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Writing A Thermochemical Equation
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Background
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Write a balanced equation for the combustion. This is a chapter 6 objective. Check
textbook page 188 (Simple Combustion) for help with this step.
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Consider the molar interpretation of this equation. For example, if the combustion
of one mole of ethane (C2H6) produces 372 kilocalories,
then the following thermochemical equation would be written:
2 C2H6 + 7 O2 ---> 4 CO2 +
6 H2O Q = -744 kcal
The value 744 is 2X the 372 because the equation is balanced for 2 moles of C2H6.
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Finally, notice that the direct proportional relationship between moles and energy
is applicable to any reactant or product. For example, 1488 kilocalories (2X744)
of energy would be produced if 14 (2X7) moles of O2 is consumed. Textbook
Discussion: Sections 7.10 & 7.11, pages 227-232. See Also: Example IX, X, and
XI, pages 228, 229, and 230.
Problem
The combustion of one mole of butane (C4H10)
produces 690 kilocalories. Write the balanced equation
for the combustion of butane. Based on this equation, how many moles
of oxygen gas (O2) will be consumed when the combustion of a sufficient
quantity of butane produces 390 kilocalories?
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