Download Homework,1 Atoms, molecules, and ions

Homework,1 Atoms, molecules, and ions
Student Name………………………………….. Student No. ………………………
1- Naturally occurring neon consists of two isotopes: 20Ne and 22Ne. How many neutrons are
in each isotope ?
a) 20, 22
b) 21, 23
c) 10, 10
d) 11, 13
e) 10, 12
2- An elemental ion has 22 protons, 20 electrons, and 26 neutrons. Which isotope is it?
a) 48Fe
b) 47Fe
c) 48Ti
d) 48Ti2e) 48Ti2+
.
3- What is the name for CuS?
a) copper(II) sulfide
b) copper(I) sulfur
c) copper(I) sulfide
d) copper sulfide
e) copper(II) sulfur
4- Elements belonging to which group of the periodic table form ions with a 2+ charge?
a) alkaline earth metals
b) Halogens
c) Chalcogens
d) alkali metals
5- An element in the lower left corner of the periodic table
a) is either a metal or metalloid.
b) is definitely a metal.
c) is either a metalloid or a nonmetal.
d) is definitely a nonmetal.
e) is definitely a metalloid.
6- Which of the following statements is true for neutral atoms?
a) It is possible for neutral atoms of different elements to have the same number of electrons.
b) The number of neutrons in a neutral atom must always equal the number of protons.
c) The number of neutrons in a neutral atom must always equal the number of electrons.
d) It is possible for neutral atoms of different elements to have the same number of neutrons.
e) It is possible for neutral atoms of different elements to have the same number of protons.
7- Which of the following compounds would you expect to be molecular and not ionic?
a) KCl (potassium chloride, a dietary salt substitute)
b) TiO2 (titanium dioxide, formed in skywriting)
c) ZnS (zinc sulfide, used in photo-sensors)
d) SiC (silicon carbide, an abrasive)
e) CaO (calcium oxide, an acid-neutralizing agent)
8- Which one of the following is named correctly?
a) Ca(HS)2, calcium sulfide
b) HBrO2, bromic acid
c) AlN, aluminum nitride
d) FeO, iron(III) oxide
e) NH4+, ammonia
9- Which of these acids has a name that begins with hydro-?
a) HCl
b) HClO
c) HClO2
d) HClO3
e) HClO4
10- Which of the following compounds is not a possible ionic compound?
a) CsCl
b) SrO
c) GaF3
d) Cs2O
e) NaF2
Homework, 2, Stoichiometry
Student name…………………………………..
Student no………………….
1- Balance the following equation and indicate whether it is a combustion, combination, or
decomposition reaction.
H2O2 + SO2  H2SO4
a) H2O2 + SO2  H2SO4, decomposition reaction
b) 2H2O2 + SO2  H2SO4, decomposition reaction
c) 2H2O2 + SO2  H2SO4, combination reaction
d) H2O2 + SO2 H2SO4, combination reaction
2- Which of the following cannot be an empirical formula?
a) CH
b) CO2
c) NO2
d) C3H6
e) H2N
3- How many atoms are present in 5.54 g F2?
a. 1.76  1023 atoms
c. 0.292 atom
b. 8.78  1022 atoms
d. 3.52  1023 atom
4- A compound contains only carbon, hydrogen and sulfur. When a 4.142 mg sample is
burned completely in oxygen,
5.868 mg of CO2 and 3.603 mg of H2O are formed. What is the empirical formula?
a. CH3S2
b. C2H5S
c. C2H4S
d. C2H6S
5- What is the largest mass of Cl2 that could be prepared from the reaction of 15.0 g of MnO2
(F. Wt. = 87) and 30.0 g of HCl (M. Wt. = 36.5) according to the following equation?
