CHEM 2425
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- 1.1. If 50.0 g of benzene, C6H6, at 25.00C absorbs 2.71 kJ of energy in the form of heat, what is the final temperature of the benzene? The specific heat of benzene is 1.72 J/g·0C.
- A.
25.00C
- B.
31.50C
- C.
56.50C
- D.
32.30C
- E.
57.30C
- 2.2. If 495 J is required to change the temperature of 12.7 g of sodium chloride from 75.00C to 135 0C, what is the specific heat of sodium chloride?
- A.
0.866 J/g·0C
- B.
2.60 J/g·0C
- C.
0.650 J/g·0C
- D.
1.15 J/g·0C
- E.
2.83 × 105 J/g·0C
- 3.3. Water has a specific heat of 4.18 J/g · 0C. If 35.0 g of water at 98.8 0C loses 4.94 kJ of heat, what is the final temperature of the water?
- A.
32.00C
- B.
46.20C
- C.
47.20C
- D.
57.20C
- E.
65.0C
- 4.4. When 66.0 g of an unknown metal at 28.50C is placed in 83.0 g H2O at 78.50C, the water temperature decreases to 75.90C. What is the specific heat capacity of the metal? The specific heat capacity of water is 4.184 J/g0C.
- A.
0.055 J/g· 0C
- B.
0.29 J/g · 0C
- C.
0.69 J/g · 0C
- D.
0.18 J/g · 0C
- E.
2.6 J/g · 0C
- 5.5. A coffee-cup calorimeter contains 10.0 g of water at 59.000C. If 3.00 g gold at 15.20 0C is placed in the calorimeter, what is the final temperature of the water in the calorimeter? The specific heat of water is 4.18 J/g ·0C; the specific heat of gold is 0.128 J/g ·0C.
- A.
55.37 C
- B.
58.60 C
- C.
59.40 C
- D.
60.80 C
- E.
64.19 C
- 6.6. When 10.0 g KOH is dissolved in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 25.18 0C to 47.53 0C. What is the enthalpy change per gram of KOH dissolved in the water? Assume that the solution has a specific heat capacity of 4.18 J/g0C.
- A.
–116 J/g
- B.
–934 J/g
- C.
–1.03 × 103 J/g
- D.
–2.19 × 103 J/g
- E.
–1.03 × 104 J/g
- 7.7. 10.0 g of ice at 0.00 0C is mixed with 25.0 g of water at 35.000C in a coffee-cup calorimeter. What is the final temperature of the mixture? The specific heat of water is 4.18 J/g 0C; the heat of fusion of water is 333 J/g.
- A.
0.00 0C
- B.
2.24 0C
- C.
5.22 0C
- D.
25.0 0C
- E.
47.8 0C
- 8.8. All of the following statements are true EXCEPT
- A.
Hess' law states that ΔH for an overall reaction is the sum of the ΔH values for the individual equations.
- B.
The molar enthalpy of formation of a compound is equal to the enthalpy change when one mole of the compound is formed from elements.
- C.
A reaction with a negative enthalpy is exothermic.
- D.
The enthalpy of formation of an element in its most stable state is equal to zero.
- E.
The sum of the enthalpies of formation of the products in a chemical reaction is defined as the enthalpy of reaction.
- 9.9. Determine the heat of reaction for the combustion of ammonia, 4NH3(g) + 7O2(g) → 4NO2(g) + 6H2O(l) using molar enthalpies of formation. NH3(g) –45.9 NO2(g) +33.1 H2O(l) –285.8
- A.
+30.24 kJ
- B.
–206.9 kJ
- C.
–298.6 kJ
- D.
–1398.8 kJ
- E.
–1663.6 kJ
- 10.10. The standard molar enthalpy of formation of NH3(g) is –45.9 kJ/mol. What is the enthalpy change if 9.51 g N2(g) and 1.96 g H2(g) react to produce NH3(g)?
- A.
–10.3 kJ
- B.
–20.7 kJ
- C.
–29.8 kJ
- D.
–43.7 kJ
- E.
–65.6 kJ
- 11.11. For the reaction below relate the rate of disappearance of hydrogen to the rate of formation of ammonia. N2(g) + 3H2(g) → 2NH3(g)
- A.
A: +
- B.
B: 3
- C.
C: 1/2
- D.
D: -1/3
- E.
E: -
- 12.12. The rate of reaction for the formation of carbon monoxide is measured at 1.24 mol/L·hr. What is the rate of formation of carbon monoxide in units of mol/L·s? CH3CHO(g) → CH4(g) + CO(g)
- A.
3.44 × 10-4 mol/L·s
- B.
2.07 × 102 mol/L·s
- C.
1.24 mol/L·s
- D.
74.4 mol/L·s
- E.
4.64 × 103 mol/L·s
- 13.
- A.
–0.360 mol/L·s
- B.
–0.090 mol/L·s
- C.
0.090 mol/L·s
- D.
0.180 mol/L·s
- E.
0.360 mol/L·s
- 14.14. Dinitrogen pentaoxide decomposes to nitrogen dioxide and oxygen according to the following balanced chemical equation and rate expression. 2N2O5(g) → 4NO2(g) + O2(g) rate = k[N2O5] What is the overall reaction order?
- A.
0
- B.
1
- C.
2
- D.
5
- E.
7
- 15.
- A.
Rate = 0.515[A] x [B]
- B.
