CHEM 1411
PRACTICE EXAM II (Chapters 4, 5, 6): 25 questions.
Multiple Choices: Select one best answer. Q1-9: Chapter 4; Q10-18: Chapter 5; Q19-25: Chap 6
Page numbers include both 9th and 10th editions of the textbooks.
1. Which of the following is a weak electrolyte?
(a) barium hydroxide solution
(b) argon gas
(c) ammonia solution
(d) water
(e) liquid aluminum chloride
Hint: 10th ed. p. 122; 9th ed. p.p. 120-121. Weak electrolytes include molecular compounds that are
weak acids and weak bases. Strong electrolytes include ionic compounds and molecular compounds
that are strong acids.
Nonelectrolytes include all molecular compounds except strong acids, weak acids and weak bases.
2. Which of the following is wrong concerning a net-ionic equation?
(a) S2-(aq) + Zn2+(aq)  ZnS(s)
(b) 2NaOH(aq) + MgSO4(aq) Mg(OH)2(s) + Na2SO4(aq)
(c) SO42-(aq) + Pb2+(aq) PbSO4(s)
(d) CO32-(aq) + 2H+(aq)H2O(l) + CO2(g)
2+
2+
(e) Fe(s) +Ni (aq)  Fe + Ni(s)
Hint: 10th ed. p.p. 126-127. Example 4.2; 9th ed. p.p. 124-126 & Examples 4.1 & 4.2. Check with the
solubility table for the products, which must be solids (s), liquids (l) or gases (g). For (e): see Fig 4.16.
3. Which of the following is a Brǿnsted acid?
(a) HSO4(b) CH3COO(c) SO42(d) ClO4(e) NO3th
th
Hint: 10 ed. p. 130; 9 ed. p. 128. Example 4.3. Definition. Brǿnsted acids must contain available
(releasable) hydrogen ions while the Brǿnsted bases must be able to accept hydrogen ions. To obtain
Bronsted acid, simply add H+; to obtain Bronsted base, simply subtract H+.
4. Which of the following underlined atoms contains the oxidation number as -1?
(a) Cs2O
(b) CaC2
(c) SO42(d) PtCl42(e) NaO2
Hint: 10th ed. p.p. 136-139; 9th ed. p.p. 134-137. Memorize the rules. Example 4.5.
5. Which of the following redox reactions will occur according to activity series?
(a) Cu(s) + 2HCl(aq)  CuCl2(aq) + H2(g)
(b) 2Ag(s) + 2H2O(l)  AgOH(s) + H2(g)
(c) Mg(s) + CuSO4(aq)  MgSO4(aq) + Cu(s)
(d) Pt(s) + FeSO4(aq)  PtSO4(aq) + Fe(s)
(e) 2Al(s) + 3Ca(NO3)2(aq)  2Al((NO3)3(aq) + 3Ca(s)
Hint: Activity table: 10th ed. Fig 4.16, p. 143; 9th ed. Fig. 4.16, p. 139. The one on the top of the Table
is more reactive then the one at the bottom. So in order to have a reaction, the metal on top must be in
the neutral atomic form and the one below must be in the compound or ionic form.
6. How many grams of KOH are present in 35.0 mL of a 5.50 M solution?
(a) 5.5
(b) 10.8
(c) 15.7
(d) 17.8
(e) 21.3
Hint: 10th ed. p.p. 147-148, Example 4.6; 9th ed. p.p. 142-146. Example 4.6.
7. What is the final concentration (in M) of a solution when water is added to 25.0 mL of a 0.866 M
KNO3 solution until the volume of the solution is exactly 500.0 mL?
(a) 0.0252
(b) 0.0368
(c) 0.0117
(d) 0.0534
(e) 0.0433
Hint: 10th ed. p.p. 149-151 Similar to Example 4.8; 9th ed. p.p. 146-148. Similar to the reverse question
of Example 4.8.
8. What is the concentration (in M) of the final solution when a 46.2 mL, 0.568 M Ca(NO 3)2 solution
is mixed with 80.5 mL of 1.396 M Ca(NO3)2 solution?
(a) 0.568
(b) 1.09
(c) 0.953
(d) 1.545
(e) 1.874
Hint: 10th ed. p.p. 149-151; 9th ed. p. 146-148. p. 160: 4.74. Mixing solutions is diluting solution. New
concentration = mole of solute/ total volume of solutions. Thus, M = (0.568x46.2+1.396 x
80.5)/(46.2+80.5) = 1.09.
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9. What volume (in mL) of a 0.500 M HCl solution is needed to neutralize 10.0 mL of a 0.2000 M
Ba(OH)2 solution?
(a) 8.00
(b) 4.00
(c) 2.00
(d) 1.00
(e) 0.50
Hint: 10th ed. p.p. 153-156 Example 4.11 ; 9th ed. p.p. 150-153. Solution stoichioimetry. Example 4.11.
