# The [OH1-] with a pH of 5 is

## the pOH is 9, so OH conc is 10^-5

## 10-9 or 10-5 bobpursely

## (OH^-) = 10^-9 is correct.

## To determine the hydroxide ion concentration ([OH-]) given a pH value of 5, we need to use the equation for the relationship between pH and pOH.

The pH scale is a logarithmic scale that measures the concentration of hydrogen ions ([H+]) in a solution. The pOH scale is also a logarithmic scale that measures the concentration of hydroxide ions ([OH-]) in a solution. The sum of pH and pOH in any solution at a given temperature is always equal to 14.

The equation to calculate pOH is:

pOH = 14 - pH

Substituting the given pH value of 5 into the equation:

pOH = 14 - 5

pOH = 9

Now that we have the pOH value, we can determine the hydroxide ion concentration ([OH-]) using the equation:

[OH-] = 10^(-pOH)

Substituting the pOH value of 9 into the equation:

[OH-] = 10^(-9)

Calculating this mathematically, we find:

[OH-] = 1 x 10^(-9) or 0.000000001 M

Therefore, the hydroxide ion concentration ([OH-]) with a pH of 5 is approximately 0.000000001 M.