Why isn't the concentration of water written in Kc (equilibrium constant)?

I always find the answer of this question "because the concentration of water is constant and isn't significantly varied" but i don't really understand this,so could you find a better explanation for me?

1 Answer

  • 9 years ago
    Favorite Answer

    The concentration of water isn't affected because only a very tiny amount of the water ionizes. In pure water, the concentration of hydrogen ion is 1X10^-7M. The hydroxide ion concentration is the same; 1X10^-7M. The remaining water is 55.5M. The Keq would be [H][OH]/[H2O] which is a vanishingly small amount. When compared to the other reactants in solution, water's concentration changes so little that when we count up our significant figures, it just gets rounded off. The concentration isn't really constant, it just changes so little that we don't have to pay attention to it.

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