In answering this problem we incorporate dimension analysis. We are required to get the amount of the substance given the amount of heat released, molar mass and heat of combustion of the compound. To answer we divide the heat released by the heat of combustion and multiplying the quotient by the molar mass. Make sure units cancel.
=( -543KJ / -1321KJ/mol)*71.83g/mol = 29.55 g
Note: 543.00KJ is negative since the problem states the heat is released (this is a matter of sign convention)
