Consider the following cases of standard enthalpy of reaction (ΔH°ᵣ in kJ mol⁻¹) C₂H₆(g) + 7/2 O₂(g) → 2CO₂(g) + 3H₂O(l) ΔH°₁ = −1550 C(graphite) + O₂(g) → CO₂(g) ΔH°₂ = −393.5 H₂(g) + 1/2 O₂(g) → H₂O(l) ΔH°₃ = −286 The magnitude of ΔH°f(C₂H₆(g)) is _______ kJ mol⁻¹ (Nearest integer).

Question

Dr. Abubacker · Accepted Answer

[Solution by Dr. Abubacker] $\Delta H_1=2\Delta H_2+3\Delta H_3-\Delta H_f(\mathrm{C_2H_6})$, so $\Delta H_f=2(-393.5)+3(-286)+1550=-787-858+1550=-95$ kJ mol⁻¹. The magnitude is 95. Answer: 95.

Explanation

Reviewed by Dr. Abubacker

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