Question

How many moles of isooctane must be burned to produce 100 kJ of heat under standard state conditions? Show all of your work.

Answer 1

`mol_(isooct)= 0.0183 mol`

Step-by-step explanation:

Hi, to calculate the moles needed for that energy requirement, first you need to understand the combustion reaction:

`C_8H_1_8 + 25/2 O_2 \longrightarrow 8 CO_2 + 9 H_2O`

Now, you need the heat of reaction. You can either search for it in tables or calculate it from the heats of formation.

For isooctane:
`\Delta H_(comb)=-5450 kJ/mol`

The last step is just a simple calculation:

`mol_(isooct)=(100kJ)/(5450kJ/mol)`

`mol_(isooct)= 0.0183 mol`

Answer 2

According to Prosen and Rossini, 1945, the standard heat of combustion of isooctane is -5461.3 kJ/mol. The negative sign is just to depict that there was a release of energy. Thus, to produce 100 kJ energy,

100 kJ ÷ 5461.3 kJ/mol isooctane = 0.0183 moles isooctane.

0.0183 moles of isooctane must be burned.

I hope I was able to answer your question J