Answer to Question #220234 in General Chemistry for che

Question

Given the standard enthalpy changes for the following two reactions:

(1) 4C(s) + 5H₂(g)C₄H₁₀(g)...... ΔH° = -125.6 kJ

(2) C₂H₄(g)2C(s) + 2H₂(g)......ΔH° = -52.3 kJ

what is the standard enthalpy change for the reaction:

(3) 2C₂H₄(g) + H₂(g)C₄H₁₀(g)......ΔH° = ?

Answer 1

(3)       2C₂H₄(g) + H₂(g) ----> C₄H₁₀(g)

Δ_rH° = Δ_fH°(C₄H₁₀) – 2Δ_fH°(C₂H₄) – Δ_fH°(H₂) = Δ_fH°(C₄H₁₀) – 2Δ_fH°(C₂H₄) = –125.6 kJ – 2×52.3 kJ = –230.2 kJ.

Δ_rH° = –230.2 kJ.