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
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
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) /
B) / Kc =
C) / Kc =
D) / Kc =
E) / Kc =
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
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.
Answer Key
1. / C2. / A
3. / B
4. / D
5. / D
6. / B
7. / A
8. / C
9. / A
10. / B
11. / B
12. / C
13. / D
14. / B
15. / D
16. / A
17. / C
18. / E
19. / B
20. / B
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