MnO2 + 4HCl  MnCl2 + Cl2 + 2H2O
a. 14.6 g
b. 12.2 g
c. 5.8 g
d. 0.82 g
6- Calculate the mass percent of nitrogen in HNO3.
a) 45.2%
b) 25.0%
c) 22.2%
d) 20.0%
e) none of these
7- You are setting up a reaction between two chemicals that react according to the equation
3 A + 4 B  products.
If you start with 1.00 mole each of both A and B, which chemical will be in excess at the end,
and by how much (assuming the reaction goes to completion)?
a) A is in excess by 0.333 mol.
b) B is in excess by 0.333 mol.
c) B is in excess by 0.250 mol.
d) Neither A nor B is in excess, because the reaction "goes to completion."
e) A is in excess by 0.250 mol.
8- For the reaction Fe(CO)5 + 2PF3 + H2  Fe(CO)2(PF3)2(H)2 + 3CO, how many moles of
CO are produced from a mixture of 5.0 mol Fe(CO)5, 8.0 mol PF3, and 6.0 mol H2?
a) 15 mol
b) 5.0 mol
c) 18 mol
d) 6.0 mol
e) 12 mol
9- What is the percent yield of CaO in the reaction CaCO3  CaO + CO2 if 5.33 g of CaO are
obtained when 10.0 g of CaCO3 are used?
a) 5.60%
b) 53.3%
c) 64.7%
d) 5.33%
e) 95.1%
10- The alcohol in E85 fuel burns according to the following equation:
C2H5OH + 3O2  2CO2 + 3H2O
How many grams of CO2 are produced when 3.00 g of C2H5OH are burned in this way?
a) 6.00 g
b) 88.0 g
c) 0.130 g
d) 5.73 g
e) 2.87 g
11- Consider the reaction C7H8 + 3HNO3  C7H5N3O6 + 3H2O
How many grams of HNO3 are required to react with 10.0 g of C7H8?
a) 20.5 g
b) 6.81 g
c) 30.0 g
d) 2.28 g
Homework,3
Reactions in Aqueous solutions
Student name………………………………………….. Student number………………………
1- Which of the followings are nonelectrolytes in water?
(i) HF
(ii) ethanol, C2H5OH
(iii) C12H22O11
(iv) KClO3
(v) Cu(NO3)2
a) ii and iii ( they are molecular compounds )
b) i, ii, and iii
c) i, iv, and v
d) iii
e) ii
2- Which reactions will not produce a precipitate from aqueous solution?
a) AgNO3 + KI
b) FeSO4 + Ba(OH)2
c) Pb(NO3)2 + Na2CO3
d) ZnCl2 + (NH4)2S
e) NaBr + Al2(SO4)2 (Both AlBr3 and Na2SO4 are soluble.)
3- What volume of 0.125 M H2SO4 is required to neutralize 2.50 g of Ca(OH)2?
a) 0.270 mL
b) 0.135 mL
c) 135 mL
d) 270 mL (The neutralization requires 0.0338 moles of H2SO4.)
4- Based on the activity series, which of the following reactions will occur?
(i)Al(s) + NiCl2(aq)
(ii)Ag(s) + Pb(NO3)2(aq)
(iii)Cr(s) + NiSO4(aq)
a) i only
b) ii only
c) iii only
d) i and ii
e) i and iii (Al is more easily oxidized than Ni, and Cr is more easily oxidized than Ni.)
5- What mass of ethanol, C2H5OH, is required to produce 300. mL of a 0.500 M solution?
a) 46.1 g
b) 23.0 g
c) 6.91 g (There are 0.150 moles of ethanol.)
d) 92.1 g
e) 13.8 g
6- What is the mass of the precipitate formed when 12.0 mL of 0.150 M NaCl is added to
25.00 mL of a 0.0500 M AgNO3 solution?
a) 258 g
b) 0.258 g
c) 179 g
d) 0.179 g (AgCl is the precipitate, and AgNO3 is the limiting reagent.)
e) 36.0 g
7- Indicate the concentration of each ion or molecule present in a 0.25 M CaBr2 solution.
a) 0.25 M Ca2+, 0.25 M Br−
b) 0.25 M Ca2+, 0.50 M Br− (There are two times the moles of Br− compared to Ca2+.)
