Home > Chemistry > Chemical Reactions and Equations

An exothermic reaction releases 86.5 kJ. How many kilocalories of energy are released?

Answer 1

#1 " kJ"=0.239" kcal"#

#86.5 " kJ"=86.5*0.239=20.7" kcal"#

Since this problem only involves converting units, it is necessary for you to understand what a calorie is. A calorie is defined as an energy unit equal to 4.184 J, which is the amount of energy needed to heat one gram of water by one degree Celsius at one atmosphere of pressure. If one cal = 4.184 J, then 1000 cal = 4184 J. This means that:

#1 " kcal"=4.184" kJ"#

In terms of kcal, divide both sides by 4.184 to obtain kJ.

#1 " kJ"=0.239" kcal"#

With your conversion factor now obtained, all you have to do is multiply both sides by 86.5.

#1*86.5 " kJ"=0.239*86.5" kcal"#

#86.5 " kJ"=20.7" kcal"#

By signing up, you agree to our Terms of Service and Privacy Policy

Answer 2

Owen Ambrose

The conversion factor 1 kJ = 0.239 kcal can be used to convert kilojoules (kJ) to kilocalories (kcal). Using this factor, you can calculate how many kilocalories of energy are released from 86.5 kJ: 86.5 kJ * 0.239 kcal/kJ = 20.6335 kcal. This means that roughly 20.63 kilocalories of energy are released.

By signing up, you agree to our Terms of Service and Privacy Policy

Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.