Chapter 8: Thermodynamics
CHM 111 Summer 2013
SI Leader: Kristen Kelly
1. Define the following
a. enthalpy
b. +∆H
c. -∆H
d. entropy
e. gibb's free energy
f. spontaneous (exergonic)
g. nonspontaneous (endergonic)
2. What is the enthalpy change ∆H for a reaction at a constant pressure of 1.00 atm if the internal energy
change (∆E) is 44.0 kJ and the volume increase is 14.0 L? (1 atm= 101.325 J).
3. What is the specific heat of lead if it takes 97.2 J to raise the temperature of a 75.0 g block by 10.0 °C?
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Chapter 8: Thermodynamics
CHM 111 Summer 2013
SI Leader: Kristen Kelly
4. When 25.0 mL of 1.0 M H2SO4 is added to 50.0 mL of 1.0 M NaOH at 25 °C in a calorimeter, the
temperature of the aqueous solution increases to 33.9 °C. Assuming the specific heat of the solution is 4.18
J/ g °C, and that the calorimeter itself absorbs a negligible amount of heat, calculate the ∆H in kJ for the
reaction.
H2SO4 (aq) + 2NaOH → 2H2O (l) + Na2SO4 (aq)
5. Calculate the standard enthalpy change, ΔHo, for the formation of 1 mol of strontium carbonate (the material
that gives the red color in fireworks) from its elements.
Sr (s)  C(graphite )  32 O2 (g)  SrCO3 (s)
The informatio n available is
(1) Sr (s) 
1
2
O2 (g)  SrO (s)
H  - 592 kJ
(2) SrO (s)  CO2 (g)  SrCO3 (s)
H  - 234 kJ
(3) C(graphite )  O2 (g)  CO2 (g)
H  - 394 kJ
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Chapter 8: Thermodynamics
CHM 111 Summer 2013
SI Leader: Kristen Kelly
6. Styrene (C8H8), the precursor for polystyrene polymers, has a standard heat of combustion of -4395 kJ/mol.
Write a balanced equation for the combustion reaction and calculate ∆H°f for styrene in kJ/mol.
∆H°f (H2O) = -285.8 kJ/mol
∆H°f (CO2) = -393.5 kJ/mol
7. Tell whether the following entropy changes are likely to be positive or negative:
a. Deposition (gas to a solid)
b. N2 (g) + 3 H2 (g) → 2 NH3 (g)
c. The fizzing of a newly opened soda
d. The growth of a plant from a seed
8. Use the bond dissociation energy Table 7.1 (pg 1) to combute the ∆H° in kJ for the reaction of ethylene with
hydrogen to yield ethane.
H2C=CH2 (g)
+ H2 (g) → CH3CH3 (g)
9. The boiling point of a substance is defined as the temperature at which liquid and vapor coexist in
equilibrium. Use the heat of vaporization (∆H°vap= 30.91 kJ/mol) and the entropy of vaporization
(∆S°vap=93.2 J/ K mol) to calculate the boiling point (°C) of liquid bromine.
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