To find the concentration of hydronium ions (H+ ions) we use the equation:
pH = - log[H+]
We plug in what we know (pH), then we will do some algebra to solve for [H+]
8.1 = - log[H+]
-8.1 = log[H+] (divided both sides by -1)
10-8.1 = [H+] (use the antilog button on your calculator (10x)
[H+] = 7.9 x 10-9 M
We should always make sure our answer makes sense. In pure water the concentration of H+ ions is 1.0 x 10-7. With a pH of 8.1 the solution is slightly basic, this means we should have less then 1.0 x 10-7 H+ ions and we do, so our answer makes sense.
Nathan B.
tutor
I answered it on your post
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06/06/21
Jay G.
Thank you! How would I solve for the concentration of hydroxide ions?
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06/07/21
Nathan B.
tutor
You use the equation Kw = [H+][OH-]
You rewrite the equation to solve for [OH-] :
[OH-] = Kw / [H+]
You have your [H+] value and Kw is always 1.0 E-14. So you just plug in those numbers and do the calculation.
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06/08/21
Jay G.
Thank you that was so helpful! Do you know how to do this one as well? Identify the oxidation number for this reaction: C12H26 + O2 → H2O + CO2 Is this an example of a redox reaction? How do you know?06/05/21