CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
TUTORIAL 1 (INTRODUCTORY CONCEPTS)
1. Calculate the number of moles in 0.197 g As2O3.
(a) 9.96 x 10-4 mol (b) 5.05 x 10-3 mol (c) 39.0 mol (d) 198 mol (e) 1.00 x 103 mol
2. What is the mass of 8.04 x 10-3 mol I2?
(a) 3.17 x 10-5 g (b) 0.490 g (c) 0.980 g (d) 1.02 g (e) 2.04 g
3. How many hydrogen atoms are in 1.0 g of CH4?
(a) 6.2 x 10-2 atoms (b) 2.5 x 10-1 atoms (c) 3.8 x 1022 atoms (d) 1.5 x 1023 atoms
(e) 3.9 x 1025 atoms
4. If 1.00 g of an unknown molecular compound contains 8.35 x 1021 molecules, what is the
molar mass?
(a) 44.0 g/mol (b) 66.4 g/mol (c) 72.1 g/mol (d) 98.1 g/mol (e) 132 g/mol
5. What is the mass percent of iodine in calcium iodide?
(a) 13.64% (b) 24.00% (c) 66.67% (d) 76.00% (e) 86.36%
6. What is the mass percent of each element in sulphuric acid?
(a) 2.055% H, 32.69% S, 65.25% O (b) 1.028% H, 32.69% S, 66.28% O
(c) 28.57% H, 14.29% S, 57.17% O (d) 1.028% H, 33.72% S, 65.25% O
(e) 2.016% H, 32.07% S, 65.91% O
7. Nitrogen and oxygen form an extensive series of oxides with the general formula NxOy.
What is the empirical formula for an oxide that contains 36.85% by mass nitrogen?
(a) N2O (b) NO (c) NO2 (d) N2O3 (e) N2O5
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
8. A molecule is found to contain 64.27% by mass C, 7.191% by mass H, and 28.54% by
mass O. What is the empirical formula for this molecule?
(a) C2H6O (b) C3H4O (c) C3H8O2 (d) C4H6O2 (e) C4H8O3
9. An ionic compound has a formula MCl2. The mass of 0.3011 mol of the compound is 62.69
grams. What is the identity of the metal?
(a) Ni (b) Cu (c) Sn (d) Hg (e) Ba
10. What is the molar mass of potassium nitrate?
(a) 39.10 g/mol (b) 53.11 g/mol (c) 85.11 g/mol (d) 101.1 g/mol (e) 163.1 g/mol
11. The empirical formula of acetic acid is CH2O. If its molar mass is 60 g/mol, what is the
molecular formula of acetic acid?
12. Isoprene is a liquid compound that can be polymerized to form synthetic rubber. It is
composed of 88.17% C and 11.83% H. Its molar mass is 68.11 g/mol. What are its
empirical and molecular formula?
13. Camphor is found in “camphor wood” much prized for its wonderful colour. It is composed
of 78.90% C and 10.59% H. The remainder is oxygen. What is its empirical formula?
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
TUTORIAL 2 (CHEMICAL REACTIONS) [STOICHIOMETRY]
1. When ethanol undergoes complete combustion, the products are carbon dioxide and
water.
C2H5OH(l) + O2(g) → CO2(g) + H2O(l)
What are the respective coefficients when the equation is balanced with the smallest
whole numbers?
(a) 1, 1, 1, 1 (b) 1, 2, 1, 3 (c) 2, 3, 4, 6 (d) 1, 3, 2, 3 (e) 2, 7, 4, 6
2. Iron rusts according to the following equation:
Fe(s) + O2(g) → Fe2O3
What are the respective coefficients when the equation is balanced?
(a) 1, 1, 1 (b) 1, 3, 1 (c) 2, 3, 1 (d) 3, 3, 2 (e) 4, 3, 2
3. Aluminium reacts with oxygen to produce aluminium oxide.
4Al(s) + 3O2 → 2Al2O3(s)
If 4.0 moles of Al react with excess O2, how many moles of Al2O3 can be formed?
(a) 2.0 mol (b) 4.0 mol (c) 6.0 mol (d) 7.0 mol (e) 8.0 mol
4. The complete combustion of 0.20 moles of pentane, C5H12, will
(a) Consume 0.20 mol O2 and produce 0.20 mol CO2
(b) Consume 1.0 mol O2 and produce 1.0 mol CO2
(c) Consume 1.6 mol O2 and produce 1.0 mol CO2
(d) Consume 2.0 mol O2 and produce 1.0 mol CO2
(e) Consume 2.0 mol O2 and produce 1.6 mol CO2
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
5. Iron reacts with hydrochloric acid to produce iron (II) chloride and hydrogen gas.
Fe(s) + 2 HCl(aq) → FeCl2(aq) + H2(g)
What mass of H2(g) is produced from the reaction of 5.2 g Fe (s) with excess hydrochloric
acid?