c) 0.25 M CaBr2
d) 0.50 M Ca2+, 0.50 M Br−
e) 0.50 M Ca2+, 0.25 M Br−
8- What is/are the spectator ion(s) when a BaCl2 solution is combined with an H2SO4 solution?
a) Ba2+(aq), H+(aq)
b) SO42−(aq), H+(aq)
c) Cl−(aq)
d) Cl−(aq), H+(aq) (BaCl2(aq) + H2SO4(aq)  BaSO4(s) + 2HCl(aq))
e) H+(aq)
9- A solution is made by mixing 30.0 mL of 8.00 M HCl, 100 mL of 2.00 M HCl, and enough
water to make 200.0 mL of solution. What is the molarity of HCl in the final solution?
a) 0.455 M
b) 1.00 M
c) 1.20 M
d) 2.20 M (There are 0.240 moles in the first solution and 0.200 moles in the second.)
e) 0.440 M
f) 10.00 M
10- If 5.20 g of a salt are found in 0.180 L of a 0.500 M solution, how many grams would be
present in 0.180 L of a 1.50 M solution?
a) 5.20 g
b) 10.4 g
c) 15.6 g (There is three times more of the salt in the same volume of the more concentrated
solution.)
d) 1.73 g
e) 7.8 g
11- A solution is made of 25.0 mL of 0.250 M nitric acid and 15.0 mL of 0.500 M
hydrochloric acid all diluted to 250. mL. What is the resulting concentration of the hydrogen
ion?
a) 55.0 M
b) 0.0800 M
c) 0.0300 M
d) 0.0500 M
e) 0.0550 M
(Just 0.0.00625 moles of H+ are provided by the HNO3, and 0.00750 moles are provided by
the HCl
Homework, 4 Thermochemistry
Student Name………………………………………..
Student No……………………….
1- When heat is absorbed by the system from the surroundings, the process is said to be
____________, and the sign of q is ___________.
a) endothermic, positive
b) exothermic, positive
c) exothermic, negative
d) endothermic, negative
2- A 2.839-g sample of C2H4O was burned in a bomb calorimeter with a total heat capacity of
16.77 kJ/°C. The temperature of the calorimeter increases from 22.62°C to 26.87°C. What is
the heat of combustion per mole of C2H4O?
a) −61.2 kJ/mol
b) −1.10 x 103 kJ/mol
c) −3.93 kJ/mol
d) −3.14 x 103 kJ/mol
e) −8.90 x 103 kJ/mol
f) −260. kJ/mol
3- The specific heat of lead is 0.13 J/g-K. How many joules of heat would be required to raise
the temperature of 15 g of lead from 22°C to 37°C?
a) 29 J
b) −0.13 J
c) 2.0 J
d) 5.8 x 10−4 J
4- Which of the following changes always results in a negative E?
a) The system absorbs heat and does work.
b) The system absorbs heat and has work done on it.
c) The system gives off heat and does work.
d) The system gives off heat and has work done on it.
5- For a process in which the internal energy does not change, which of the following are
possible?
(i) heat > 0, work < 0
(ii) heat > 0, work > 0
(iii) heat < 0, work < 0
(iv) heat < 0, work > 0
a) ii and iv only
b) i and ii only
c) i and iii only
d) ii and iii only
e) i and iv only
f) iii and iv only
6- The fuel used in spacecraft must contain as much energy per gram of material as possible.
Based on this
consideration only, which of the following fuels is best suited to be a spacecraft fuel?
(a) dimethylhydrazine, (CH3)2NNH2 Hcombustion = −1694 kJ/mol
(b) methanol, CH3OH Hcombustion = −726 kJ/mol
(c) ethanol, C2H5OH Hcombustion = −1371 kJ/mol
(d) octane, C8H18Hcombustion = −5500 kJ/mol
(e) ethylene glycol, C2H6O2 Hcombustion = −1190 kJ/mol
7- Use the H values for equations 1 and 2 to determine the value of H for equation 3.
