If the measured pH of an aqueous solution is 2.96, what is [H3O+]? Report your result to 5 decimal places.

Question

If the measured pH of an aqueous solution is 2.96, what is [H3O+]? Report your result to 5 decimal places.

Answer 1

pH = -log [H₃O⁺]

2.96 = - log [H₃O⁺]

[H₃O⁺] = 1x10^-2.96

[H₃O⁺] = 1.09648x10^-3 M (and btw, 5 decimal places is ridiculous)

Answer 2

pH = -log[H3O+]

You can rearrange this equation algebraically to solve for [H3O+]:

-pH = log[H3O+]

10^-pH = 10^(log[H3O+])

**log rule: 10^(logX) = X

So, 10^-pH = [H3O+]

In other words, you can solve for the H3O+ concentration (same as H+) by raising 10 to the power of -pH.