Question

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

• A. $2H_{2} \left(g\right) + O_{2} \left(g\right) \rightarrow 2H_{2}O\left(l\right)$
• B. $2C\left(g\right) + 3H_{2}\left(g\right) \rightarrow C_{2}H_{6}\left(g\right)$
• C. $\frac{3}{2} O_{2}\left(g\right) \to O_{3}\left(g\right)$
• D. $\frac{1}{8}S_{8}\left(s\right) \to O_{2}\left(g\right) \to SO_{2}\left(g\right)$

Answer 1

Answer: (C), (D)

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.