Which of the following equation gives the values of heat of formation `(DeltaH_(f)^(@))`?

Options

A. C(diamond) ` + O_(2)(g) rarr CO_(2)(g)`
B. `(1)/(2) H_(2)(g) + (1)/(2)F_(2)(g) rarr HF (g)`
C. `N_(2)(g) + 3H_(2)(g) rarr 2NH_(3)(g)`
D. `H_(2)(g) + F_(2)(g) rarr 3HF(g)`

Answer

B

Explanation

The amount of heat either evoved or absorbed when one gram mole of a substance is formed from its constituent elements, is known as the standard heat of formation `(DeltaH_(f)^(@))`.
Standard state temperature os `25C^(@)` or `298K` and pressure of gaseous substance heat of formation of HF.
`(1)/(2) H_(2)(g) + (1)/(2)F_(2)(g) rarr HF (g), DeltaH_(f)^(@) = ?` (Standard heat of formation of HF (g))