[CHM 330] 4.19

[Andrew J. Pounds]

So I have gotten several questions today about 4.19.  Many of you are 
confusing K with Kw.

Kw=[H+][OH−]K_w=[H_3O^+][OH^-]

You need to find K for the dissociation of water, which has to include 
the molarity of water.

K=[H+[OH−][H2O]K=\frac{[H^+[OH^-]}{[H_2O]}

The molarity of H+ and OH- you can find from the pH.  The molarity of 
water is found by dividing the moles of water by volume. 1 L of water 
weighs 1000 g.  1000 g / 18 g/mol = 55.6 molar.

For the last part you can look up the enthalpy of the reactin in table 
4.2 and then use equation 4.53 in your text to compute the equilibrium 
constant at the other temperature.


-- 
*/Andrew J. Pounds, Ph.D./*
/Professor of Chemistry and Computer Science/
/Director of the Computational Science Program/
/Mercer University, Macon, GA 31207 (478) 301-5627/
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