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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: treadlightly on January 26, 2014, 06:00:23 PM

Title: Ion-product constant of Water
Post by: treadlightly on January 26, 2014, 06:00:23 PM

So I am currently confused on a homework problem. The problem at hand says "How much will pH increase if you add 1 mL of 1M KOH to a liter of water?"

I'm pretty sure I have to use the ion-product constant of water for this question. I set up an equation like this: [H+] = Kw/[OH-] = (10^-14)/(.001) = 10^-11, which means that my pH will increase to 11. I'm quite sure I made an error somewhere, because I don't understand how one 1-mL drop of KOH can increase the pH of a liter of water so quickly. Can someone help me out here?

Title: Re: Ion-product constant of Water
Post by: Borek on January 26, 2014, 06:09:02 PM

If it doesn't say anything about initial pH (and solution composition), it is impossible to answer, unless you assume initial pH to be 7.

If the initial pH was 7 pH increased to 11, but not BY 11.

11 is a correct value BTW.