The table below shows some values for standard enthalpy changes of combustion. Use these values in the table below to calculate the standard enthalpy change of the reaction

Question

C (s) + 2H2 (g) ⇢CH4 (g)

Substance

incrementHc Ө / kJ/mol

C (s)

-394

H2 (g)

-286

CH4 (g)

-890

Answer 1

The standard enthalpy change of the reaction can be calculated by using the formula:

ΔHcӨ(reaction) = ΣΔHcӨ(products) - ΣΔHcӨ(reactants)

ΔHcӨ(reaction) = [-890 kJ/mol] - [(1 x -394 kJ/mol) + (2 x -286 kJ/mol)]

ΔHcӨ(reaction) = -890 kJ/mol + 676 kJ/mol

ΔHcӨ(reaction) = -214 kJ/mol

Therefore, the standard enthalpy change of the reaction C(s) + 2H2(g) ⇢ CH4(g) is -214 kJ/mol.