Determine the enthalpy change when 23.5 g of carbon is reacted with oxygen according to the reaction c(s) + o2(g) co2(g) delta h = –394 kj/mol

We are provided with the amount of energy released when one mole of carbon reacts. We mus first convert the given mass of carbon to moles and then compute the energy released for the given amount.

Moles = mass / atomic mass
Moles = 23.5 / 12
Moles = 1.96 moles

One mole releases 394 kJ/mol
1.96 moles will release:
394*1.96
= 772.24

The enthalpy change of the reaction will be -772.24 kJ