Question

The decomposition of methanol, ch3oh(g), to form ch4(g) and o2(g) absorbs 252.8 kj of heat per mole of oxygen formed. write a balanced thermochemical equation for this reaction.

Answer 1

The thermochemical equation is the chemical equation including the net change of enthalpy (heat).

The chemical equation for the decomposition of methanol to form methane and oxygen is:

2CH3OH --> 2CH4 + O2

The thermochemical equation is:

2CH3OH ---> 2CH4 + O2  - 252.8 kJ

Note that the heat is placed as negative at the right side because it is absorbed during the decomposition, so the environment will have 252.8 kJ less per each mole of O2 produced.

You can equivalently write:

2CH3OH + 252.8 kJ --> 2CH4 + O2