Question

Complete combustion of 1.0 metric ton of coal (assuming pure carbon) to gaseous carbon dioxide releases 3.3 x 10^10 J of heat. Convert this energy to kilocalories

a) 7.9 x 10^9 kcal
b) 1.4 x 10^8 kcal
c) 7.9 x 10^6 kcal
d) 1.4 x 10^11 kcal
e) None of these is within 5% of the correct answer

Answer 1

To convert the energy released by the combustion of coal from Joules to kilocalories, divide 3.3 x 10^10 J by the Joule to calorie conversion factor and then convert to kilocalories, resulting in 7.9 x 10^6 kcal.

Step-by-step explanation:

To convert the energy from Joules to kilocalories, we will use the conversion factor where 1 calorie is equivalent to 4.184 Joules. Knowing that 1 kilocalorie is 1,000 calories, we can perform the following calculation:

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• First, find the number of calories by dividing the energy in Joules by the conversion factor:
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• (3.3 x 1010 J) / (4.184 J/cal) = 7.882 x 109 cal
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• Next, convert calories to kilocalories by dividing by 1,000:
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• (7.882 x 109 cal) / (1,000 cal/kcal) = 7.882 x 106 kcal

Thus, the correct answer is c) 7.9 x 106 kcal.