1. What is pOH?

pOH is a measure of the hydroxide ion (OH⁻) concentration in a solution. It's the negative logarithm (base 10) of the hydroxide ion concentration and is used to express the alkalinity of a solution.

2. How Does the Calculator Work?

The calculator uses the pOH formula:

Where:

• \( [OH^-] \) — Hydroxide ion concentration in moles per liter (M)
• \( \log_{10} \) — Base-10 logarithm

Explanation: The pOH scale is inversely related to hydroxide ion concentration - as [OH⁻] increases, pOH decreases.

3. Relationship Between pH and pOH

Details: In aqueous solutions at 25°C, pH and pOH are related by: \( pH + pOH = 14 \). This relationship comes from the ion product of water (\( K_w = 1 \times 10^{-14} \)).

4. Using the Calculator

Tips: Enter the hydroxide ion concentration in molarity (M). The value must be positive. For very small concentrations, scientific notation may be helpful (e.g., 1e-7 for \( 1 \times 10^{-7} \)).

5. Frequently Asked Questions (FAQ)

Q1: What is the pOH of pure water at 25°C?
A: Pure water has [OH⁻] = 1 × 10⁻⁷ M, so pOH = 7.

Q2: How does temperature affect pOH?
A: The pH+pOH relationship changes with temperature because \( K_w \) is temperature-dependent. At higher temperatures, pH + pOH < 14.

Q3: What pOH value indicates a basic solution?
A: At 25°C, pOH < 7 indicates a basic solution (pH > 7).

Q4: Can pOH be negative?
A: Yes, for very concentrated bases where [OH⁻] > 1 M, pOH can be negative.

Q5: How accurate is this calculation?
A: This gives theoretical pOH. In practice, activity coefficients may affect results in concentrated solutions.