(a) 0.094 g (b) 0.19 g (c) 5.2 g (d) 6.8 g (e) 1.4 x 102 g
6. What mass of water is produced by the complete combustion of 6.21 g of hexane, C6H14?
(a) 0.186 g (b) 1.30 g (c) 9.09 g (d) 43.5 g (e) 208 g
7. Under certain conditions the formation of ammonia from nitrogen and hydrogen has a
9.82% yield. Under these conditions, what mass of NH3 will be produced from the reaction
15.0 g N2 with 2.00 g H2?
N2(g) + 3H2(g) → 2NH3(g)
(a) 1.11 g (b) 1.67 g (c) 1.79 g (d) 3.32 g (e) 11.3 g
8. Aspirin is produced by the reaction of salicylic acid (M = 138.1 g/mol) and acetic anhydride
(M = 102.1 g/mol).
C7H6O3(s) + C4H6O3(l) → C9H8O4(s) + C2H4O2(l)
If 2.04 g of C9H8O4(M = 180.2 g/mol) is produced from the reaction of 3.03 g C7H6O3 and
4.01 g C4H6O3, what is the percent yield?
(a) 28.8% (b) 29.0% (c) 50.9% (d) 51.6% (e) 67.3%
9. How many litres of 0.2805 M C6H12O6(aq) contain 1.000 g of C6H12O6?
(a) 0.001557 L (b) 0.01979 L (c) 0.2805 L (d) 3.565 L (e) 50.5 L
10. Iron reacts with hydrochloric acid.
Fe(s) + 2HCl(aq) → FeCl(aq) + H2(g)
What volume of 2.55 M HCl (aq) will react with 35.0 g Fe(s)?
(a) 0.246 L (b) 0.492 L (c) 1.60 L (d) 3.20 L (e) 27.5 L
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
11. The thermite reaction produces iron metal and aluminium oxide from a mixture of
powdered aluminium metal and iron (III) oxide.
Fe2O3(s) + 2 Al (s) → 2 Fe(l) + Al2O3(s)
A mixture of 50.0 g each of Fe2O3 and Al is used.
(a) Which is the limiting reactant?
(b) What mass of iron metal can be produced?
12. Aluminium carbide, Al4C3, reacts with water to produce methane.
Al4C3(s) + 12H2O(l) → 4Al(OH)3(s) + 3CH4(g)
If 125 g of aluminium carbide is composed, what is the theoretical yield of methane? If
only 13.6 g of methane is obtained, what is the percent yield of this gas?
13. A 0.523 g sample of the unknown compound CxHy was burned in air to give 1.612 g of
CO2 and 0.7425 g H2O. A separate experiment gave a molar mass for CxHy of 114 g/mol.
Determine the empirical and molecular formulas for the hydrocarbon.
14. An experiment in your laboratory requires 250 ml of a 0.0200 M solution of AgNO 3. You
are given solid AgNO3, distilled water, and 250 ml volumetric flask. Describe how to make
up the required solution.
15. If you combine 75.0 ml of 0.350 M HCl and an excess of Na2CO3, what mass of CO2, in
grams, is produced?
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
TUTORIAL 3 (REDOX REACTIONS)
1. Which species is oxidized in the reaction below?
I-(aq) + ClO-(aq) → IO-(aq) + Cl-(aq)
(a) I- (b) H2O (c) Cl- (d) IO- (e) ClO2. What is the oxidation number of iodine in potassium periodate, KIO4?
