Energy Unit Conversions

Question

Expressing amounts of energy in different energy units is necessary to solve many chemistry problems. For practice, complete the following table.

The Joule (J) is the SI unit of energy.

1 calorie (cal) = 4.184 J

1 kWh = 3.600 × 10⁶ J

J	kWh	kcal
277
	248
		309

Answer 1

Use dimensional analysis.

277 J x 1 kWh/3.600x10⁶ J = 7.69x10^-5 J

277 J x 1 cal / 4.184 J x 1kcal/1000 cal = 0.0662 kcal

248 kWh x 3.600x10⁶ J/kWh = 8.93x10⁸ J

248 kWh x 3.600x10⁶ J/kWh = 8.93x10⁸ J x 1 cal/4.184 J x 1 kcal/1000 cal = 2.13x10⁵ kcal

You should be able to convert 309 kcal to J and kWh. Give it a try.

J	kWh	kcal
277	7.69x10-5 J	0.0662 kcal
8.93x108 J	248	2.13x105 kcal
		309