Chemistry (Chang), 10th Edition

Chapter 6: Thermochemistry

Self Assessment B

1
An endothermic process
A)raises the temperature of one gram of a substance by one degree Celcius.
B)takes in heat from the surroundings.
C)increases the acidity of the surroundings.
D)gives off heat to the surroundings.
E)releases carbon dioxide into the surroundings.
2
The chemical equation describing the conversion of SO2 into SO3 is shown below. Calculate DHo when 89.6 g of SO2 is converted into SO 3.

SO2(g) + ½O2(g) ----> SO3(g) DHorxn = -99.1 kJ
A)-69.3 kJ
B)-139 kJ
C)69.3 kJ
D)139 kJ
E)-111 kJ
3
How much energy in calories is required to heat 25.0 g of platinum (specific heat capacity = 0.032 cal/g.K) from 24.5 oC to 75.0 oC?
A)48 cal
B)20. cal
C)80 cal
D)40. cal
E)None of the above.
4
If a substance has a specific heat capacity of 1.0 J/g·oC and a density of 2.0 g/mL, how much energy would be required to raise the temperature of 100 mL of the substance from 25 to 45 oC?
A)0.20 kJ
B)2.0 kJ
C)4 kJ
D)8 kJ
5
A 0.468-g sample of pentane (C5H12) was burned in a bomb calorimeter. The temperature of the calorimeter and the 1.00 kg of water rose from 20.45 to 23.65 oC. The specific heat capacity of the calorimeter is 2.21 kJ/ oC, and the specific heat capacity of water is 4.184 J/g·oC. What is the heat of combustion of one mole of C5 H12?
A)-7.07 x 103 kJ/mol
B)-2.05 kJ/mol
C)-3.16 x 103kJ/mol
D)1.34 x 104 kJ/mol
E)3.16 x 103 kJ/mol
6
Calculate the standard heat of formation of carbon disulfide (CS2) from its elements, C(s) + 2 S(s) ----> CS2(l), given that:

C(s) + O2(g) ----> CO2(g), DH = -393.5 kJ;

S(s) + O2(g) ----> SO2(g), DH = -296.8 kJ; and

CS2(l) + 3 O2(g) ----> CO2(g) + 2 SO2(g), DH = -1076.8 kJ.
A)-1767.1 kJ
B)-386.5 kJ
C)89.7 kJ
D)386.5 kJ
E)None of the above
7
For which of the substances below is DHof = 0?
A)O2(g)
B)N2(l)
C)Na(g)
D)Xe(l)
E)A and B
8
To which of the following reactions occurring a 25 oC does the symbol DHof [H2O(l)] apply?
A)H2O(l) ----> 2 H(g) + O(g)
B)2 H(g) + O(g) ----> H2O(l)
C)H2(l) + ½O2(l) ----> H2O(l)
D)H2(g) + ½O2(g) ----> H2O(l)
E)H2O(g) ----> H2O(l)
9
The heat of solution of KCl is 17.2 kJ/mol, and the combined heats of hydration of one mole of gaseous chloride ions and one mole of gaseous potassium ions is -698 kJ. What is the lattice energy of potassium chloride?
A)-681 kJ/mol
B)715 kJ/mol
C)-715 kJ/mol
D)-332 kJ/mol
E)681 kJ/mol
10
A certain gas expands in volume from 2.0 L to 24.5 L at constant temperature. Calculate the work done by the gas if it expands against a constant pressure of 5 atm.
A)-112.5 J
B)1.24 x 104 J
C)-1.14 x 104 J
D)113 J
E)1.14 x 104 J
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