CH3CH2OH ---------------------------------------------------------- > CH3COOH
ETHANOL
Or Acidified K2Cr2O7 + heat
ETHANOIC ACID
Alkaline KMnO4 and acidified K2Cr2O7 are oxidising agents. They oxidise alcohol to acids.
2) ADDITION REACTION
Hydrogenation of unsaturated hydrocarbons
Ni catalyst
e.g. CH2=CH2 + H2 ------------------------------------------------- >
CH3CH3
Hydrogenation of vegetable oils (unsaturated carbon compounds) using a Ni catalyst
give vanaspati ghee.
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3)SUBSTITUTION REACTION:
Saturated hydrocarbons undergo substitution reaction in the presence of sunlight where one
or more hydrogen atom(s) is substituted by other atoms
Sunlight
CH4 + Cl2
------------------------------------------------- >
CH3Cl + HCl.
ETHANOL:
It is a colourless liquid with alcoholic smell. It is neutral towards litmus. It is highly soluble/
miscible with water .
Chemical properties of Ethanol
Ethanol has alcoholic group .(-OH)group. Chemical formula of Ethanol is CH3CH2OH.
Reactions of Ethanol:
1) Ethanol reacts with Sodium metal to form Sodium ethoxide and hydrogen gas is released.
This reaction is used to detect the alcoholic functional group (-OH) in compound.
2CH3CH2OH + 2Na
------------------------------------------- >
Ethanol
2CH3CH2ONa + H2
Sodium ethoxide
Hydrogen
2) When ethanol is heated strongly with Conc. H2SO4 acid to about 443 k, it undergoes
dehydration to form ethane.
Conc.H2SO4
CH3CH2OH ------------------------------------------Heat
>
CH2=CH2 + H2O
Ethene
ETHANOIC ACID (CH3COOH):
Fuctional group is ( -COOH). Common name is Acetic acid. 5-8% Solution of acetic acid in water
is Vinegar.
Reactions of ethanoic acid
1) Esterification Reaction: Carboxylic acid reacts with alcohols in the presence of Conc. H2SO4 to
form ester and water. The reaction is called Esterification.
Ethanoic acid reacts with ethanol in the presence of Conc. H2SO4 to give ethyle ethanoate
(ester ) and water.
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Conc. H2SO4
CH3COOH + CH3CH2OH -----------------------------------
>
CH3COOCH2CH3 + H2O
Ethyl ethanoate (ester)
SAPONIFICATION:
When an ester reacts with NaOH , it gives an alcohol and Sodium salt of Carboxylic acid.
CH3COOC2H5 + NaOH ----------------------------------Ester
>
CH3COONa +
Sodium ethanoate
C2H5OH
ethanol
This reaction is used in the preparation of Soap.
ii) Reaction with a base (Neutralisation Reaction)
Ethanoic acid reacts with NaOH to give Sodium ethanoate (salt) and water.
CH3COOH + NaOH-----------------------------------
>
CH3COONa + H2O
Sodium ethanoate
iii) Reaction with Carbonates and Hydrogen Carbonates:
Ethanoic acid reacts with Carbonates and Hydrogen carbonates to give Salt,CO2 and water .Brisk
Effervescence is observed due to release of CO2.
2CH3COOH + Na2CO3 ----------------------------------CH3COOH + NaHCO3-----------------------------------
>
>
2CH3COON + H2O + CO2
CH3COONa + H2O + CO2
Soaps and Synthetic Detergents:
Distinction in Soaps and Detergents, Advantage of Synthetic Detergents over Soaps
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CHAPTER WISE QUESTIONS
1, Draw the electron dot structure of methane molecule/ethene.
2. Name two elements which are present in both CNG and Petroleum.
3. Draw the structure of Butanone.
4. How many electron pairs are shared between two atoms?
5. Predict the nature of the molecule when two atoms of an element X with electronic configuration
2, 8, 6 mutually Combine.
