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
 
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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
 
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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
 
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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
 
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Question 5
How many moles of sulfurous acid could be created if all the sulfur dioxide produced reacts with water
(A)  62.4
(B)  44.8
(C)  31.2
(D)  none of the above
 
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Question 6
What volume of 0.100M sulfurous acid solution could be created by the combustion of 1 kg of the above coal.
(A)  3.00L
(B)  312L
(C)  3.10ML
(D)  none of the above
 
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