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 at standard conditions (25°C).

2. How Does the Calculator Work?

The calculator uses the pOH equation:

Where:

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

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

3. Relationship Between pH and pOH

Details: At 25°C, pH + pOH = 14. This relationship allows conversion between pH and pOH values in aqueous solutions.

4. Using the Calculator

Tips: Enter 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 0.0000001 M).

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 at 25°C.

Q2: How does temperature affect pOH?
A: The pH+pOH relationship changes with temperature. At higher temperatures, the sum is less than 14.

Q3: What pOH value indicates a basic solution?
A: At 25°C, pOH < 7 indicates a basic solution, pOH > 7 indicates acidic, and pOH = 7 is neutral.

Q4: Can pOH be negative?
A: Yes, for very concentrated strong base solutions where [OH⁻] > 1 M, pOH becomes negative.

Q5: How accurate is this calculation?
A: The calculation is mathematically exact, but real solutions may show deviations due to activity coefficients at high concentrations.