6. An element X has four valence electrons while an element Y has six valence electrons. What type
of bond is expected to be form between the two? Write the structure of the compound,
7. What is self-linking property of Carbon known as……………………………………..?
8. What is the difference in the molecular formulae of the two consecutive members in a family?
9. Which Catalysts is generally used in the Hydrogenation of oils?
10. Name the functional group present in ethanoic acid/ acetic acid.
11. How will you know whether a particular Hydrocarbon is saturated or unsaturated by flame test?
12, How would you distinguish between ethanol and ethanoic acid experimentally?
13 Which gas is evolved when ethanol is reacted with sodium metal?
14. Which cations are responsible for the hardness of water?
15. What is Hydrogenation? What is its industrial application?
16. Why do burning of oils give a yellow flame with lots of black smoke?
17. What is meant by denatured alcohol? Which substance is added for the denaturation of ethyl
alcohol?
18. Write chemical equation of the reactions of ethanoic acid with
(i)Sodium carbonate, (II) ethanol in the presence of Conc. H2SO4, (iii) NaOH
19. Write the formulae of the compounds and name the functional groups present in each of them
(i) Ethanoic acid (ii) Propanone (iii) ethanol
20. Complete the following equations and write the names of the Products formed
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Alkaline KMnO4
(i)
C2H5OH----------------------------------- >
(ii)
CH3CH2OH + O2-----------------------------------
>
Ni
(iii)
CH2=CH2 + H2----------------------------------Sunlight
(iv)
CH4 + Cl2-----------------------------------
>
>
Conc.H2SO4
(v)
CH3CH2OH----------------------------------- >
(vi)
CH3CH2OH + Na-----------------------------------
>
21. Give reason for the following:a) The element Carbon forms a large number of compounds.
b) Use of synthetic detergents causes pollution problems.
c) An unsaturated hydrocarbon gives a yellow flame with lots of black smoke.
22. An ester has the molecular formulaCH4H8O2.Write its structural formula. How is it prepared?
Write two uses of esters.
23. An organic compound ‘A’ is an essential constituent of wine & beer and has the molecular
formula C2H6O. Upon oxidation the compound ‘A’ gives another compound ‘B’ with formula
C2H6O2.which is present in Vinegar. Identify the compound ‘A’ and ‘B’ . Write the chemical
equation for the conversion of ‘A ‘ to ‘B’ and name the oxidizing agents evolved in the reaction.
24. An organic compound A having molecular formula C2H6O reacts with Sodium metal and evolves
a gas B which readily catches fire . A also reacts with ethanoic acid in the presence of Conc.H2SO4
to form sweet smelling compound C used in making perfumes.
(i) Identify the compounds A , B, and C.
(ii) Write the chemical equation to represent the conversion of (a ) compound A into B
And (b) Compound A into Compound C
25. An organic compound ‘A’ has the molecular formula C2H4O2 when the compound A is added to a
solid B Kept in a test tube. A colourless and odourless gas is released . The gas turned lime water
into milky when passed through it . Identify the the compound A. Predict the nature of compound
B . Write the possible chemical reaction.
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PERIODIC CLASSIFICATION OF ELEMENTS:Dobereiner’s Triads:- When three elements in a triad were written in the order of increasing atomic
masses , the mass of the middle element was almost the average of the atomic masses of the
other two elements , e.g. of triads are (1) Li Na K (2) Ca Sr Ba (3) Cl Br I.
Limitations
1) All the elements known that time could not be arranged into traids.
Newlands’ Law of Octaves: - It states that when elements are arranged in other of increasing
atomic masses ,there is a repetition of the properties of every eight element as compared to the
given element.
Limitations- (i) This classification was applicable only upto the element Calcium. (ii) Sometimes,
two elements were put in the same slot . (iii) After the discovery of noble gases, law of octave is not
valid .
Mendeleev’s Periodic Table :
Mendeleev’s Periodic law : It states that properties of the elements are a periodic function of their
atomic masses .
Basis of classification of elements :
Mendeleev’s classification of elements was based on the atomic masses of the elements and the
formulae of the hydrides and oxides formed by the elements .
