A number of the questions on the exam were the same as those done in class.
(Use bond energies to find  DH° for H-H + H2C=CH2 --->  H3C-CH3)

Coffee Cup calorimeter question done in class.

similar K1 at T1 and K2 at T2.  Determine DG°, DH°, DS° etc.

1. Use Hess’s Law to find DH° for the reaction
   C2H2 (g) + 2H2 (g) <---> C2H6(g)

   from the following combustion data:

   C2H2 (g) + 5/2 O2 (g) <---> 2CO2 (g) + H2O (l)
   DH° = -1320 kJ

   H2 (g) + ½ O2 (g) <---> H2O (l)
   DH° = - 285 kJ

   C2H6(g) + 7/2 O2 (g) <---> 2CO2 (g) + 3H2O (l)
   DH° =- 1560 kJ

Answer: -330. kJ

   2.  When a 0.300 g sample of solid camphor (C10H16O) was burned in a bomb
   calorimeter, the temperature of the calorimeter and its contents increased by
   1.54 °C.  When an electric heater delivered 1500 W (1 W = 1 J/s)for 10 s to the
   calorimeter, its temperature changed from 25.30 °C to 27.30 °C.

   Calculate:
   a) the heat capacity of the calorimeter,
Answer: 7.50 kJ/^oC
   b) the change in the internal energy, and
Answer: -11.55 kJ or -5861 kJ/mol
  c) the DH° of combustion per mole of camphor.
Answer: -5870 kJ/mol

   3.  For the reaction 2 SO2 (g) + O2 (g) <---> 2SO3 (g), Kc = 280 at 1000 K.
   a)  What is the value of DG° at 1000 K?
Answer: -10.2 kJ/mol
   b)  If 0.40 mol SO2, 0.18 mol O2, and 0.72 mol SO3 are mixed in a 2.50 L flask
        at 1000 K, in what direction will a net reaction occur?
Answer: Forward direction, DG = -15.2 kJ or Qc<Kc or Q_p<K_{p
                (note need to use} Q_{p and} K_p)

   4.  Calcium oxide (burnt lime) may be prepared by heating calcium carbonate
       (limestone) in a lime kiln, in the following reaction:

        CaCO3 (s) <---> CaO (s) + CO2 (g)

   The value of DH° for this reaction is +178.3 kJ; DS° is +0.1606 kJ/K.  Find the
   temperature at which this reaction becomes spontaneous if the partial pressure of CO2
   is 0.10 atm.
Answer: T = 992 K or 719 ^oC (0.10 atm is Kp at Temp T)