chem "?" on destroyer.. i dont get it

[Dentista08]

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Choose the CORRECT expression for equilibrium constant, K, of the following reaction at constant temperature and pressure. 3 Fe(s) + 4 H2O(g) « Fe3O4(s) + 4 H2 (g)


A.K = [Fe3O4][H2]4 / [Fe]3[H2O]4B.K = [Fe3O4][H2]4 / [H2O]4C.K = [H2]4 / [Fe]3[H2O]4D.K = [H2]4 / [H2O]4E.K = [Fe3O4] / [Fe]3
I cant understand why its not a?? the explanation says that Fe..etc are pure solids are constant values encorporated into Keq? It just doesn't make sense to me.. 🙁
Thanks 🙂

 

[Thundercatz]

Its not A because you dont include solids in the expression.

 

[Dentista08]

than you for the reply=) but the explanation says pure solids or liquids? I would think water is a pure liquid? Or does it mean that if it's composed with more than 1 atom, it's not pure anymore?

 

[cherr1pop]

it says H2O(g) so it's a gas for that reaction.

 

[Thundercatz]

than you for the reply=) but the explanation says pure solids or liquids? I would think water is a pure liquid? Or does it mean that if it's composed with more than 1 atom, it's not pure anymore?

Yea, H2O is listed as a gas in that expression...hehe

 

[zDDS]

i believe when calculating equilibrium YOU DONT USE SOLIDs (s)

 

[MattEvers]

The concentrations of liquids and solids do not change, therefore they can be left out of the equilibrium equation.

 

[Dentista08]

thanks everyone! Now i get it 🙂 For some reason, equillibrium is my worst topic.. even though i know it should be easy!!!