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Chapter 6 Review
(84 points)
(3 points) 1. Two gases, A(g) and B(g), are confined in a cylinder-and-piston arrangement. Substances A
and B react to form a solid product:
A(g) + B(g) → C(s)
As the reaction occurs, the system loses 1150.0J of heat to the surroundings. The piston moves downward
as the gases react to form the solid. As the volume of the gas decreases under the constant pressure of the
atmosphere, the surroundings do 480.0J of work on the system. Determine the change in the internal
energy of the system.
(3 points) 2. Calculate the change in the internal energy of the system for a process in which the system
absorbs 140.0J of heat from the surroundings and does 85.0J of work on the surroundings.
3. Calculate ∆E, and determine whether the process is endothermic or exothermic for the following cases:
(3 points) a. A system absorbs 85.0kJ of heat from its surroundings while doing 29.0kJ of work on the
surroundings.
(3 points) b. q = 1.50kJ and w = -657.0J
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(3 points) c. The system releases 57.5kJ of heat while doing 13.5kJ of work on the surroundings.
4. At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat
KClO3:
2 KClO3 (s) → 2 KCl (s) + 3 O2 (g)
∆H = -89.4 kJ
For this reaction, calculate ∆H for the formation of
(3 points) a. 0.855 mol of O2
(3 points) b. 10.75g of KCl
(3 points) 5a. Determine the amount of heat needed to warm 250.0g of water from 22.00C to 98.00C. The
specific heat of water is 4.18 J/g0C.
(3 points) 5b. Determine the molar heat capacity of water.
(3 points) 6a. Large beds of rocks are used in some solar heated homes to store heat. Assume that the
specific heat of the rocks is 0.82 J/g0C. Calculate the quantity of heat absorbed by 50.0kg of rocks if their
temperature increases by 12.00C.
(3 points) 6b. Calculate the temperature change these rocks would undergo if they emitted 450.0kJ of heat.
(3 points) 7. The specific heat of iron metal is 0.450 J/g0C. Determine the amount of heat necessary to
raise the temperature of 1.05 kg block of iron from 25.0 0C to 88.50C.
(3 points) 8. When a 9.55g sample of sodium hydroxide dissolves in 100.0g of water in a coffee cup
calorimeter, the temperature rises from 23.6 0C to 47.40C. Calculate ∆H, in kJ, for the solution process.
Assume the specific heat of the solution is the same as that for water.
NaOH (s) → Na+ (aq) + OH- (aq)
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(3 points) 9. When a student mixes 50.0 mL of 1.0M HCl and 50.0 mL of 1.0M NaOH in a coffee cup
calorimeter, the temperature of the resultant solution increases from 21.0 0C to 27.50C. Calculate the
enthalpy change for the reaction in kJ/mol HCl, assuming that the calorimeter loses only a negligible
quantity of heat, that the total volume of the solution is 100.0 mL, that its density is 1.00 g/mL, and that its
specific heat is 4.18 J/g0C.
HCl (aq) + NaOH (aq) → H2O (l) + NaCl (aq)
10. A 1.800 g sample of phenol (C6H5OH) was burned in a bomb calorimeter whose total heat capacity is
11.66 kJ/0C. The temperature of the calorimeter plus contents increased from 21.36 0C to 26.370C.
(3 points) (a). Write a balanced chemical equation for the bomb calorimeter reaction.
(3 points) (b). Determine the heat of combustion per gram of phenol.
(3 points) 11. Under constant volume conditions the heat of combustion of glucose (C6H12O6) is 15.57
kJ/g. A 2.500g sample of glucose is burned in a bomb calorimeter. The temperature of the calorimeter
increased from 20.550C to 23.250C. Determine the total heat capacity of the calorimeter.
12. Under constant volume conditions, the heat of combustion of benzoic acid (HC7H5O2) is 26.38 kJ/g. A
1.640 g sample of benzoic acid is burned in a bomb calorimeter. The temperature of the calorimeter
increases from 22.250C to 27.200C.
(3 points) (a) Determine the total heat capacity of the calorimeter.
(3 points) (b) A 1.320g sample of a new organic substance is combusted in the same calorimeter. The
temperature of the calorimeter increases from 22.14 0C to 26.820C. Determine the heat of combustion per
gram of the new substance.
(3 points) 13. Calculate the enthalpy change for the reaction
P4O6 (s) + 2 O2 (g) → P4O10 (s)
Given the following enthalpies of reaction:
P4 (s) + 3 O2 (g) → P4O6 (s)
∆H = -1640.1 kJ
P4 (s) + 5 O2 (g) → P4O10 (s)
∆H = -2940.1 kJ
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(3 points) 14. Calculate the heat of reaction for
3 H2 (g) + O3 (g) → 3 H2O (g)
Given the following enthalpies of reaction:
2 H2 (g) + O2 (g) → 2 H2O (g)
∆H = -483.6 kJ
3 O2 (g) → 2 O3 (g)
∆H = 284.6 kJ
(3 points) 15. From the enthalpies of reaction
H2 (g) + F2 (g) → 2 HF (g)
∆H = -537.0 kJ
C (s) + 2 F2 (g) → CF4 (g)
∆H = -680.0 kJ
2 C (s) + 2 H2 (g) → C2H4 (g)
∆H = 52.3 kJ
Calculate ∆H for the reaction of ethylene with F2
C2H4 (g) + 6 F2 (g) → 2 CF4 (g) + 4 HF (g)
(3 points) 16. The standard enthalpy change for the reaction
CaCO3 (s) → CaO (s) + CO2 (g)
Is 178.1 kJ. From the values for the standard enthalpies of formation of CaO (s) and CO2 (g) given in
Appendix 4, calculate the standard enthalpy of formation of CaCO 3 (s).
(3 points) 17. Given the following standard enthalpy change, use the standard enthalpies of formation in
Appendix 4 to calculate the standard enthalpy of formation of CuO (s).
CuO (s) + H2 (g) → Cu (s) + H2O (l)
∆H0 = -129.7 kJ
18.Using values from Appendix 4, calculate the standard enthalpy change for each of the following
reactions:
(3 points) (a) 2 SO2 (g) + O2 (g) → 2 SO3 (g)
(3 points) (b) Mg(OH)2 (s) → MgO (s) + H2O (l)
(3 points) (c) CH4 (g) + 4 Cl2 (g) → CCl4 (l) + 4 HCl (g)
(3 points) (d) SiCl4 (l) + 2 H2O (l) → SiO2 (s) + 4 HCl (g)
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