Question

Question #bf193

Answer 1

You must burn 110.5 g of octane.

You know that 1 mol of octane liberates 5471 kJ of heat.

To liberate 5290 kJ of heat, the mass of octane must be

`5290 cancel("kJ") × (1 cancel("mol C₈H₁₈"))/(5471 cancel("kJ")) × "114.23 g"/(1 cancel("mol C₈H₁₈")) = "110.5 g C₈H₁₈"`

Answer 2

`110.2g` is required.

`C_8H_18+12(1)/(2)O_2rarr8CO_2+9H_2O`

`DeltaH_c=-5471"kJ"`

`M_r=114`

So `5471"kJ"` is produced by `114g`

So `1"kJ"` is produced by `(114)/(5471)g`

So `5290"kJ"` is produced by `(114)/(5471)xx5290=110.2"kJ"`