Question

Based on the bond energies for the reaction below, what is the enthalpy of the reaction, in kJ?

H₂(g) + N₂(g) → 2 C(g) + 2 HCN(g)

Answer 1

The enthalpy of the reaction is 1500 kJ.

Step-by-step explanation:

To calculate the enthalpy of the reaction, we need to consider the bond energies of the reactants and products. Let's break down the reaction:

1. H-H bond energy = 436 kJ/mol
2. N-N bond energy = 941 kJ/mol
3. C-C bond energy = 347 kJ/mol
4. H-N bond energy = 389 kJ/mol
5. C-N bond energy = 372 kJ/mol

The energy required to break the bonds in the reactants is:

2 mol of H-H bonds + 1 mol of N-N bonds = 2 x 436 kJ + 941 kJ = 814 kJ

The energy released from forming bonds in the products is:

2 mol of C-C bonds + 2 mol of H-N bonds + 2 mol of C-N bonds = 2 x 347 kJ + 2 x 389 kJ + 2 x 372 kJ = 2314 kJ

Therefore, the enthalpy of the reaction is the difference between the energy required to break the bonds and the energy released from forming the bonds:

Enthalpy = (2314 kJ - 814 kJ) = 1500 kJ