Question

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 1

-1255.6 kJ/mol

Step-by-step explanation:

Answer 2

Answer : The enthalpy per mole for combustion of
`C_(2) H_(2)` is -1255.6 KJ/mol

Explanation : To find the enthalpy of combustion we need to use the formula as Δ H =
`H_(products) - H_(reactants)`

The reaction is
`2C_(2)H_(2) + 5O_(2) ----\ \textgreater \ 4CO_(2) + 2H_(2)O`

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
`C_(2)H_(2)` which is -2511.2 KJ/mol

we need for one mole of
`C_(2)H_(2)` will be -2511.2 / 2 = - 1255.6 KJ/mol