Question

Combustion reactions involve reacting a substance with oxy-gen. when compounds containing carbon and hydrogen are combusted, carbon dioxide and water are the products. using the enthalpies of combustion for CH₄ (-2341 kj/mol), C₄H₈ (-2755 kj/mol), and H₂ (-286 kj/mol), calculate ah for the reaction CH₄(g)+2H₂(g) - > CH₂(g)+2H₂(g)

Answer 1

The enthalpy change (ΔH) for the given chemical reaction is calculated as 414 kJ/mol by using the enthalpies of combustion for CH4 and C2H2, and applying Hess's Law.

Step-by-step explanation:

When considering the reaction CH4(g) + 2H2(g) -> C2H2(g) + 2H2(g), the provided enthalpies of combustion are -2341 kJ/mol for CH4, -2755 kJ/mol for C2H2, and -286 kJ/mol for H2. To calculate the enthalpy change (ΔH) for the reaction, we can apply Hess's Law, which states that we can find the enthalpy change for a reaction by adding up the enthalpy changes for individual steps that give the overall reaction.

The direct answer involves the calculation of ΔH using the enthalpies of combustion for CH4 and H2, and employing the reverse enthalpy for the combustion of C2H2 because the process is in the reverse direction. As there is no change in the moles of H2, its enthalpy of combustion does not affect the overall ΔH.

ΔH for the reaction is: ΔHcombustion CH4 - (ΔHcombustion C2H2 * -1) = -2341 - (-2755) = 414 kJ/mol.