Question

I'm not sure how to do this Chemistry question: 
A suggested method for generating chlorine involves the reaction 
4HCl (g) + O2 (g) -------> 2Cl2 (g) + 2H2O (l) 
Calculate the change in enthalpy for this reaction, given that the enthalpies of formation of H2O (l) and HCl (g) are 286kJmol^-1 and 92kJmol^-1 respectively.

Answer 1

enthalpy of reaction is 286-92 =194kj/mole