AP Chemistry - Thermodynamics Test
1. A 25.0 g sample of an alloy was heated to 100.0 oC and dropped into a beaker containing 90.0 g of water at 25.32oC. The temperature of the water rose to a final value of 27.18oC. Neglecting heat lost to the air and the beaker itself, what is the specific heat of the alloy?
2. How much heat is given up when 20 g of steam at 110.0 oC are condensed and cooled to 20oC?
3. The chemical equation for the combustion of ethene is
C2H4 (g) + 3 O2 (g)è 2 CO2(g) + 2 H2O(l) ΔH = -337 kcal/mol
If 38.00 g of ethene are burned and all of the heat is used to heat water from 0.00 to 98.5oC, how many grams of water are being heated?
4. What is the bond energy of one of the resonant bonds in SO3? (You know the one that isn't really a sinlge bond and isn't really a double.)
Helpful facts:ΔHfo of SO3(g) = -395.7 kJ/mol,
Sulfur naturally occurs as S8, a cyclic molecule,
S-S = 215 kJ/mol,
O-O = 140 kJ/mol,
O=O = 498 kJ/mol
5. Use the data below to solve the following problems:
ΔHfo Sfo ΔGfo
(kJ/mol) (J/mol K) (kJ/mol)
NO2(g) 33.2 239.9 51.30
N2O4 (g) 9.16 304.2 97.82
a) At what temperature will this reaction be neither spontaneous nor non-spontaneous?
2 NO2(g) ---> N2O4 (g)
b) If you wanted this experiment to NOT run spontaneously would you need a higher or lower temperature?
6. Calculate the heat of the following reaction:
Fe2O3(s) + 3 CO(g) ---> 2 Fe (s) + 3 CO2(g)
using the following information:
3 Fe2O3 (s) + CO (g) ---> 2 Fe3O4 (s) + CO2 (g) ΔH = -46.4 kJ
FeO (s) + CO (g) ---> Fe (s) + CO2 (g) ΔH = 9.0 kJ
Fe3O4 (s) + CO (g) ---> 3 FeO (s) + CO2 (g) ΔH = -41.0 kJ
7. What is the sign on q when a reaction is exothermic and why?
8. What is the difference between a system doing work and work being done on a system. Use an example to explain.
9. An experiment is done using a coffee cup calorimeter.
a) To determine the heat capacity of the calorimeter 120 g of water at 21.0oC are placed in the cup. 130 g of water at 71oC are poured into the cup and the temperature rises to 43.5oC. Calculate the heat capacity of the calorimeter.
b) A reaction is run in the calorimeter that does not effect the specific heat of the water. If the calorimeter holds 140.0 g of water at 29oC and the reaction causes the temperature to rise to 31oC, how much heat was generated?
Some things you might need to know:
R = 8.314 J/K
There are 4.184 J/1 cal
Specific heat of water is 1.00 cal/goC, or 4.184 J/g oC
The specific heat of steam is 0.491 cal/goC
The heat of vaporization of water is 40.7 kJ/mol