Question

What mass of propane will produce 4.8 MJ of energy when undergoing complete combustion ?

Answer 1

95.04g are required.

`C_3H_(8(g))+5O_(2(g))rarr3CO_(2(g))+4H_2O_((g))`

`DeltaH_c=-2219kJ`

`M_r` of `C_3H_8 = (3 xx 12) +(8 xx1)= 44`

So 2219 kJ require 44g

So 1kJ requires 44/2219 = 0.0198g

So 1MJ requires `0.0198xx10^(3)"g"` - this is because there are `10^(3)"kJ"` in `1"MJ"`

So 4.8MJ requires `0.0198 xx10^(3)xx4.8 "g"`

= 95.04g