Question

The equilibrium constant $K_C$ for the reaction, $CaS{O}_4\cdot 5H_{2}O\left(s\right)\rightleftharpoons CaS{O}_4\cdot 3H_{2}O\left(s\right)+2H_{2}O\left(g\right),$ is equal to:

• A. $\frac{[CaS{O}_4\cdot 3H_{2}O][H_{2}O{]}^2}{[CaS{O}_4\cdot 5H_{2}O]}$
• B. $\frac{[CaS{O}_4\cdot 3H_{2}O]}{[CaS{O}_4\cdot 5H_{2}O]}$
• C. $[H_{2}O{]}^2$
• D. $\left[H_{2}O\right]$

Answer 1

The correct option is C $[H_{2}O{]}^2$

The equilibrium constant for the reaction,
$[CaS{O}_4\cdot 5H_{2}O]\rightleftharpoons CaS{O}_4\cdot 3H_{2}O+2H_{2}O\left(g\right),$ is equal to $[H_{2}O{]}^2$
i.e $K_{eqb}=[H_{2}O{]}^2$
Because the concentration of solids (and pure liquids) do not appear in the equilibrium constant expression.
Hence, the correct option C