Rate = 0.515[A]^2 x [B]
- C.
Rate = 0.721[A]^2 x [B]
- D.
Rate = 0.721[A] x [B]^2
- E.
Rate = 0.721[A]^2 x [B]^2
- 16.16. The initial rates method was used to study the reaction below. 2A + B + C → D + E
[A] (mol/L) [B] (mol/L) [C] (mol/L) Δ[D]/Δt (mol/L·s) 0.150 0.250 0.300 1.47 × 106 0.150 0.125 0.300 3.68 × 107 0.150 0.250 0.600 2.94 × 106 0.300 0.125 0.300 7.35 × 107 - A.
Rate = 8.71 × 104[A]2 × [B] × [C]
- B.
Rate = 5.23 × 104[A] × [B]2 × [C]
- C.
Rate = 2.90 × 103[A]2 × [B] × [C]2
- D.
Rate = 8.71 × 104[A] × [B] × [C]2
- 17.17. The rate constant of a first-order decomposition reaction is 0.0147 s–1. If the initial concentration of reactant is 0.178 M, what is the concentration of reactant after 30.0 seconds?
- A.
8.72 × 105 M
- B.
0.0645 M
- C.
0.115 M
- D.
0.0785 M
- E.
0.643 M
- 18.18. The rate constant for the decomposition of cyclobutane is 2.08 × 10-2 s-1 at high temperatures. C4H8(g) → 2C2H4(g) How many seconds are required for an initial concentration of 0.100 M C4H8(g) to decrease to 0.0450 M?
- A.
0.00114 s
- B.
1.07 s
- C.
2.64 s
- D.
38.4 s
- E.
874 s
- 19.
- A.
0.0050 M
- B.
0.051 M
- C.
0.51 M
- D.
0.11 M
- E.
2.0 × 102 M
- 20.20. For the first-order reaction below, the concentration of product B after 24.2 seconds is 0.322 M. If k = 8.75 × 10-2 s-1, what was the initial concentration of A?
A → 2B rate = k[A] - A.
0.0341 M
- B.
0.183 M
- C.
1.34 M
- D.
2.68 M
- E.
29.3 M
- 21.
- A.
2.0 × 10^1 s
- B.
7.8 × 10^1 s
- C.
1.8 × 10^2 s
- D.
1.9 × 10^2 s
- E.
2.2 × 10^2 s
- 22.22. For the first-order reaction below, the initial concentration of A is 0.80 M. What is the half-life of the reaction if the concentration of A decreases to 0.10 M in 54 seconds?
A → B rate = k[A] - A.
18 s
- B.
24 s
- C.
36 s
- D.
48 s
- E.
51 s
- 23.Which of the following statements is/are CORRECT? 1. Product concentrations appear in the numerator of an equilibrium constant expression. 2. A reaction favors the formation of products if K >> 1. 3. Stoichiometric coefficients are used as exponents in an equilibrium constant expression.
- A.
1 only
- B.
2 only
- C.
3 only
- D.
2 and 3
- E.
1, 2, and 3
- 24.
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What is the correct equilibrium constant expression for the following reaction? CO2(g) + 2H2O(g) CH4(g) + 2O2(g) a. b. c. d.- A.
A
- B.
B
- C.
C
- D.
D
- 25.
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25. Write a balanced chemical equation which corresponds to the following equilibrium constant expression.- A.
1/2N2(g) + 3/2H2(g) = NH3(g)
- B.
N2(g) + 3 H2(g) = 2NH3(g)
- C.
2NH3(g) = N2(g) + 3H2(g)
- D.
NH3(g) = 1/2N2(g) + 3/2H2(g)
- E.
2N2(g) + 6H2(g) = 4NH3(g)
- 26.
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Use the equilibrium constants for the following reactions at 700 0C
to determine the equilibrium constant for the following reaction. SO3(g) + NO(g) SO2(g) + NO2(g)2SO2(g) + O2(g) 2SO3(g) K1 = 4.8 2NO(g) + O2(g) 2NO2(g) K2 = 16 - A.
0.30
- B.
0.55
- C.
0.85
- D.
1.8
- E.
3.3
- 27.
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- A.
0.00153
- B.
0.00308
- C.
0.00611
- D.
0.00730
- E.
0.02471
- 28.
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28. For the system CO(g) + H2O(g) CO2(g) + H2(g) K is 1.6 at 900 K. If 0.400 atm CO(g) and 0.400 atm H2O(g) are combined in a sealed flask, what is the equilibrium partial pressure of CO2(g)?- A.
0.22 atm
- B.
0.31 atm
- C.
0.47 atm
- D.
0.47 atm
- E.
0.65 atm
- 29.29. Which of the following may change the ratio of products to reactants in an equilibrium mixture for a chemical reaction involving gaseous species? 1. Increasing the temperature. 2. Adding a catalyst. 3. Adding gaseous reactants.
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1 and 2
- E.
1 and 3
- 30.
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Calcium carbonate decomposes to calcium oxide and carbon dioxide.
The equilibrium constant for this reaction is 9.7 × 1024 at 298 K. What is the equilibrium constant at 575 K? (R = 8.31 J/mol·K)CaCO3(s) CaO(s) + CO2(g) ΔH0 = 179 kJ - A.
7.5 × 10^-16
- B.
1.3 × 10^-8
- C.
1.4 × 10^-38
- D.
1.3 × 10^-15
- E.
1.0 * 10^-23
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