# Determining vapor pressure from equilibrium constant

The reaction is $$CoCl_{2(s)}+6\,H_{2}O_{(g)}\rightleftarrows [Co(H_{2}O)_{6}]Cl_{2(s)}$$

Note that the reaction is at equilibrium. I have determined the value of $K_{p}=5.5\times10^{12}$. The next step in the solution manual is isolating for $P_{H_{2}O}$: $$K_{p}=\dfrac{1}{(P_{H_{2}O})^6}=5.5\times10^{12}$$

How are we justified in making the above expression. Do we make the numerator 1 because the equation is at equilibrium?

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