Question

How do you calculate the enthalpy change in the following reaction 4NH3(g)+5O2(g)→4NO(g)+6H2O?

Answer 1

Answer: The equation used is given below.

Explanation:

Enthalpy change of the reaction is defined as the difference of total enthalpy change of the product and the total enthalpy change of the reactants. It is represented as $\Delta H_{rxn}$. It is negative for exothermic reactions and positive for endothermic reactions.

Equation used for calculating enthalpy change is:

$\Delta H_{rxn}=\sum [n\Delta H_{products}]-\sum[n\Delta H_{reactants}]$

For the given chemical equation:

$4NH_3(g)+5O_2(g)\rightarrow 4NO(g)+6H_2O$

The expression for enthalpy change for this chemical equation follows:

$\Delta H_{rxn}=[(4\times \Delta H_{NO})+(6\times \Delta H_{H_2O})]-[(4\times \Delta H_{NH_3})+(5\times \Delta H_{O_2})]$

Hence, the equation is given above.