Question

The enthalpy of combustion of octane is -5470 kJ/mol. Octane (formulae C8H18) was used to heat some water in a copper can. The amount of octane used up was 0.1 g. The amount of water in the can was 100 cm3 . a) Find the moles of octane which was used up. (Show calculations)

Answer 1

Answer: 0.0009 moles of octane were used up.

Explanation:

To calculate the moles :

$\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}$

Given mass of octane = 0.1 g

Molar mass of octane = 11.23 g/mol  

Putting in the values we get:

$\text{Moles of octane}=\frac{0.1g}{114.23g/mol}=0.0009moles$

Thus 0.0009 moles of octane were used up.