Which is the strongest base?
[h+] = 10^-9
[h+] = 10^-11
[h+] = 10^-10
[h+] = 10^-12

The answer to your question is: [H+] = 10⁻¹²

Explanation:

Remember that pH = -log [H+], then, in this exercise we need to calculate the pH of the substances and compare the results, the one which the higher value will be the strongest base.

a) [H+] = 10^-9      pH = -log[10⁻⁹] = 8

b) [H+] = 10^-11     pH = -log[10⁻¹¹] = 10

c) [H+] = 10^-10     pH = -log[10⁻¹⁰] = 9

d) [H+] = 10^-12    pH = -log[10⁻¹²] = 11      This is the strongest base

c is the answer because when something is left after something evaporates that shows the chemical change.