Ethyne (c2  h2  (g),  hf  = 226.77 kj/mol) undergoes complete combustion in the presence of oxygen to produce carbon dioxide (co2  (g),  hf  = –393.5 kj/mol ) and water (h2  o(g),  hf  = –241.82 kj/mol) according to the equation below.what is the enthalpy of combustion (per mole) of c2  h2  (g)?     use  

Answer : The enthalpy per mole for combustion of  is -1255.6 KJ/mol

Explanation : To find the enthalpy of combustion we need to use the formula as Δ H = 

The reaction is 

On substituting the values in the above equation; we get;

(4 X -393.5) + ((2 X 241.82) - (2 X 226.77) - (5 X 0) = - 2511.2 KJ/ mol

The enthalpy here we get is for 2 moles of which is -2511.2  KJ/mol

we need for one mole of will be -2511.2 / 2 = - 1255.6 KJ/mol