1. What is Water pH/pOH/[OH⁻] Calculation?

The pH, pOH, and hydroxide ion concentration ([OH⁻]) are fundamental parameters that describe the acidity or basicity of aqueous solutions. These values are mathematically related through the ion product of water (K_w = 10⁻¹⁴ at 25°C).

2. How Does the Calculator Work?

The calculator uses the water equilibrium equations:

Where:

• \( pH \) — Negative logarithm of hydrogen ion concentration (unitless)
• \( pOH \) — Negative logarithm of hydroxide ion concentration (unitless)
• \( [OH^-] \) — Hydroxide ion concentration (mol/L)

Explanation: For neutral water at 25°C, pH = 7, pOH = 7, and [OH⁻] = 10⁻⁷ mol/L.

3. Importance of Water pH Measurement

Details: pH measurement is crucial in environmental monitoring, drinking water treatment, industrial processes, and biological systems. It affects chemical reactivity, biological activity, and material corrosion.

4. Using the Calculator

Tips: Enter any one known value (pH, pOH, or [OH⁻]) and the calculator will compute the other two. Leave the fields you want calculated empty.

5. Frequently Asked Questions (FAQ)

Q1: What is neutral water?
A: Neutral water has equal concentrations of H⁺ and OH⁻ ions, resulting in pH = 7, pOH = 7, and [OH⁻] = 10⁻⁷ mol/L at 25°C.

Q2: How does temperature affect these values?
A: The ion product of water (K_w) changes with temperature. At higher temperatures, neutral pH is slightly less than 7.

Q3: What is the relationship between pH and pOH?
A: pH and pOH always sum to 14 in aqueous solutions at 25°C due to the constant ion product of water.

Q4: Can I use this calculator for solutions other than water?
A: Yes, the relationships hold for all aqueous solutions, though the calculated values represent the solution's properties.

Q5: Why are logarithmic scales used?
A: Logarithmic scales (pH, pOH) compress the wide range of ion concentrations (10⁻¹⁴ to 1 M) into a more manageable 0-14 scale.