Thermochemistry Practice Problems

1.What will be sign for q and W if an isolated system absorb energy from the surrounding and does work for expansion.

2. The amount of work done in joules by the system in expanding from 1.50L to 2.3L against a constant atmospheric pressure of about 1.3atm.

3. Calculate the internal energy change of a system that release 520kJ heat energy to the surrounding. Surrounding does a work of 120kJ on the system.

4. How much calories of heat energy is needed to ruse the temperature of 540mL of water from 32.00C to 95.00C?

5. 1421J of heat is required to raise the temperature of 350g of metal by 32.00C. Find the specific heat capacity of the metal.

6. Find the final temperature if 150.0mL of water at 90.00C is added to 100.00mL of water at 30.00C.

7. 25.6g of ethanol is burned in a bomb calorimeter that has a heat capacity of 6.53kJ/0C. The initial temperature of the calorimeter is 24.00C. Find its final temperature

C2H5OH(l) + 3O2(g) -----> 2CO2(g) + 3H2O(g) ΔHrxn= -1235kJ

8. Two solutions initially at 24.600C are mixed in a coffee cup calorimeter that has a heat capacity of 15.5J/0C. When a 100.0mL volume of 0.100M AgNO3 solution is mixed with a 100.0mL sample of 0.200M NaCl solution, the temperature in the calorimeter rises to 25.300C. determine the ΔHrxn for the reaction as written below.

NaCl(aq) + AgNO3(aq) -----> AgCl(s) + NaNO3(aq)

9. Use the standard enthalpies given below to determine ΔHrxn for the following reaction:

P4(g) + 10Cl2(g) -----> 4PCl5(s)

Given;

PCl5(s) -------> PCl3(g) + Cl2(g) ΔHrxn = 157kJ

P4(g) + 6Cl2(g)-----------> 4PCl3(g) ΔHrxn = -1207Kj

10. Use the information to find the ΔHrxn for the following reaction:

CH4(g) + 4Cl2(g) ---------> CCl4(g) + 4HCl(g) ΔHrxn= ?

ΔH 0 f (kJ/mol)

CH4(g) -75

CCl4(g) -96

HCl -92

Reference: Thermochemistry Practice problems. El Camino College.