Identify the equation in which change in enthalpy is equal to change in internal energy

Options

A. `2H_(2) O_(2)(l) to 2H_(2)O(l) + O_(2)(g)`
B. `C(s) + O_(2) (g) to CO_(2) (g)`
C. `PCl_(5)(g) to PCl_(3)(g) + Cl_(2)(g)`
D. `N_(2)(g) +3H_(2)(g) to 2NH_(3)(g)`

Answer

B

Explanation

`Delta H = Delta U + Delta n_(g) RT`
In the given options
(a) `2H_(2) O_(2) (l) to 2H_(2) O (l) + O_(2) (g) Delta n_(g) = 1`
`:. Delta H = Delta U + RT`
(b) `C (s) + O_(2) (g) to CO_(2) (g)`
`Delta n_(g) - 1 - 1 = 0`
`:. Delta H = Delta U`
(c ) `PCI_(5) (g) to PCI_(3)(g) + CI_(2)(g)`
`Delta n_(g) = 2 - 1 = 1`
`:. Delta H = Delta U + RT`
(d) `N_(2) (g) + 3H_(2) (g) to 2NH_(3) (g)`
`Delta n_(g) RT = 2 - 3 = - 1`
`:. Delta H = Delta U - RT`
Equation given in option (b) has enthalpy change equal to internal change.