6.7: Thermochemistry Chapter 7 University of Arkansas at Little Rock Dr. Robert Belford

The Following Questions Deal with the combustion of a low grade sample of coal with a weight % composition of: 11.7% sulfur and 88.3% carbon. You are given the following enthalpies of formation ΔHf(CO2) = -393.5 KJ/mol, ΔHf(H2O(l)) = -285.0 KJ/mol & ΔHf(SO2) = -296.8 KJ/mol

Question 1
 Determine the enthalpy change when 1.00 kg of carbon combusts (A)  32.7MJ (B)  -32.7MJ (C)  -65.5MJ (D)  None of the above Hint

Question 2
 Determine the enthalpy change when 1.00 kg of sulfur comubusts (A)  9.27kJ (B)  9.27MJ (C)  -9.27MJ (D)  -9.27kJ Hint

Question 3
 3. Determine the enthalpy change when 1.00 kg of coal combusts (use the above percent composition) (A)  -30.0MJ (B)  -32.7 MJ (C)  41.9MJ (D)  none of the above Hint

Question 4
 How many grams of water can be boiled if the water is initially at 30. deg. C and all the heat is transferred from the combustion of 1.00 kg of the above coal. The enthalpy of vaporization for water is 44.0kJ/mol. (A)  10.9kg (B)  5.8okg (C)  20.8kg (D)  none of the above Hint