Short-cut formula of acid-base neutralization: ia x Ma x Va = ib x Mb x Vb where a refers to acid and b
refers to base. ia refers to number of H in the chemical formula of acid and i b refers to the number of
OH in the chemical formula of base.
10. What volume (in L) does a sample of air occupy at 6.6 atm when 1.2 atm, 3.8 L of air is
compressed?
(a) 0.34
(b) 0.57
(c) 0.69
(d) 0.77
(e) 0.86
Hint: Boyle’s law. 10th ed. p.p. 179-182 Equation (5.2); 9th ed. p.p. 175-178. Equation (5.2).
11. What is the final temperature (in K), under constant-pressure condition, when a sample of
hydrogen gas initially at 88oC and 9.6 L is cooled until its finial volume is 3.4 L?
(a) 31
(b) 68
(c) 94
(d) 130
(e) 260
Hint: Charles’s Law. 10th ed. p.p. 183-184 Equation (5.4); 9th ed. p.p. 178-180. Equation (5.4).
12. What is the volume (in L) of 88.4 g of carbon dioxide gas at STP?
(a) 45.1
(b) 53.7
(c) 62.1
(d) 74.6
(e) 83.2
Hint: Ideal gas law. Equation (5.8): PV = nRT. 10th ed. p.p. 185-187 Examples 5.3 & 5.4; 9th ed. p.p.
181-182. Equation (5.8). Example 5.3.
Application: A gas evolved during the fermentation of glucose (wine making) has a volume of
0.78 L at 20.1oC and 1.00 atm. What was the volume (L) of this gas at the fermentation
temperature of 36.5oC and 2.00 atm pressure?
(a) 0.41 (b) 0.82
(c) 1.43
(d) 2.67
(e) 3.54
Hint: Combined gas law. p. 184 equation (5.10).
13. What is the molar mass (g/mol) of 7.10 grams of gas whose volume is 5.40 L at 741 torr and 40 oC?
(a) 35.0
(b) 70.3
(c) 86.2
(d) 94.6
(e) 102.3
Hint: 10th ed. p.p. 192-194 Examples 5.9 & 5.10; 9th ed. p. 187. Equation (5.12). Example 5.9.
Application: What is the density of HBr gas in grams per liter at 733 mmHg and 46 oC?
(a) 0.54
(b) 1.36
(c) 2.24
(d) 2.97
(e) 3.57
Hint: 10th ed. p.p. 190-191 Example 5.8; 9th ed. p. 186. Equation (5.11). Example 5.8.
14. A compound has the empirical formula as SF4. At 20 oC, 0.100 gram of the gaseous compound
occupies a volume of 22.1 mL and exerts a pressure of 1.02 atm. What is the molecular formula of the
gas?
(a) SF4
(b) SF6
(c) S2F10
(d) S4F16
(e) S5F20
Hint: 10th ed. p.p. 193-194 Example 5.10; 9th ed. p. 211 (5.50) or p. 187. Equation (5.12). Example 5.9.
15. The combustion process for methane, major component of natural gas, is
CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(l)
If 15.0 moles of methane are reacted, what is the volume of carbon dioxide (in L) produced at 23.0 oC
and 0.985 atm?
(a) 370
(b) 430
(c) 510
(d) 630
(e) 720
Hint: Gas stoichiometry: 10th ed. p.p. 194-196 Examples 5.12 & 5.13; 9th ed. p.p. 190-192. Example
5.11. This question is taken from p. 211 (5.52).
16. In alcohol fermentation, yeast converts glucose to ethanol and carbon dioxide:
2
C6H12O6(s)  2 C2H5OH(l)) + 2 CO2(g)
If 5.97 g of glucose are reacted and 1.44 L of carbon dioxide gas are collected at 293 K and 0.984 atm,
what is the precent yield of the reaction?
(a) 88.9 %
(b) 76.3%
(c) 65.9%
(d) 56.2%
(e) 47.6%
Hint: Gas stoichiometry: 10th ed. p.p. 194-196. This question is taken from p. 217 (5.54); 9th ed. p.p.
190-192. This question is taken from p. 212 (5.54).
17. What is the total pressure (in atm) of the mixture when a 2.5-L flask at 15 oC contains a mixture if
nitrogen, helium, and neon gases at partial pressure of 0.32 atm for nitrogen, 0.15 atm for helium, and
0.42 atm for neon?
(a) 0.49
(b) 0.51
(c) 0.64
(d) 0.73
(e) 0.89
Hint: Total pressure is the sum of all partial pressures of component gases.
10th ed. p.p. 196-199. This question is taken from p. 218 (5.64 (a)); 9 th ed. p.p. 192-195.This question
is taken from p. 212 (5.64 (a)).
18. Nickel forms a gaseous compound of the formula Ni(CO) x. What is the value of x given the fact
that under the same conditions of temperature and pressure, methane (CH 4) effuses 3.3 times faster
than the compound?
