CHEM 1412 Test 2 Review
Name: __________________________ Date: _____________
1. Which one of these salts will form an acidic solution upon dissolving in water?
A) LiBr
B) NaF
C) NH4Br
D) KOH
E) NaCN
2. Calculate the concentration of chromate ion (CrO42–) in a 0.450 M solution of chromic
acid (H2CrO4). [For chromic acid, Ka1 = 0.18, Ka2 = 3.2 X 10–7.]
A) 3.2 X 10–7 M
B) 1.5 X 10–6 M
C) 0.081 M
D) 1.1 X 10–6 M
E) 0.21 M
3. Predict the direction in which the equilibrium will lie for the reaction
H3PO4(aq) + HSO4–(aq)  H2PO4–(aq) + H2SO4(aq).
Ka1(H3PO4) = 7.5 X 10–3; Ka(H2SO4) = very large
A) to the right
B) to the left
C) in the middle
4. The pOH of a solution is 10.40. Calculate the hydrogen ion concentration in the
solution.
A) 4.0 X 10–11 M
B) 3.6 M
C) 4.0 X 10–10 M
D) 2.5 X 10–4 M
E) 1.8 X 10–4 M
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5. Arrange the acids HBr, H2Se, and H3As in order of increasing acid strength.
A) HBr < H2Se < H3As
B) HBr < H3As < H2Se
C) H2Se < H3As < HBr
D) H3As < H2Se < HBr
E) H3As < HBr < H2Se
6. Identify the conjugate base of HCO3– in the reaction
CO32– + HSO4– HCO3– + SO42–
A) HSO4–
B) CO32–
C) OH–
D) H3O+
E) SO42–
7. Identify the conjugate base of HClO3 in the reaction
ClO3– + HSO4– HClO3 + SO42–
A) ClO3–
B) HSO4–
C) OH–
D) H3O+
E) SO42–
8. Identify the conjugate acid of HCO3– in the reaction
HCO3– + HPO42–  H2CO3 + PO43–
A) H2O
B) HCO3–
C) H2CO3
D) PO43–
E) HPO42–
9. Due to a highway accident, 150 L of concentrated hydrochloric acid (12.0 M) is
released into a lake containing 5.0 X 105 m3 of water. If the pH of this lake was 7.0
prior to the accident, what is the pH of the lake following the accident?
A) 5.44
B) 8.56
C) 8.44
D) 5.56
E) 2.44
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10. The equilibrium constant for the reaction
C6H5COOH(aq) + CH3COO–(aq)  C6H5COO–(aq) + CH3COOH(aq)
is 3.6 at 25°C. If Ka for CH3COOH is 1.8 X 10–5, what is the acid dissociation constant for
C6H5COOH?
A) 5.0 X 10–6
B) 6.5 X 10–5
C) 2.3 X 10–4
D) 8.3 X 10–5
E) 5.6 X 10–6
11. The reaction 2NO(g)  N2(g) + O2(g) is exothermic, ΔHºrxn = –180 kJ/mol. Which one of
these statements is true?
A) Kp at 1,000 K is less than Kp at 2,000 K.
B) Kp at 1,000 K is larger than Kp at 2,000 K.
C) The Kp's at 1000 K and 2000 K are the same.
D) Kp depends on total pressure as well as temperature.
12. The equilibrium between carbon dioxide gas and carbonic acid is very important in
biology and environmental science.
CO2(aq) + H2O(l)  H2CO3(aq)
Which one of the following is the correct equilibrium constant expression (Kc) for this
reaction?
A)
 H 2CO3 
Kc 
 CO 2  H 2O 
B)
[CO2 ][H2O]
Kc = [H2CO3 ]
C)
[H2CO3 ]
K = [CO2 ]
c
D)
[CO2 ]
Kc = [H2CO3 ]
1
E)
K = [H2CO3 ]
c
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13. Carbon tetrachloride reacts at high temperatures with oxygen to produce two toxic
gases, phosgene and chlorine.
CCl4(g) + 1/2O2(g)  COCl2(g) + Cl2(g), Kc = 4.4 X 109 at 1,000 K
Calculate Kc for the reaction 2CCl4(g) + O2(g)  2COCl2(g) + 2Cl2(g).
A) 4.4 X 109
B) 8.8 X 109
C) 1.9 X 1010
D) 1.9 X 1019
E) 2.3 X 10–10
14. On analysis, an equilibrium mixture for the reaction 2H2S(g)  2H2(g) + S2(g) was found
to contain 1.0 mol H2S, 4.0 mol H2, and 0.80 mol S2 in a 4.0 L vessel. Calculate the
equilibrium constant, Kc, for this reaction.
A) 1.6
B) 3.2
C) 12.8
D) 0.64
E) 0.8
15. 1.25 moles of NOCl were placed in a 2.50 L reaction chamber at 427ºC. After
equilibrium was reached, 1.10 moles of NOCl remained. Calculate the equilibrium
constant, Kc, for the reaction 2NOCl(g)  2NO(g) + Cl2(g).
A) 3.0 X 10–4
B) 1.8 X 103
C) 1.4 X 10–3
D) 5.6 X 10–4
E) 4.1 X 10–3
16. If one starts with pure NO2(g) at a pressure of 0.500 atm, the total pressure inside the
reaction vessel when 2NO2(g)  2NO(g) + O2(g) reaches equilibrium is 0.674 atm.
Calculate the equilibrium partial pressure of NO2.
A) 0.152 atm
B) 0.174 atm
C) 0.200 atm
D) 0.326 atm
E) The total pressure cannot be calculated because Kp is not given
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17. Hydrogen iodide decomposes according to the equation 2HI(g)  H2(g) + I2(g), for
which Kc = 0.0156 at 400ºC. 0.550 mol HI was injected into a 2.00 L reaction vessel at
400ºC. Calculate the concentration of H2 at equilibrium.
A) 0.275 M
B) 0.138 M
C) 0.0275 M
D) 0.0550 M
E) 0.220 M
18. If the reaction 2H2S(g)  2H2(g) + S2(g) is carried out at 1065°C, Kp = 0.0120. Starting
from pure H2S introduced into an evacuated vessel at 1065°C, what will the total
pressure in the vessel be at equilibrium if the equilibrated mixture contains 0.300
atm of H2(g)?
A) 1.06 atm
B) 1.36 atm
C) 2.39 atm
D) 4.20 atm
E) 1.51 atm
19. Solid ammonium hydrogen sulfide is introduced into a 2.00-L flask, and the flask is
sealed. If this solid decomposes according to the equation
NH4HS(s) - NH3(g) + H2S(g), Kp = 0.108 at 25°C,
what is the minimum mass of ammonium hydrogen sulfide that must be present in the
flask initially if equilibrium is to be established at 25°C?
A) 0.917 g
B) 1.37 g
C) 2.74 g
D) 0.581 g
E) 0.452 g
20. The equilibrium constants for the chemical reaction
N2(g) + O2(g)  2NO(g) are KP = 1.1 X 10–3 and 3.6 X 10–3 at 2,200 K and 2,500 K,
respectively. Which one of these statements is true?
A) The reaction is exothermic, ΔHº < 0.
B) The partial pressure of NO(g) is less at 2,200 K than at 2,500 K.
C) KP is less than Kc by a factor of (RT).
D) The total pressure at 2,200 K is the same as at 2,500 K.
E) Higher total pressure shifts the equilibrium to the left.
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Answer Key
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C
A
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D
D
B
A
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B
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B
D
A
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E
B
B
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