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

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

Answer 2

Answer:

-1255.6 kJ/mol

Explanation: