The molar heats of combustion of C 2 H 2(g), C (graphite) and H 2(g) are 310.62 kcal , 94.05 kcal and 68.32 kcal respectively. Calculate the standard heat of formation of C 2 H 2(g)

Question

The molar heats of combustion of C 2 H 2(g), C (graphite) and H 2(g) are 310.62 kcal , 94.05 kcal and 68.32 kcal respectively. Calculate the standard heat of formation of C 2 H 2(g) (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

The standard state formation reaction of

C_{2} H_{2} (g)

is :

2 C (g) + H_{2} (g) ⟶ C_{2} H_{2} (g); Δ H_{f}^{\circ}

Δ H_{r}^{\circ} = ΣΔ H_{comb}^{\circ}

(reactants)

- ΣΔ H_{comb}^{\circ}

(products)

= - 2 \times 94.05 - 68.32 - (- 310.62)

= 54.2 k c a l = Δ H_{f}^{\circ} (C_{2} H_{2})

Q. The molar heats of combustion of C2​H2​(g),C (graphite) and H2​(g) are 310.62kcal,94.05kcal and 68.32kcal respectively. Calculate the standard heat of formation of C2​H2​(g)

The standard state formation reaction of C2​H2​(g) is : 2C(g)+H2​(g)⟶C2​H2​(g);ΔHf∘​ ΔHr∘​=ΣΔHcomb ∘​ (reactants) −ΣΔHcomb ∘​ (products) =−2×94.05−68.32−(−310.62) =54.2kcal=ΔHf∘​(C2​H2​)

Q. The molar heats of combustion of $C_{2} H_{2} (g), C$ (graphite) and $H_{2} (g)$ are $310.62 k c a l, 94.05 k c a l$ and $68.32 k c a l$ respectively. Calculate the standard heat of formation of $C_{2} H_{2} (g)$