(1) 2NO  N2 + O2 H = −180. kJ
(2) 2NO + O2  2NO2 H = −112 kJ
(3) N2 + 2O2 2NO2 H = ?
a) −292 kJ
b) 68 kJ
c) −68 kJ
d) 292 kJ
7- From the following enthalpies of reaction,
H2(g) + F2(g)  2HF(g) H = −537 kJ
C(s) + 2F2(g)  CF4(g) H = − 680. kJ
2C(s) + 2H2(g)  C2H4(g) H = +52.3 kJ
calculate H for the reaction of ethylene with F2:
C2H4(g) + 6F2(g)  2CF4(g) + 4HF(g)
a) −1165 kJ
b) +234 kJ
c) −2486 kJ
d) −1269 kJ
e) −2382 kJ
8- Which of the following quantities ( heat, work, enthalpy, internal energy) depend only on
the end points and not on the path followed in a process?
a) heat
b) work
c) enthalpy and internal energy
d) enthalpy
e) internal energy
9- When 0.215 mol NH3 is formed from nitrogen and hydrogen, 9.91 kJ of energy is released
as heat. Assuming constant pressure is maintained, what is the H for this reaction per mole
of NH3 formed?
a) −9.91 kJ
b) 46.1 kJ
c) 9.91 kJ
d) −2.13 kJ
e) −46.1 kJ
10- A volume of 50.0 mL of 0.400 M HBr at 24.35°C is added to 50.0 mL of 0.400 M NaOH,
also at 24.35°C. The final temperature is 27.06°C. Calculate the enthalpy change, H, in kJ
for the following reaction:
HBr(aq) + NaOH(aq)  NaBr(aq) + H2O(l)
(Heat capacity of the system is 0.418 kJ/°C.)
a) −324 kJ
b) −28.4 kJ
c) −56.7 kJ
d) −113 kJ
Homework, 5. Properties of solutions
.................................. ...‫الرقم الجامعي‬
............................................................‫اسم الطالبة‬
I- True or false
1-(
T
) The solubility of gases in water decreases with increasing temperature.
2-(
T
) A mixture of three gases is a solution of gas in gas
3-( T ) The decrease in vapor pressure of a solution, P increases when molality
of non volatile solute increases.
4-( F
5-(
) The ppm concentration is usually used for large concentration solutions.
T ) The hypertonic solution is the more concentrated solution
II- Choose the most correct answer
1- What is the percent CdSO4 by mass in a 1.0 molal aqueous solution (molar mass of CdSO4
= 208.46 g/mol)?
a. 0.001 %
b. 0.10 %
c. 17.2 %
d. 20.8 %
2- When 12.1 g of the sucrose (a nonelectrolyte) are dissolved in exactly 800 g of water, the
solution has a freezing point of - 0.082oC. What is the molar mass of sucrose?
Kf = 1.86oC/m.
a. 426 g/mol
b. 99.2 g/mol
c. 178 g/mol
d. 343 g/mol
3- 0.2 g of non electrolytic solute is dissolved in 20 g of a liquid to elevate the boiling point of
the liquid by 0.180C. What is the molecular weight of solute ? Kb= 4.212oC/m.
a. 117 g/mol
b. 23.4 g/mol
c. 202 g/mol
d. 234 g/mol
4- Which of the following aqueous solutions should have the lowest osmotic pressure?
a. 0.01 M sucrose at 25oC
c. 0.012 M CaCl2 at 25oC
b. 0.008 M NaCl at 25oC
d. 0.01 M sucrose at 50oC
5- The density of a 0.641 M solution of Pb(NO3)2 solution is 1.18 g/cm3? What is the molality
of the solution?
(formula weights of Pb(NO3)2 = 331.2).
a. 0.641
b. 0.662
c. 622
d. 0.0641
6- Which of the following aqueous solutions will have the highest boiling point?
a. 0.10 m Na2SO4
b. 0.20 m glucose
c. 0.10 m NaCl
d. 0.10 m SrSO4
7- How many grams of ethylene glycol ( M Wt. = 62.1 )must be added to 1.0 kg of water to
produce a solution that freeses at –5.0 OC. ( for water, Kf = 1.86 OC/m).
a) 35g
b) 167g
c) 89g
d) 466g
Homework, 6. chemical kinetics
......................................‫الرقم الجامعي‬
.................................................................‫اسم الطالبة‬
1- A first-order reaction has a rate constant of 3.0  10 ─ 3 s
the reaction to be 75% complete is:
a. 95.8 s
b. 201 s
─1
. The time required for
c. 231 s
d. 462 s
2- The reaction: A + 2B  products, was found to follow the rate law: rate =
k[A]2[B].
