Final answer:
The pH of a bleach solution with a [OH-] of 2.5×10^-5 M is calculated to be 9.40, indicating a basic solution.
Step-by-step explanation:
To calculate the pH of a bleach solution with a hydroxide ion concentration ([OH-]) of 2.5×10-5 M, we need to find its pOH first. The pOH is calculated by taking the negative logarithm (base 10) of the hydroxide ion concentration. Then, to find the pH, we subtract the pOH from 14 because at 25 °C, the sum of pH and pOH for any aqueous solution is 14 (this is a reflection of the ion-product constant for water, Kw, which is 1×10-14 at 25 °C).
The pOH = -log(2.5×10-5) = 4.60.
Next, we calculate the pH: pH = 14 - pOH = 14 - 4.60 = 9.40.
Therefore, the pH of the bleach solution is 9.40, indicating it is basic.