Question

Which equilibrium constant expression(s) are for the following reaction. (X stands for the mole fraction of the indicated substance in its phase, which we have so far assumed equal to unity (one) for essentially pure phases.)
Cl2(g) + PCl3(g)↔PCl5(g))

Choose from the list below and enter the letters alphabetical order. (e.g. AH)

(A) (pCl2)eq
(B) (pPCl3)eq
(C) (pPCl5)eq
(D) (pCl2)eq-1
(E) (pPCl3)eq-1
(F) (pPCl5)eq-1
(G) (pCl2)eq2
(H) (pPCl3)eq3
(I) (pPCl5)eq5
(J) (pCl2)eq-2
(K) (pPCl3)eq-3
(L) (pPCl5)eq-5

Answer 1

Answer : The correct alphabetical order will be, CDE

Explanation :

Equilibrium constant : It is defined as the ratio of concentration of products to the concentration of reactants.  It is represented as $K$.

The given balanced equilibrium reaction is,

$Cl_2(g)+PCl_3(g)\rightleftharpoons PCl_5(g)$

As we know that the concentrations of pure solids are constant that means they do not change. Thus, they are not included in the equilibrium expression.

The expression for equilibrium constant for this reaction will be,

$K=\frac{(p_{PCl_5})_{eq}}{(p_{Cl_2})_{eq}(p_{PCl_3})_{eq}}$

or,

$K=(p_{PCl_5})_{eq}\times (p_{Cl_2})_{eq}^{-1}\times (p_{PCl_3})_{eq}^{-1}$

From the expression of equilibrium constant we conclude that the alphabetical order will be, CDE.

Hence, the correct alphabetical order will be, CDE