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Moderate

$K$ for Heterogeneous Equilibria

APCHEM-LVEC1K

$$Ca{ Cl }_{ 2 }(s)+2{ H }_{ 2 }O(g)\rightleftharpoons CaC{ l }_{ 2 }\cdot 2{ H }_{ 2 }O(s)$$

Consider the reaction shown above for the hydration of solid calcium chloride.

Which of the following CORRECTLY gives the equilbrium law expression for this reaction?

A

$K=\cfrac { \left[ CaC{ l }_{ 2 }\cdot 2{ H }_{ 2 }O \right] }{ \left[ Ca{ Cl }_{ 2 } \right] { \left[ { H }_{ 2 }O \right] }^{ 2 } } $

B

$K=\cfrac { 1 }{ { \left[ { H }_{ 2 }O \right] }^{ 2 } } $

C

$K=\cfrac { 1 }{ 2\left[ { H }_{ 2 }O \right] } $

D

$K={ \left[ { H }_{ 2 }O \right] }^{ 2 }$