Which of the following reactions is defines `Delta_(f)H^(Theta)`?

Options

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

Answer

B

Explanation

`Delta_(f)H^(o)` standard enthalpy of formation definition. (a) does not represent `Delta_(f)H^(o)` because standard state of carbon is graphite and not diamond.