Answer:
See explanation below
Step-by-step explanation:
If [OH | = 1x 10^-7 M then [H^+] = 1 * 10^-14/1x 10^-7 = 1x 10^-7 M
pH = - log [H^+] = -log [1x 10^-7]
pH = 7
If [OH | = 1x 10^-9 M then [H^+] = 1 * 10^-14/1x 10^-9 = 1x 10^-5 M
pH = - log [H^+] = -log [1x 10^-5]
pH = 5
[H^+] = 1 x 10^-3 M
pH = - log [H^+] = -log [1x 10^-3]
pH = 3
Hence the decreasing acidity;
pH 3 > pH 5 > pH 7 > pH 11
The most acidic is pH 3 while the most basic is pH 11