Predict by what factor the rate of reaction will increase when the concentration
of A is doubled and the concentration of B is tripled, and the temperature
remains constant.
a. 5
b. 6
c. 12
d. 18
3- The activation energy for the reaction 2HI  H2 + I2 is 184 kJ/mol. How many
times greater is the rate constant for this reaction at 520oC than at 500oC?
A. 0.18
b. 0.50
c. 2.0
d. 4.0
4- At 35oC and 70oC the first order rate constants of a reaction are 2.50 x 10-5 and
3.26 x 10-3 s-1 respectively. What is the enthalpy of activation (kJ/mole)?).
a. 117
b. 127
c. 122
d. 130
5- What is the kinetic rate law for the following data:
Exp #
1
2
3
4
a. rate = k[A][B]
[A]
1.5
1.5
3.0
3.0
[B]
1.5
3.0
4.5
3.0
b. rate = k[A]2[B]
Rate
0.2
0.8
3.6
1.6
c. rate = k[A][B]2
d. rate = k[A]
6 A certain first-order reaction A  B is 25% complete in 42 min at 25oC. What is
the half-life of the reaction?
a. 21 min
b. 42 min
c. 84 min
d. 101 min
7- The data in the table below were obtained for the reaction:
2 ClO2(aq) + 2 OH-(aq)  ClO3-(aq) + ClO2-(aq) + H2O(1)
Exp. No. [CO2](M) [OH](M)
1
0.060
0.030
2
0.020
0.030
3
0.020
0.090
Rate(M/s)
0.0248
0.00276
0.00828
What is the magnitude of the rate constant for the reaction?
a. 4.6
b. 230
c. 115
d. 713
Homework, 7. chemical equilibrium
................................... .‫الرقم الجامعي‬
.....................................................‫ ة‬/‫اسم الطالب‬
1- For the following reactions the equilibrium constants are defined:
A + 2B  C K1
C  D + E K2
Then for the reaction
A + 2B  D + E Kc
the equilibrium constant must be equal to:
a.Kc = K1 + K2
b. Kc = K1/K2
c. Kc = K1 - K2
d. Kc = K1 ·K2
2- Phosgene, COCl2, a poisonous gas, decomposes according to the equation:
COCl2(g)  CO(g) + Cl2(g)
If Kc = 0.083 at 900oC, what is Kp for this reaction?
a. 0.125
b. 6.1
c. 8.0
d. 0.16
3- For the following reaction at equilibrium in a reaction vessel, which one of the changes
below would cause the Br2 concentration to decrease?
2NOBr(g)  2NO(g) + Br2(g) ΔHorxn = 30 kJ
a decrease the container volume
c. Increase the temperature.
b. remove some NO
d. add more NOBr
4- The equilibrium constant for the following reaction is 0.28 at 900oC. A system at
equilibrium has
[H2S] = 0.100 M, [H2] = 0.100 and [CH4] = 1.40 x 10-4 M. What is the [CS2]?
CS2(g) + 4 H2(g)  CH4(g) + 2 H2S(g)
a. 0.25
b. 0.15
c. 0.10
d. 0.050
5- Consider the reactions below. In which cases is product formation favored by increased
temperature?
