Question

What is the ph of a solution with a hydroxyl ion (oh-) concentration of 10-10 m? what is the ph of a solution with a hydroxyl ion (oh-) concentration of 10-10 m? ph 10 ph 12 ph 4 ph 2?

Answer 1

PH is the potential of hydrogen. 
pH = -log₁₀(H+) 
while, pOH = -log₁₀(OH-)
But; pH + pOH =14
Therefore; for a solution with a concentration of (OH-) of 10^-10
The pOH= -log(10^-10)
              = 10 
Therefore pH =14-10
                      = 4

Answer 2

According to this formula:
pH = - log [H]
And, pOH = - log [OH] >>> (1)
Where, pH + pOH = 14  >>> (2)
∵ the hydroxide ion concentration = (OH-) = 10 ^ -10 M
from (1) and (2) and by substitution: 
∴ pOH = - log [10^-10] = 10 
∴ pH = 14 - 10 = 4