Question

Methane (CH4) can burn in oxygen (O2) to produce carbon dioxide (CO2) and water (H2O) as outlined in the following equation: CH4 (g) + 2O2 (g) CO2 (g) + 2H2O.Calculate the standard enthalpy change associated with this reaction at 25 °C using thefollowing enthalpies of formation:CH4 ∆Hf = -62.7 kJ·mol–1, CO2 ∆Hf = -393.5 kJ·mol–1, H2O ∆Hf = -285.8 kJ·mol–1.

Answer 1

-902.4kJ/mol

Explanations:

Give the chemical reaction below as shown;

`CH_4(g)+2O_2(g)\rightarrow CO_2(g)+2H_2O(l)`

The standard enthalpy change is expressed as;

`\begin{gathered} \triangle H^o=\triangle H_(f(product))^o-\triangle H^0_(f(reactant)) \\ \triangle H^o=[\triangle H_(CO2)^o+2\triangle H_(H2O)^o]-[\triangle H_(CH4)^o+2\triangle H_(O2)^o] \end{gathered}`

Substitute the given enthalpy change

`\begin{gathered} \triangle H^o=[-393.5+2(-285.8)]-[-62.7+2(0)] \\ \triangle H^o=[-393.5-571.6]+62.7 \\ \triangle H^o=-965.1+62.7 \\ \triangle H^o=-902.4kJmol^(-1) \end{gathered}`

Therefore the standard enthalpy change associated with this reaction is -902.4kJ/mol