All isotopes of one element retain the chemical properties of that element.
differ in the number of ions present.
differ in the number of electrons present.
retain the mass number of that element.

The molar mass of methanol is 12.01 + 4.04 + 16 = 32.05 g/mol
230.0 g of methanol / 32.05 g/mol = 7.176 mol methanol
The heat of combustion of methanol (CH3OH or CH4O) is -715.0 kJ/mol. (Negative sign means the energy is released)
Multiplying 7.176 mol by -715.0 kJ/mol gives -5,131 kJ.