Question

based on the bond energies for the reaction below, what is the enthalpy of the reaction, in kj?

h₂(g) + n₂(g) + 2c(g) → 2hcn(g)

Explanation:

Step1: Calculate the energy required to break bonds

• Break \(H - H\) bond: \(432\space kJ/mol\)
• Break \(N\equiv N\) bond: \(942\space kJ/mol\)
• There are no bonds to break for \(2C(g)\) (atomic carbon).
• Total energy to break bonds: \(432 + 942=1374\space kJ/mol\)

Step2: Calculate the energy released when forming bonds

• Each \(HCN\) has \(H - C\equiv N\) bonds.
• For \(2HCN\):
• \(2\) \(H - C\) bonds: \(2\times411 = 822\space kJ/mol\)
• \(2\) \(C\equiv N\) bonds: \(2\times887=1774\space kJ/mol\)
• Total energy released: \(822 + 1774 = 2596\space kJ/mol\)

Step3: Calculate the enthalpy of the reaction

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Answer:

\(-1222\space kJ\)