Choose the reactions) from the following options, for which the standard enthalpy of reaction is equal to the standard enthalpy of formation.

Question

Choose the reactions) from the following options, for which the standard enthalpy of reaction is equal to the standard enthalpy of formation. (A) 2H2 (g) + O2 (g) arrow 2H2O(l) (B) 2C(g) + 3H2(g) arrow C2H6(g) (C) (3/2) O2(g) → O3(g) (D) (1/8)S8(s) → O2(g) → SO2(g)

Tardigrade Admin · Accepted Answer

Since standard enthalpy of formation of a compound is the change in the standard enthalpy when one mole of the compound is formed starting from requisite amount of constituent elements in standard state.
Hence only (C) and (D) options are correct.

Q. Choose the reactions) from the following options, for which the standard enthalpy of reaction is equal to the standard enthalpy of formation.

$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (l)$

$2 C (g) + 3 H_{2} (g) \to C_{2} H_{6} (g)$

$\frac{3}{2} O_{2} (g) \to O_{3} (g)$

$\frac{1}{8} S_{8} (s) \to O_{2} (g) \to S O_{2} (g)$

Since standard enthalpy of formation of a compound is the change in the standard enthalpy when one mole of the compound is formed starting from requisite amount of constituent elements in standard state.
Hence only (C) and (D) options are correct.

Q. Choose the reactions) from the following options, for which the standard enthalpy of reaction is equal to the standard enthalpy of formation.

2H2​(g)+O2​(g)→2H2​O(l)

2C(g)+3H2​(g)→C2​H6​(g)

23​O2​(g)→O3​(g)

81​S8​(s)→O2​(g)→SO2​(g)

Since standard enthalpy of formation of a compound is the change in the standard enthalpy when one mole of the compound is formed starting from requisite amount of constituent elements in standard state. Hence only (C) and (D) options are correct.

$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (l)$

$2 C (g) + 3 H_{2} (g) \to C_{2} H_{6} (g)$

$\frac{3}{2} O_{2} (g) \to O_{3} (g)$

$\frac{1}{8} S_{8} (s) \to O_{2} (g) \to S O_{2} (g)$

Since standard enthalpy of formation of a compound is the change in the standard enthalpy when one mole of the compound is formed starting from requisite amount of constituent elements in standard state.
Hence only (C) and (D) options are correct.