Thermochemistry Worksheet

  1. A laboratory volcano can be made from ammonia dichromate. When ignited, the compound decomposes into a fiery display. If the decomposition of 1mol ammonium dichromate produces 315kJof heat energy at a constant pressure, how much heat energy would be produced by 28.3g of the solid?

(NH4)2Cr2O7(s)  N2(g) + 4H2O(g) + Cr2O3(s)

  1. How many kilojoules of heat are evolved by a reaction in a calorimeter, where the temperature of 320.0g water increases from 19.5˚C to 22.83˚C? Given: The specific heat capacity of water is 4.186J/gK.
  2. Suppose you pick up a 16Kg “shot-put” (ball of iron) at a track event. The iron ball has the same temperature as the atmosphere on a cool day, 16˚C. How many calories of heat energy must the iron ball absorb to reach the temperature of your body, 37˚C? Given: The specific heat capacity of iron is 0.460J/gK.
  3. How many kilocalories of heat energy are required to heat all of the aluminum in a roll of aluminum foil, 500g, from room temperature25˚C to the temperature of a hot oven 250˚C? Given: The specific heat capacity of aluminum is 0.900J/gK.
  4. Calculate the amount of heat released from the combustion of 35.0g of propane gas, C3H8. Given: The molar heat of combustion for propane is 2220kJ/mol.
  5. Using the amount of heat released from the propane in problem five to warm up 200g of water, what would be the change in temperature of the water?The specific heat capacity of water is 4.186J/gK.
  6. How much octane, C8H18, should go through combustion to produce 10,000kJ of energy? Given: The molar heat of combustion for octane is 5471kJ/mol.
  7. When 5.8g of methane gas, CH4, reacts with oxygen gas to produce carbon dioxide gas and water vapor, 320kJ of energy is released. Calculate the molar enthalpy of combustion for methane in kJ/mol?
  8. What is the molar enthalpy of formation of diamonds from graphite given the following information? C(s, graphite) C(s, diamond) ΔHrxn = xkJ

C(s, graphite) + O2(g) CO2(g)ΔHrxn = -393.5kJ

C(s, diamond) + O2(g) CO2(g)ΔHrxn = -395.4kJ

  1. What is the molar enthalpy of the formation of 2mol NO gas given the following information? N2(g) + O2(g)  2NO(g) ΔHrxn = xkJ

4NH3(g) + 3O2(g) 2N2(g) + 6H2O(g)ΔHrxn = -1530kJ
4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)ΔHrxn = -1170kJ

  1. The reaction for the combustion of butane is …

2C2H10(g) + 13O2(g)  8CO2(g) + 10H2O(g)ΔHrxn = -4345kJ

  1. Is this reaction endothermic or exothermic?
  2. Calculate the number of grams of butane needed to produce 134.0J of energy.