In which of the following equilibrium equation, `K_pgtK_c`?

Options

A. `2SO_3(g)hArr2SO_2(g)+O_2(g)`
B. `PCl_3(g)+Cl_2(g)hArrPCl_5(g)`
C. `H_2(g)+I_2(g)hArr2HI(g)`
D. `N_2(g)+3H_2(g)hArr2NH_3(g)`

Answer

A

Explanation

`K_p=K_c(RT)^(Deltan_g)`
where `Deltan_g=(n_(gas, pro d))-(n_(gas, react))`
`K_pgtK_c` when `Deltan_g` is positive.
This is true for reaction (1) only.
`Deltan_g=(2+1)-(2)`
`=1`
Note that `Deltan_g` refers to the number of moles of gaseous substances in the balanced equation not in the reaction vessel. For reactions (2) and (4), `Deltan_g` is `-ve`. Thus, `K_p lt K_c`. For reaction (3), `Deltan_g` is zero. Thus, `K_p=K_c`.