Question

A solution with pH = 4 has


1. relatively high concentration of OH-

2. relatively low concentration of H3O+

3. relatively high concentration of H3O+

4. zero concentration of OH-

Some of the answers people are giving me are confusing. I just need to know if it 1,2,3 or 4?

Answer 1

pH 4 is a weak acid, so there will be a relatively high concentration of H20 and H+ which makes H3O+. Therefore, there can't be a high concentration of OH-, but that concentration IS NOT 0, because the pH is not very low.

Answer 2

Let me correct you Nan. You may just need to know which answer to choose; however, we try to give you the how without giving the answer. I gave you the HOW to work the problem, I did not give you the answer.

For Aaron, pH = 4 is NOT necessarily a weak acid. A pH = 4 means the H^+ = 1E-4M. A weak acid means the acid is ionized less than 100% so a pH of 4 could be realized by either a weak acid or a strong acid.

For both, I'll repeat that
(H^+)(OH^-) = 1E-14
So if (H^+) = 1E-4, then (OH^-) must be 1E-10.

The problem may not be the best worded in the world since "relatively" is not defined. I agree with Aaron that it can't be answer 4.