(a) -1 (b) 0 (c) +3 (d) +5 (e) +7
3. What is the oxidation number of sulphur dichloride, SCl2?
(a) -2 (b) 0 (c) +2 (d) +4 (e) +6
4. What is the oxidation number of each atom in sulphurous acid, H2SO3?
(a) H = +1, S = -2, O = -2 (b) H = 0, S = +6, O = -2 (c) H = 0, S =0, O = 0
(d) H = +1, S = +4, O = -2 (b) H = -1, S = +8, O = -2
5. What is the oxidation number of each atom in sodium phosphate, Na3PO4?
(a) Na = +1, P = -3, O = -2 (b) Na = +1, P = +5, O = -2 (c) Na = +1, P = -3, O = +2
(d) Na = -1, P = +5, O = -2 (e) Na = 0, P = 0, O = 0
6. Which of the following elements generally acts as an oxidizing agent?
(a) Cl2 (b) H2 (c) F- (d) C (e) Na
7. Which of the following chemical equations show oxidation-reduction reactions?
(i) Mg(s) + I2(aq) → MgI2(s)
(ii) Pb(ClO4)2(aq) + 2KI(aq) → PbI2(s) + 2NaClO4(aq)
(iii) Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO(g)
(a) (i) only (b) (ii) only (c) (i) and (ii) (d) (i) and (iii) (e) (ii) and (iii)
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
8. Which molecule in the reaction below is the reducing agent?
2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g)
(a) C2H6 (b) O2 (c) H2O (d) CO2 (e) None
9. Which species in the reaction below undergoes reduction?
2Na(s) + 2H2O(aq) → 2Na+(aq) + 2OH-(aq) + H2(g)
(a) Na (b) H2O (c) Na+ (d) OH- (e) H2
10. Determine the oxidation number of the indicated element in each ion or molecule:
(a) Iron in Fe2O3 (b) Sulphur in H2SO4 (c) Carbon in CO32- (d) Nitrogen in NO2+
11. Balance the following redox reactions:
(a) As + HNO3 + H2O → H3AsO4 + NO
(b) NaOH + S → Na2S2O3 + Na2S + H2O
(c) FeCl3 + H2O + SO2 → FeCl2 + H2SO4 + HCl
(d) KMnO4 + KNO2 + H2SO4 → K2SO4 + MnSO4 + KNO3 + H2O
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
TUTORIAL 4 (CHEMICAL BONDING)
1. Which combination of atoms is most likely to produce a compound with covalent bonds?
(a) Na and Cl (b) Al and O (c) S and Br (d) Pb and F (e) K and I
2. Which of the following statements is/are correct?
(i) Ionic bonds form when one or more valence electrons are transferred from one atom
to another.
(ii) Covalent bonds involve sharing of electrons between atoms.
(iii) In most covalently bonded compounds, electrons are shared equally between the
atoms.
(a) i only (b) ii only (c) iii only (d) i and ii (e) i, ii and iii
3. How many lone pairs of electrons are assigned to the carbon atom in carbon monoxide?
(a) 0 (b) 1 (c) 2 (d) 3 (e) 4
4. Which of the following molecules or ions are isoelectronic: SO2, CO2, NO2+, ClO2-?
(a) SO2 and CO2 (b) SO2 and NO2+ (c) CO2 and ClO2- (d) CO2 and NO2+
(e) SO2, NO2+ and ClO25. If two or more species have the same number of electrons, resulting in similar Lewis
structures, they are said to be __________.
(a) Isoelectronic (b) Resonant structures (c) Ionic (d) Neutral (e) Covalent
6. The central atom in SCl2 is surrounded by
(a) One single bond, one double bond, and no lone pairs of electrons
(b) One single bond, one double bond, and one lone pairs of electrons
(c) Two single bonds and no lone pairs of electrons
(d) Two single bonds and two lone pairs of electrons
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
(e) Two double bonds and no lone pairs of electrons
7. Which of the following elements is able to form a molecular structure that exceeds the
octet rule?
(a) Ne (b) B (c) O (d) F (e) I
8. When both of the electrons in a molecular bond originate from the same atom, the bond
is called a(n)
(a) Sigma bond (b) Coordinate covalent bond (c) Pi bond (d) Metallic bond
(e) Ionic bond
9. Which of the following molecules or ions does not have one or more resonance structures?
(a) O3 (b) SCN- (c) CO32- (d) H2CO (e) SO2
10. A selenium atom has __________ valence electrons.
(a) 2 (b) 6 (c) 16 (d) 28 (e) 34
11. Draw the Lewis electron dot structures of CO, NH4+, NO+ and SO42-.
12. Draw resonance structures for the bicarbonate ion, HCO313. Identify the hybridization of Sulphur in SF3+ and SO42-
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
TUTORIAL 6 (THE GASEOUS STATE)
1. Gaseous mixtures __________.
(a) can only contain molecules (b) are all heterogeneous (c) can only contain isolated
atoms (d) are all homogeneous (e) must contain both isolated atoms and molecules
2. Which of the following statements about gases is false?
(a) Gases are highly compressible.
(b) Distances between molecules of gas are very large compared to bond distances within
molecules.
(c) Non-reacting gas mixtures are homogeneous.