1) CO(g) + 3 H2(g)  CH4(g) + H2O(g)
Ho = -206.2 kJ
2) CO2(g) + C(s)  2 CO(g)
Ho = 172.5 kJ
3) H2(g) + I2(g)  2 HI(g)
Ho = -9.4 kJ
4) 3 O2(g)  2 O3(g)
Ho = 285 kJ
a. 1, 3
b. 2, 4
c. 1,4
d. 2, 3
Homework, 8. Acid-base equilibra
................................... .‫الرقم الجامعي‬
..................................................‫ة‬/ ‫اسم الطالب‬
1- What is the OH ─ ion concentration in 5.2  10
a. 1.9  10
─ 11
M
b. 1.0  10
─ 7
M
─ 4
M HNO3?
c. 5.2  10
─ 4
M
d. zero
2- A 0.10 M HF solution is 8.4% ionized. Calculate the H+ ion concentration.
a. 8.4  10
─ 3
b. 0.084 M
c. 0.12 M
d. 0.84 M
3- Acid strength decreases in the series HNO3 > HF > HC2H3O2 . Which of the following is
the strongest base?
a. NO3─
b. C2H3O2─
c. F ─
d. all the same
4- Hydrosulfuric acid (H2S) has K1 = 1.1 x 10-7 and K2 = 1.0 x 10-13. What is the H+ ion
concentration of
a 0.10 M solution of H2S?
a. 1.0 x 10-4
b. 1.1 x 10-7
c. 3.3 x 10-5
d. 3.3 x 10-4
5- What is the ionization constant of HA if the H+ ion concentration of a 0.390 M solution is
4.52 x 10-5 M?
a. 5.24 x 10-9
b. 7.94 x 10-10
c. 4.52 x 10-4
d. 1.02 x 10-9
6- Consider the following salts. Which one(s) when dissolved in water will produce a basic
solution?
1) NaNO3, 2) CH3COONa, 3) Na2CO3
a. 2 and 3
b. only 3
c. 1 and 2
d. only 2
7- What is the conjugate acid of methylamine, CH3NH2?
a. CH3NH-
b. CH3NH3+
c. CH3NH2+
d. CH3NH+
8- Which one of the following responses is true with regard to a 0.1 M solution of a strong
acid HA?
a. [H+] > [A ─ ]
c. [H+] < [A ─ ]
b. the pH = 1.0
d. the pH > 1.0
9- Calculate the pH of a 0.20 M HA solution. (Ka for HA = 7.2  10 ─ 4 )
a. 1.9
b. 1.6
c. 4.1
10- What is the pH of a 0.1 M solution of a base that has Kb = 1 x 10-5
a. 11.0
b. 3.0
c. 8.5
d. 3.1
d. 9.5
11- Which of the following salts will produce a basic solution when dissolved in water?
a. KClO4
b. NH4NO3
c. Li2CO3
d. Na2SO4
Homework, 9. Additional aspects on Acid-base equilibria
................................... .‫ الرقم الجامعي‬..........................
.........................‫اسم الطالبة‬
1- Calculate the pH of a buffer solution which contains 0.25 M benzoic acid (C6H5CO2H) and
0.15 M sodium benzoate (NaC6H5CO2). Given Ka = 6.5  10 ─ 5.
a. 4.83
b. 3.97
c. 3.40
d. 4.41
2- 50.00 mL of 0.10 M HNO2 (nitrous acid) was titrated with 0.10 M KOH solution. After
25.00 mL of KOH solution was added, the pH in the titration flask will be:
Given Ka = 4.5  10 ─ 4
a. 2.17
b. 3.35
3- The Ksp value for PbCl2 is 2.4  10
a. 2.4  10
c. 7.7  10
─4
c. 2.41
d. 8.9
. What is the molar solubility of PbCl2?
b. 6.2  10
d. 3.9  10
─4
mol/L
─3
mol/L
─2
─2
mol/L
mol/L
4- The solubility of BaCrO4 (formula weight = 253.3) is 3.5 x10-3 g/L. What is the Ksp?
a. 3.0 x 10-8
b. 1.9 x 10-10
c. 1.4 x 10-5
d. 1.9 x 10-5
5- What is the pH of a buffer solution that is 0.211 M in lactic acid and 0.111 M in sodium
lactate? The Ka of lactic acid is 1.4 × 10 ─ 4
a. 5.48
b. 3.57
c. 4.13
d. 10.43