Final answer:
The pOH of an aqueous solution with a hydroxide ion concentration of 3.98 × 10^-9 M at 25 °C, use the formula pOH = -log[OH-]. The calculated pOH is approximately 8.4, indicating a basic solution.
Step-by-step explanation:
The POH of a solution can be calculated using the concentration of hydroxide ions (OH-) present in the solution. At 25 °C, the relationship between pOH and hydroxide ion concentration is given by the formula: pOH = -log[OH-].
Given the hydroxide ion concentration is 3.98 × 10-9 M, we can calculate the pOH:
pOH = -log(3.98 × 10-9)
Using a calculator, we find:
pOH ≈ 8.4
Furthermore, since we know that at 25 °C, the sum of pH and pOH is always equal to 14.00 (14.00 = pH + pOH), we can infer that a higher pOH corresponds to a more basic solution and a lower pOH to a more acidic solution.