(d) Gases expand spontaneously to fill the container they are placed in.
(e) All gases are colorless and odorless at room temperature.
3. One significant difference between gases and liquids is that __________.
(a) a gas is made up of molecules
(b) a gas assumes the volume of its container
(c) a gas may consist of both elements and compounds
(d) gases are always mixtures
(e) All of the above answers are correct.
4. Which of the following equations shows an incorrect relationship between pressures given
in terms of different units?
(a) 1.20 atm = 122 kPa (b) 152 mm Hg = 2.03 × 104Pa (c) 0.760 atm = 578 mm Hg
(d) 1.0 torr = 2.00 mm Hg (e) 1.00 atm = 760 torr
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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5. The pressure exerted by a column of liquid is equal to the product of the height of the
column times the gravitational constant times the density of the liquid, P = ghd. How high
a column of methanol (d = 0.79 g/mL) would be supported by a pressure that supports a
713 mm column of mercury (d = 13.6 g/mL)?
(a) 713 mm (b) 41 mm (c) 1.2 × 104 mm (d) 9.7 × 103 mm (e) 17 mm
6. The pressure exerted by a column of liquid is equal to the product of the height of the
column times the gravitational constant times the density of the liquid, P = ghd. How high
a column of water (d = 1.0 g/mL) would be supported by a pressure that supports a 713
mm column of mercury (d = 13.6 g/mL)?
(a) 14 mm (b) 52 mm (c) 713 mm (d) 1.2 × 104 mm (e) 9.7 × 103 mm
7. In ideal gas equation calculations, expressing pressure in Pascals (Pa), necessitates the
use of the gas constant, R, equal to __________.
(a) 0.08206 atm L mol-1K-1 (b) 8.314 J mol-1K-1 (c) 62.36 L torr mol-1K-1
(d) 1.987 cal mol-1K-1 (e) none of the above
8. A pressure of 1.00 atm is the same as a pressure of _________ of mmHg.
(a) 33.0 (b) 193 (c) 760.0 (d) 101 (e) 29.92
9. A gas at a pressure of 10.0 Pa exerts a force of _________ N on an area of 5.5 m2.
(a) 5.5 (b) 0.55 (c) 55 (d) 1.8 (e) 18
10. The first person to investigate the relationship between the pressure of a gas and its
volume was __________.
(a) Amadeo Avogadro (b) Lord Kelvin (c) Jacques Charles (d) Robert Boyle
(e) Joseph Louis Gay-Lussac
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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11. Of the following, __________ is a correct statement of Boyle's law.
(a) PV = constant
P
(b) V = constant
V
(c) P = constant
V
(d) T = constant
n
(e) P = constant
12. "Isothermal" means __________.
(a) at constant pressure (b) at constant temperature (c) at variable temperature and
pressure conditions (d) at ideal temperature and pressure conditions
(e) that
H rxn = 0
13. Of the following, __________ is a valid statement of Charles' law.
P
(a) T = constant
V
(b) T = constant
(c) PV = constant
(d) V = constant × n
(e) V = constant × P
14. The volume of an ideal gas is zero at __________.
(a) 0 °C (b) -45 °F (c) -273 K (d) -363 K (e) -273 °C
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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15. Of the following, only __________ is impossible for an ideal gas.
V1 V2
=
T
T2
1
(a)
(b) V1T1 = V2T2
V1 T1
=
V
T2
2
(c)
V2 =
(d)
T2
V1
T1
V1 T1
= 0
V
T2
2
(e)
16. The molar volume of a gas at STP is __________ L.
(a) 0.08206 (b) 62.36 (c) 1.00 (d) 22.4 (e) 14.7
17. How many moles of gas are there in a 45.0 L container at 25.0°C and 500.0 mm Hg?
(a) 0.630 (b) 6.11 (c) 18.4 (d) 1.21 (e) 207
18. The volume of 1.20 mol of gas at 61.3 kPa and 25.0°C is __________ L.
(a) 135 (b) 48.5 (c) 52.4 (d) 108 (e) 55.7
19. A piece of solid carbon dioxide with a mass of 5.50 g is placed in a 10.0 L vessel that
already contains air at 94.0 kPa and 24°C. After the carbon dioxide has totally vaporized,
what is the partial pressure of carbon dioxide and the total pressure in the container at
24°C?
