Question

Type the correct answer in the box. Express the answer to two significant figures. Given: N2 + 3H2 → 2NH3 Use the bond energies to calculate the change in enthalpy for the reaction. The enthalpy change for the reaction is [ ]kilojoules.

Answer 1

Explanation:

Enthalpy change is defined as in a chemical reaction the amount of energy absorbed or evolved in the form of heat at constant pressure.

For the given reaction, $N_{2} + 3H_{2} \rightarrow 2NH_{3}$ calculate the enthalpy change as follows.

   $\Delta H$ = Bond energy of reactants - Bond energy of products

                                 = {[(2 × 942) + (3 × 432)] - [6 × 386]} KJ/mol

                                 =   {[1884 + 1296] - 2316} KJ/mol

                                 = {3180 -2316} KJ/mol

                                 = 864 KJ/mol

Thus, we can conclude that the enthalpy change for the given reaction is 864 KJ/mol.