Achievements: - (i) Systematic study of the elements. With the classification of elements into
groups and periods, their study became quite systematic. (ii)Prediction of new elements and their
properties. (iii)Correction of doubtful atomic masses.
Limitations:I) Position of Hydrogen. ii) Position of isotopes. Iii) Wrong order of atomic masses of some
elements. Iv) Different groups for similar elements. V) No co-relation of elements in sub groups.
Modern Periodic Law:
Properties of the elements are the periodic function of their atomic numbers.
Periodicity : It may be defined as the repetition of the same valence shell electronic configuration.
Position of Elements in the Modern periodic Table;- (i) The elements present in any one of group
have the same number of valence electrons. (i) Atoms of different elements with the same number
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of occupied shells are placed at the same period. (iii) The number of shells increases by one unit as
we go down the group. (iv) The number of Valence shell electrons increase by one unit on moving
from left to right in a period.
Trends in the Modern Periodic Table:
Valency: Elements present in a group have the same valency.Elements present in the same period
do not show same valency. It is found that along the period, valency first increases from 1 to 4 and
then decreases from 3 to 0.
Atomic Size: It may be defined as as the distance from the centre of the nucleus of an isolated atom
from the outermost shell containing the electrons.
(i) In a group ,the atomic size increases downwards . This is because new shells are being added as
we go down the group . (ii) The atomic size decreases as we move from left to right along a period.
This is due to an increase in nuclear charge which pulls the electrons closer to the nucleus and
reduces the size of the atom
Metallic character:- It is due to electron releasing tendency of the atom. Metals are electropositive
in nature . (i) Down the group ,the metallic character increases due to increase in atomic size. (ii)
Along the period ,the metallic character decreases due to decrease in atomic size. As a result ,the
tendency of the atom to loose electron decreases along the period.
Non – Metallic Character :- The tendency of the atom to gain electron. Non metals are electro
negative in nature .(i) Down the group, the non metallic character decreases because the electron
gaining tendency of the atom decreases due to their increase size. (ii) Along the period, the non
metallic character increases due to their decrease atomic size.
Electro negativity: The tendency of an atom in a molecule to attract the shared electron pair in a
Covalent bond towards itself. In general, the electro negativity of the elements decreases down the
group and increases along the period.
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QUESTIONS ON PERIODIC CLASSIFICATION OF ELEMENTS
Q1. Three elements X,Y and Z forms a Dobereiner’s triad. What will be the atomic mass of Y?.
2. Name the missing element in the triad of Cl and I.
3. What is the limitation of Dobereiner’s triads?
4.’ Properties of elements are a periodic function ofof their atomic masses’ who gave this
statement ?
5.What are the criteria used by Mendeleev in creating his periodic table. Write three limitations of
Mendeleev’s periodic table.
6. A metal M forms an Oxide having the formula M2O3 . It belongs to 3rd period in the modern
periodic table . Write the atomic number and valency of the metal.
7. What are the limitations of Newland’s law of Octave?
8. Which element was named as “Eka-Silicon” in Mendeleev’s Periodic table?.
9. An element ‘X’ belong to group 16 and third period . Name the element. Predict its nature
whether metal or non metal.
10. Two elements X and Y have atomic numbers 12 and 17 respectively. Write the electronic
configuration and valencies of these elements. Write the formula of the compound and the nature
of the bond formed between them? To which period of the Modern periodic table do these two
elements belong?
11. The elements Li, Be, B , C ,N, O ,F and Ne are present in the second period . How many valence
electrons do these elements have? Classify them as metals and non metals.
12. An atom ‘X’ has electronic configuration 2,8,7.
a)What is the atomic number of this element?
b) State whether ‘X’ is a metal or non-metal?
c) What type of ion will be formed by element ‘X’?
d) To which period does the element ‘X’ belong?
13. Why do the elements present in a group have similar chemical properties?
14. Define atomic radius. How does it vary along a period and down a group in the periodic table?
15. The element Li, Be, B, C, N, O belong to the second period. Which element has the largest and
the smallest atom? How does the atomic radius change as you go from left to right in a period?