(a) 30.86 kPa and 124.4 kPa (b) 13.10 kPa and 26.20 kPa (c) 13.10 kPa and 124.4 kPa
(d) 30.86 kPa and 13.10 kPa (e) 50.45 kPa and 100.80 kPa
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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20. Ni(CO)4 can be made by reacting finely divided nickel with gaseous CO. If you have CO in
a 1.5 L flask at a pressure of 418 mmHg at 25°C, along with 0.450 g of Ni powder, what
is the theoretical yield of Ni(CO)4?
21. Hydrazine reacts with O2 according to the following equation:
N2H4(g) + O2(g) → N2(g) + 2H2O(l)
Assume the oxygen gas needed for the reaction is in a 450000 ml tank at 23°C. What
must the oxygen pressure be in the tank to have enough oxygen to consume 1.00 kg of
hydrazine completely?
22. Halothane, C2HBrClF3, is a non-flammable, non-explosive, and non-irritating gas
that is commonly used as an inhalation anaesthetic. The total pressure of a mixture
of 15.0 g halothane vapour and 23.5 g oxygen gas is 855 mmHg. What is the partial
pressure of each gas?
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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2020
TUTORIAL 7 (CHEMICAL KINETICS)
1. Of the following, all are valid units for a reaction rate except __________.
(a) mol/L (b) M/s (c) mol/hr (d) g/s (e) mol/L-hr
2. Nitrogen dioxide decomposes to nitric oxide and oxygen via the reaction:
2NO2 → 2NO + O2
In a particular experiment at 300 °C, [NO2] drops from 0.0100 to 0.00650 M in 100 s. The
rate of disappearance of NO2 for this period is __________ M/s.
(a) 0.35 (b) 3.5 × 10-3 (c) 3.5 × 10-5 (d) 7.0 × 10-3 (e) 1.8 × 10-3
3. At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and
oxygen:
2N2O5(g) → 4NO2(g) + O2(g)
When the rate of formation of O2 is 2.2 × 10-4 M/s, the rate of decomposition of N2O5 is
__________ M/s.
(a) 1.1 × 10-4 (b) 2.2 × 10-4 (c) 2.8 × 10-4 (d) 4.4 × 10-4 (e) 5.5 × 10-4
4. Which one of the following is not a valid expression for the rate of the reaction below?
4NH3 + 7O2 → 4NO2 + 6H2O

(a)
1 Δ  O2 
7 Δt
1 Δ  NO2 
Δt
(b) 4
1 Δ  H 2O
Δt
(c) 6

(d)
1 Δ  NH3 
4
Δt
(e) All of the above are valid expressions of the reaction rate.
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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5. Of the units below, __________ are appropriate for a first-order reaction rate constant.
(a) M s-1 (b) s-1 (c) mol/L (d) M-1 s-1 (e) L mol-1 s-1
6. The rate law of a reaction is rate = k[D][X]. The units of the rate constant are __________.
(a) mol L-1s-1 (b) L mol-1s-1 (c) mol2 L-2s-1 (d) mol L-1s-2 (e) L2 mol -2s-1
7. The data in the table below were obtained for the reaction:
A + B → P
The rate law for this reaction is rate = __________.
(a) k[A][B] (b) k[P] (c) k[A]2[B] (d) k[A]2[B]2 (e) k[A]2
8. The magnitude of the rate constant in question 7 is __________.
(a) 38.0 (b) 0.278 (c) 13.2 (d) 42.0 (e) 2.21
9. The data in the table below were obtained for the reaction:
2ClO2(aq) + 2OH-(aq) → ClO3-(aq) + ClO2-(aq) + H2O (l)
10. What is the order of the reaction in question 9, with respect to ClO2?
(a) 1 (b) 0 (c) 2 (d) 3 (e) 4
11. What is the order of the reaction in question 9, with respect to OH-?
(a) 0 (b) 1 (c) 2 (d) 3 (e) 4
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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12. What is the overall order of the reaction in question 9?
(a) 4 (b) 0 (c) 1 (d) 2 (e) 3
13. What is the magnitude of the rate constant for the reaction in question 9?
(a) 1.15 × 104 (b) 4.6 (c) 230 (d) 115 (e) 713
14. The rate law for a reaction is
rate = k [A][B]2
Which one of the following statements is false?
(a) The reaction is first order in A. (b) The reaction is second order in B.
(c) The reaction is second order overall. (d) k is the reaction rate constant
(e) If [B] is doubled, the reaction rate will increase by a factor of 4.
15. Under constant conditions, the half-life of a first-order reaction __________.
(a) is the time necessary for the reactant concentration to drop to half its original value
(b) is constant (c) can be calculated from the reaction rate constant
(d) does not depend on the initial reactant concentration (e) All of the above are correct.
