Which of the reaction defines `Delta_(f)H^(@)` ?

Options

A. `C_("diamond")+O_(2)(g)toCO_(2)(g)`
B. `1/2 H_(2)(g)+1/2 F_(2)(g)toHF(g)`
C. `N_(2)(g)+3H_(2)(g)to2NH_(3)(g)`
D. `CO(g)+1/2 O_(2)(g)toCO_(2)(g)`

Answer

B

Explanation

Formation of one mole of its constituents elements is called enthalpy of formation.
In (a) `C_("diamond")` is not constituent element.
In (c ) 2 mole `NH_3` is formed instead of one mole.
In (d) CO is not constituent elemen, it should be carbon.