Question

The molar heat of combustion of c2h2, carbon and hydrogen are 1300 kj, 393.5 kj and 282.6 kj respectively. The enthalpy of c2h2 in kj mol1 is:

Answer 1

Answer:

The enthalpy of C₂H₂ = 230.4 kJ/ mol

Explanation:

Given

Molar heat of combustion of C₂H₂ = 1300 kJ

Molar heat of combustion of carbon = 393.5 kJ

Molar heat of combustion of hydrogen = 282.6 kJ

Enthalpy of C₂H₂ = ??

Solution

From the given data, we can write:

H₂ + 1/2 O₂ ----------> H₂O                      ΔH = -282.6 kJ

2 C + 2 O₂ -----------> 2 CO₂                   ΔH = -393.5 x 2 kJ

2 CO₂ + H₂O ---------> C₂H₂ + 5/2 O₂     ΔH = 1300 kJ

Adding the above three equations we get

2 C + H₂ -----------> C₂ H₂                        ΔH = -282.6 + (-787.0) + 1300  

                                                               ΔH = 230.4 kJ/ mol

We will get 1 mol of C₂ H₂  thus enthalpy will be for one mol,

Hence, the enthalpy of C₂H₂ = 230.4 kJ/ mol