16. The rate constant of a first-order process that has a half-life of 225 s is _________ s-1.
(a) 0.693 (b) 3.08 × 10-3 (c) 1.25 (d) 12.5 (e) 4.44 × 10-3
17. The rate constant of a first-order process that has a half-life of 3.50 min is ________ s-1.
(a) 0.693 (b) 1.65 × 10-2 (c) 1.98 (d) 0.198 (e) 3.30 × 10-3
18. One difference between first- and second-order reactions is that __________.
(a) the half-life of a first-order reaction does not depend on [A]0; the half-life of a secondorder reaction does depend on [A]0
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
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(b) the rate of both first-order and second-order reactions do not depend on reactant
concentrations
(c) the rate of a first-order reaction depends on reactant concentrations; the rate of a
second-order reaction does not depend on reactant concentrations
(d) a first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed
(e) None of the above are true.
19. As the temperature of a reaction is increased, the rate of the reaction increases because the
__________.
(a) reactant molecules collide less frequently
(b) reactant molecules collide more frequently and with greater energy per collision
(c) activation energy is lowered
(d) reactant molecules collide less frequently and with greater energy per collision
(e) reactant molecules collide more frequently with less energy per collision
20. The rate of a reaction depends on __________.
(a) collision frequency (b) collision energy (c) collision orientation (d) all of the above
(e) none of the above
21. The gas-phase decomposition of SO2Cl2 is first order in SO2Cl2:
SO2Cl2(g) → SO2(g) + Cl2(g)
(i) At 600 K, the half-life for this process is 2.3 × 105 s. What is the rate constant at this
temperature?
(ii) At 320°C, the rate constant is 2.2 × 10-5 s-1. What is the half-life at 593 K?
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FIRST SEMESTER
2020
22. The decomposition of hydrogen peroxide at 298 K follows the mechanism as below;
H2O2(aq) + I-(aq) → H2O(l) + IO-(aq)
(slow)
IO-(aq) + H2O2 (aq) → H2O(l) + O2(g) + I-(aq)
(Fast)
(i) What is the overall reaction?
(ii) What is the rate law predicted by the reaction mechanism?
(iii) Is there a reaction intermediate? If so, what is it?
(iv) Is there a catalyst? If so, what is it?
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
TUTORIAL 8 (THERMOCHEMISTRY)
1. At what velocity (m/s) must a 20.0 g object be moving in order to possess a kinetic energy
of 1.00 J?
(a) 1.00 (b) 100 × 102 (c) 10.0 (d) 1.00 × 103 (e) 50.0
2. Objects can possess energy as __________.
(i) endothermic energy (ii) potential energy (iii) kinetic energy
(a) i only (b) ii only (c) iii only (d) i and iii (e) ii and iii
3. The internal energy of a system is always increased by __________.
(a) adding heat to the system
(b) having the system do work on the surroundings
(c) withdrawing heat from the system
(d) adding heat to the system and having the system do work on the surroundings
(e) a volume compression
4. The internal energy of a system __________.
(a) is the sum of the kinetic energy of all of its components
(b) is the sum of the rotational, vibrational, and translational energies of all of its
components
(c) refers only to the energies of the nuclei of the atoms of the component molecules
(d) is the sum of the potential and kinetic energies of the components
(e) none of the above
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
5. Which one of the following conditions would always result in an increase in the internal
energy of a system?
(a) The system loses heat and does work on the surroundings.
(b) The system gains heat and does work on the surroundings.
(c) The system loses heat and has work done on it by the surroundings.
(d) The system gains heat and has work done on it by the surroundings.
(e) None of the above is correct.
6. The value of ΔE for a system that performs 111 kJ of work on its surroundings and gains
89 kJ of heat is __________ kJ.
(a) -111 (b) -200 (c) 200 (d) -22 (e) 22
7. The value of ΔE for a system that performs 13 kJ of work on its surroundings and loses 9
kJ of heat is __________ kJ.
(a) 22 (b) -22 (c) -4 (d) 4 (e) -13
8. When a system __________, ΔE is always negative.
(a) absorbs heat and does work (b) gives off heat and does work
(c) absorbs heat and has work done on it (d) gives off heat and has work done on it
(e) none of the above is always negative.
9. Which one of the following is an endothermic process?
(a) ice melting (b) water freezing (c) boiling soup
(d) Hydrochloric acid and barium hydroxide are mixed at 25 °C:
increases.
(e) Both a and c
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the temperature
CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
10. Which one of the following is an exothermic process?
(a) ice melting (b) water evaporating (c) boiling soup (d) condensation of water vapor
(e) Ammonium thiocyanate and barium hydroxide are mixed at 25 °C: the temperature
drops.
11. Of the following, which one is a state function?
(a) H (b) q (c) w (d) heat (e) none of the above
12. Which of the following is a statement of the first law of thermodynamics?
(a) Ek = (1/2) mv2 (b) A negative ΔH corresponds to an exothermic process.
(c) ΔE = Efinal – Einitial (d) Energy lost by the system must be gained by the surroundings.
(e) 1 cal = 4.184 J (exactly)
13. The internal energy can be increased by __________.
(i) transferring heat from the surroundings to the system
(ii) transferring heat from the system to the surroundings
(iii) doing work on the system
(a) i only (b) ii only (c) iii only (d) i and iii (e) ii and iii
14. A __________ ΔH corresponds to an __________ process.
(a) negative, endothermic (b) negative, exothermic (c) positive, exothermic
(d) zero, exothermic (e) zero, endothermic
15. A __________ ΔH corresponds to an __________ process.
(a) negative, endothermic (b) positive, exothermic (c) positive, endothermic
(d) zero, exothermic (e) zero, endothermic
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
16. ΔH for an endothermic process is __________ while ΔH for an exothermic process is
__________.
(a) zero, positive (b) zero, negative (c) positive, zero (d) negative, positive
(e) positive, negative
17. For a given process at constant pressure, ΔH is negative. This means that the process
is __________.
(a) Endothermic (b) equithermic (c) exothermic (d) a state function (e) energy
18. Which one of the following statements is true?
(a) Enthalpy is an intensive property.
(b) The enthalpy change for a reaction is independent of the state of the reactants and
products.
(c) Enthalpy is a state function.
(d) H is the value of q measured under conditions of constant volume.
(e) The enthalpy change of a reaction is the reciprocal of the ΔH of the reverse reaction.
19. Which of the following statements is false?
(a) Internal energy is a state function.
(b) Enthalpy is an intensive property.
(c) The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to the
enthalpy change for the reverse reaction.
(d) The enthalpy change for a reaction depends on the state of the reactants and products.
(e) The enthalpy of a reaction is equal to the heat of the reaction.
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
20. A chemical reaction that absorbs heat from the surroundings is said to be __________
and has a __________ ΔH at constant pressure.
(a) endothermic, positive (b) endothermic, negative (c) exothermic, negative
(d) exothermic, positive (e) exothermic, neutral
21. Sulfur, S8, burns in air to produce sulfur dioxide. The reaction evolves 9.31 kJ of heat per
gram of sulfur at constant pressure. Write the thermochemical equation for this reaction.
22. Suppose that a heat sink at 71.3 °C is dropped into a Styrofoam cup containing 100.0 g
of water at 25.0 °C. The temperature of water rises to 27.4 °C. What is the heat capacity
of the sink, in J/ °C?
23. What is the heat of vaporization of methanol, CH3OH, at standard conditions?
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
TUTORIAL 9 (THERMODYNAMICS AND EQUILIBRIUM)
1. The first law of thermodynamics can be given as __________.
(a) ΔE = q + w
(b) For any nonspontaneous process, the entropy of the universe increases.
(c) for any spontaneous process, the entropy of the universe increases
(d) the entropy of a pure crystalline substance at absolute zero is zero
(e) ΔS = qrev/T at constant temperature
2. A reaction that is spontaneous as written __________.
(a) is very rapid
(b) will proceed without outside intervention
(c) is also spontaneous in the reverse direction
(d) has an equilibrium position that lies far to the left
(e) is very slow
3. Of the following, only __________ is not a state function.
(a) S (b) H (c) q (d) E (e) T
4. When a system is at equilibrium, __________.
(a) the reverse process is spontaneous but the forward process is not
(b) the forward and the reverse processes are both spontaneous
(c) the forward process is spontaneous but the reverse process is not
(d) the process is not spontaneous in either direction
(e) both forward and reverse processes have stopped
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2020
CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
5. A reversible process is one that __________.
(a) can be reversed with no net change in either system or surroundings
(b) happens spontaneously
(c) is spontaneous in both directions
(d) must be carried out at low temperature
(e) must be carried out at high temperature
6. Which of the following statements is true?
(a) Processes that are spontaneous in one direction are spontaneous in the opposite
direction.
(b) Processes are spontaneous because they occur at an observable rate.
(c) Spontaneity can depend on the temperature.