(a) 1
(b) 2
(c) 3
(d) 4
(e) 5
Hint: 10th ed. p.p. 208-209 Example 5.17. This question is taken from p. 219 (5.84); 9 th ed. p.p. 203204. Example 5.17. This question is taken from p. 213 (5.84).
19. What is the change in energy (J) of the gas when a gas expends and does P-V work on the
surroundings equal to 325 J and at the same time absorbs 127 J of heat from the surroundings?
(a) -198
(b) + 198
(c) + 157
(d) -157
(e) + 452
Hint: 10th ed. p. 238: Example 6.2; 9th ed. p. 232: Example 6.2.
20. Consider the reaction below:
2CH3OH(l) + 3O2(g)  4H2O(l) + 2CO2(g) ∆H = -1452.8 kJ
What is the value of ∆H for the reaction of
8H2O(l) + 4CO2(g)  4CH3OH (l) + 6O2 (g)?
(a) +1458.2
(b) -1458.2
(c) 3.46
(d) -2905.6
(e) +2905.6
Hint: 10th ed. p.p. 241-243; 9th ed. p. 236: Guidelines or p. 249: Examle 6.9: concepts to use in multiple
or reversing equation..
21. What is the heat absorbed (in kJ) when 250 grams of water is heated from 22 oC to 98oC? The
specific heat of water is 4.18 J/g.K (or 4.18 J/g. oC)
(a) 79
(b) 88
(c) 97
(d) 102
(e) 137
Hint: 10th ed. p.p. 245-246 Example 6.5; 9th ed. p. 240: Example 6.5.
22. A sheet of gold weighing 10.0 g and at a temperature of 18.0 oC is placed flat on a sheet of iron
weighing 20.0 g and at a temperature of 55.6 oC. What is the final temperature (oC) of the combined
metals? Assume that no heat is lost to the surroundings. The specific heat of iron and gold are o.444
and 0.129 J/g.oC , respectively. (Hint: the heat gained by the gold must be equal to the heat lost by the
iron.)
(a) 50.7
(b) 63.1
(c) 72.4
(d) 47.2
(e) 36.8
Hint: Hear absorbed by the colder object gold = - heat released by the hotter object iron.
10th ed. p. 249: Example 6.7 ; 9th ed. p. 243: Example 6.7. p. 256: problem 6.36.
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23. Calculate the heat of combustion (kJ) for the following reaction:
2H2S(g) + 3O2(g)  2H2O(l) + 2SO2(g)
The standard enthalpies of formation for H2S(g), H2O(l), SO2(g) and O2(g) are
-20.15, -285.8, -296.4 and 0.0, respectively.
(a) +1124
(b) -1124
(c) +562 (d) -562
(e) +281
Hint: The Direct Method: 10th ed. 252-254 Equation (6.18), Example 6.10; 9th ed. p. 246: Equation
6.17 or 6.18, p. 247: in-text example, and p. 250: Example 6.10.
24. From the following data,
C(graphite) + O2(g)  CO2(g)
H2(g) + 1/2O2(g)  H2O(l)
2C2H6(g) + 7O2(g)  4CO2(g) + 6H2O(l)
∆H = -393.5 kJ
∆H = -285.8 kJ
∆H = -3119.6 kJ
Calculate the enthalpy change (kJ) for the reaction
2C(graphite) + 3H2(g)  C2H6(g)
(a) -84.6 (b) -42.3 (c) +84.6
(d) +42.3
(e) -67.2
Hint: The Indirect Method (Hess’ Law). 10th ed. p.p. 255-258 Example 6.9; 9th ed. p.p. 248-250:
in-text example and Example 6.9.
Terms used and procedures:
(a) Identity refers to either react or product;
(b) Quantity refers to coefficient;
(c) Given reactions: Two or more reactions with ∆H given;
(d) Target reaction/equation: The one that is asked; Must use it as reference. Any given reaction
that is different from it must be reversed or multiplied by a number (whole or fraction);
(e) Resultant reaction/equation: The one that was obtained by adding the given reactions that have
been manipulated.
(f) If the resultant reaction is identical to the target reaction, you are solving it correctly. So add all
the given reactions that have been manipulated together to get the ∆H.
25. Calculate the standard enthalpy change (kJ) for the reaction
2Al(s) + Fe2O3(s)  2Fe(s) + Al2O3(s)
Given that
2Al(s) + 3/2O2(g)  Al2O3(s)
2Fe(s) + 3/2O2(g)  Fe2O3(s)
∆H = -1669.8 kJ
∆H = -822.2 kJ
(a) -637.1
(b) -847.6
(c) -984.6
(d) -1120.3
(e) +847.6
Hint: 10th ed. p.p. 255-258 Example 6.9; 9th ed. p.p. 248-250: in-text example and Example 6.9.
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