Concentration of [H+]?

Question

The pH of a solution of NaOH is 11.30. What is the [H+] for this solution?

[a] 2.0*10^-3

[b] 2.5*10^-3

[c] 6.2*10^-8

[d] 5.0*10^-12

[e] None of the above

Answer 1

pOH = 14 - pH = 14 - 11.30 = 2.70

[H+] = 10^-2.70 = 2.0 x 10^-3

[a]

Answer 2

The relevant equation relating pH and concentration of hydrogen ions is as follows:

pH = -log[H+]

Rearranging this equation gives:

[H+] = (inverselog) -pH

Therefore, your answer is [d].