(d) All of the statements are true.
(e) Both a and b are true statements.
7. The thermodynamic quantity that expresses the degree of disorder in a system is
__________.
(a) enthalpy (b) internal energy (c) bond energy (d) entropy (e) heat flow
8. For an isothermal process, ΔS = __________.
(a) q (b) qrev/T (c) qrev (d) Tqrev (e) q + w
9. Which one of the following is always positive when a spontaneous process occurs?
(a) ΔSsystem (b) ΔSsurroundings (c) ΔSuniverse (d) ΔHuniverse (e) ΔHsurroundings
10. The entropy of the universe is __________.
(a) Constant (b) continually decreasing (c) continually increasing (d) zero
(e) the same as the energy, E
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
11. Which of the following statements is false?
(a) The change in entropy in a system depends on the initial and final states of the system
and the path taken from one state to the other.
(b) Any irreversible process results in an overall increase in entropy.
(c) The total entropy of the universe increases in any spontaneous process.
(d) Entropy increases with the number of microstates of the system.
(e) Entropy decreases with the number of nanostates of the system.
12. Consider a pure crystalline solid that is heated from absolute zero to a temperature above
the boiling point of the liquid. Which of the following processes produces the greatest
increase in the entropy of the substance?
(a) melting the solid (b) heating the liquid (c) heating the gas (d) heating the solid
(e) vaporizing the liquid
13. ΔS is positive for the reaction __________.
(a) 2H2(g) + O2(g) → 2H2O(g)
(b) 2NO2(g) → N2O4(g)
(c) CO2(g) → CO2(s)
(d) BaF2(s) → Ba2+(aq) + 2F-(aq)
(e) 2Hg(l) + O2(g) → 2HgO(s)
14. ΔS is positive for the reaction __________.
(a) 2NO(g) + O2(g) → 2NO2(g)
(b) 2N2(g) + 3H2(g) → 2NH3(g)
(c) C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
(d) Mg(s) + Cl2(g) → MgCl2(s)
(e) C2H4(g) + H2(g) → C2H6(g)
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
15. Which reaction produces a decrease in the entropy of the system?
(a) CaCO3(s) → CaO(s) + CO2(g)
(b) 2C(s) + O2(g) → 2CO(g)
(c) CO2(s) → CO2(g)
(d) 2H2(g) + O2(g) → 2H2O(l)
(e) H2O(l) → H2O(g)
16. For an isothermal process, the entropy change of the surroundings is given by the
equation:
(a) ΔS = qsys T (b) ΔS = -qsys T (c) ΔS = q lnT (d) ΔS = -q lnT (e) ΔS = -qsys/T
17. A reaction that is not spontaneous at low temperature can become spontaneous at high
temperature if ΔH is __________ and ΔS is __________.
(a) +, + (b) -, - (c) +, - (d) -, + (e) +, 0
18. With thermodynamics, one cannot determine __________.
(a) the speed of a reaction (b) the direction of a spontaneous reaction
(c) the extent of a reaction (d) the value of the equilibrium constant
(e) the temperature at which a reaction will be spontaneous
19. The value of ΔS° for the catalytic hydrogenation of acetylene to ethane,
C2H2(g) + 2H2(g) → C2H6(g)
is __________ J/K∙ mol.
(a) -76.0 (b) +440.9 (c) -232.5 (d) +232.5 (e) +28.7
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CHE 1140/5 and CHE 1145/5 TUTORIAL PROBLEMS
FIRST SEMESTER
2020
20. The value of ΔS° for the formation of POCl3 from its constituent elements,
P2(g) + O2(g) + 3Cl2(g) → 2POCl3(g)
is __________ J/K∙ mol.
(a) -442.0 (b) +771.0 (c) -321.0 (d) -771.0 (e) +321.0
21. The normal boiling point of ethanol, C2H5OH, is 78.3ºC and its molar enthalpy of
vaporization is ∆Hvap = 38.56 kJ/mol. What is the entropy change of the system (in joules
per kelvin) when 68.3 g of C2H5OH(g) at 1 bar condenses to liquid at the normal boiling
point?
22. Calculate the value of the thermodynamic equilibrium constant at 25°C for the reaction;
N2O4 (g) → 2NO2 (g)
23. Consider the following reaction for the formation of methane from carbon and hydrogen
at 298 K:
C (graphite) + 2H2 (g) → CH4 (g)
Calculate ΔG° at 298 K, utilizing values of ΔHf° and S°. Under standard conditions is the
reaction spontaneous at 298 K?
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