Question

In which of the following reaction $K_p > K_c$ ?

• A. $PCl_3 + Cl_2 \to PCl_5$
• B. $H_2 + I_2 \to 2HI$
• C. $2SO_3 \to O_2 + 2 SO_2$
• D. $N_2 + 3H_2 \to 2NH_3$

Answer 1

Answer: (C)

$K_{p} = K_{c} \left(RT\right)^{\Delta n}$

$\Delta$ n = change in number of moles

If $\Delta$n = positive then $K_{p}$ will be greater than $K_{c}.$

$PCl_{3} + Cl_{2} \to PCl_{5}, \,\,\Delta n = 1-2 = -1; K_{p} < K_{c}$

$H_{2} + I_{2} \to 2HI, \,\,\Delta n = 0 ; K_{p} = K_{c}$

$2SO_{3} \to O_{2} + 2SO_{2} , \,\,\Delta n = 1; K_{p} > K_{c}$

$N_{2} + 3H_{2} \to 2NH_{3} ; \,\,\Delta n = -2; K_{p} < K_{c}$