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16. What is the valency of the element ‘X’ with atomic number 12 and ‘Y’ with atomic number 16?
How does the valency vary in going down the group? Which of the two elements will be metal?
17. The elements Li, Na, K, Rb, and Cs belong to group 1. Name the elements which have the
smallest and the largest atom. How does the atomic size vary on going down a group? Which of
these elements have the maximum metallic character?
18. The elements ‘X’ &’Y’ with atomic number 12&13 respectively form oxides. Write the formulae
of the oxides. Indicate the nature of the oxides formed by these elements?
19. Write the electronic configuration of the first three elements of group 1. How many valence
electrons are present in these three elements? What will be the valency of these elements? What
will be the nature of the oxides formed by these elements?
20. What were the achievements and limitations of Mendeleev’s periodic table?
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VALUE BASED QUESTIONS
STD X CHEMISTRY
Chaper-4. CARBON AND ITS COMPOUNDS
Q-1. Mrs. Anita observed that her cooking utensils are becoming
black in colour and the flame of her gas stove is yellowish in colour
what can be the reason for this sooty flame. How is this problem
harmful for our environment? What steps should be taken to stop this
process.
Q-2. Ethanol is used on a large scale at commercial level this is a
very useful chemical. It is commonly called alcohol and is the active
ingredient of alcoholic drink. But consumption of alcohol also causes
drunkenness and this practice is Socially condemned. As a
responsible student of class –X what steps you would take to
discourage the use of alcohol.
Q-3. You must have seen advertisements stating that some vegetable
oils are healthy. Saturated fatty acids which are said to be harmful for
health. Why vegetable oils are considered healthy then Saturated
fatty acids (ghee)? What precautions you would take in selecting a
cooking oil.
Chapter – 5 PERIODIC CLASSIFICATION OF ELEMENTS
Q-1.. Ria and Rama are students of Class-X. Ria is very much
organized and maintained. The teachers love her. She earns a great
respect in the class where as Rama is un-organised and always faces
a lot of problems in handling life situations.
(i). In your opinion how organization help in daily life?
(ii). How can you relate the above fact with the chapter classification
of elements. How classification of elements help us in studying them
properly?
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Q-2. Adulteration is becoming a very serious problem of our society.
Study reveals that more people die because of food adulteration
rather than hunger. Shopkeepers mix harmful chemicals and things in
food items to earn more profit which may even lead to deaths.
(i). Being a responsible citizen how can you fight against
adulteration?
(ii). Give an example of food adulteration.
(iii) How will you test about the adulteration in this food item?
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CHAPTER No. 4 Carbon and its
compounds HOTS: (High Order Thinking
Skill) Questions with Answers:
1.An organic compound X with a molecular formula C2H6O undergoes
oxidation with in presence of alkaline KMnO4 to form a compound Y. X
on heating in presence of Conc. H2SO4 at 443K gives Z.which on reaction
with H2Oin presence of H2SO4 gives back `X.` `Z` reacts with Br2 (aq)
and decolorizes it. Identify X, Y, & Z.and write the reactions involved.
2.
An organic compound ‘A’ is widely used as a preservative in pickles
and has a molecular formula C2H2O2. This compound reacts with ethanol
to form a sweet smelling compound ‘B.
(i) Identify the compound ‘A’
(ii) Write the chemical equation for its reaction with ethanol to form
compound ‘B’.
(iii) How can we get compound ‘A’ back from ‘B’?
(iv) Name the process and write corresponding chemical equation.
(v) Which gas is produced when compound ‘A’ reacts with washing
soda?
Write the chemical equation.
3.
Hydrocarbon `X` and `Y` having molecular formulae C3H8 and
C3H6 respectively. Both are burnt in different spatula on the bunsen flame.
Indicate the color of the flame produced by `X` and `Y`. Identify `X` and
`Y`. Write the structural formulae.
4.
A compound `X` has molecular formula C4H10. It undergoes
substitution reaction readily than addition reaction. It burns with blue
flame and is present in LPG. Identify `X` and give the balanced equation
for its combustion and substitution reaction with Cl2 in presence of
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