Determining Energy available from combustion

Question

We are trying to find out the Energy available from combustion of different sources of fuels. How do you calculate that?

Answer 1

If you are trying to calculate this from data provided, you do it one way. If you are trying to determine this experimentally, you do it quite a different way. I'll assume you are given thermodynamic data for each fuel, and are asked to calculate the energy produced upon complete combustion. This is best illustrated using examples. For example, compare butane (C4H10) to octane (C8H18).

From a table of ∆Hcombustion, I find the following values:

Butane = 2878 kJ/mol

Octane = 5470 kJ/mol

So, it is easy to see that 1 mole of octane will generate almost twice as much heat (1.9x) as 1 mole of butane.

The short answer to your question is that you simply look up the ∆Hcombustion of the different fuels and compare them. If this isn't what you meant to ask, please respond in the "comment" section below.