1. What is Hydroxide Ion Concentration?

The hydroxide ion concentration [OH⁻] is a measure of the alkalinity of a solution. It's inversely related to pH through the water ionization constant (Kw = 1×10⁻¹⁴ at 25°C).

2. How Does the Calculator Work?

The calculator uses the equation:

Where:

• \( [OH^-] \) — Hydroxide ion concentration in mol/L
• \( pH \) — The pH value of the solution (0-14 scale)
• 14 — The pKw value for water at 25°C

Explanation: This equation derives from the water autoionization equilibrium where \( Kw = [H^+][OH^-] = 1 \times 10^{-14} \) at 25°C.

3. Importance of [OH⁻] Calculation

Details: Knowing hydroxide ion concentration is essential for understanding solution basicity, chemical reaction conditions, and buffer preparation in chemistry.

4. Using the Calculator

Tips: Enter a pH value between 0 and 14. The calculator will provide the corresponding hydroxide ion concentration in both decimal and scientific notation.

5. Frequently Asked Questions (FAQ)

Q1: What's the relationship between pH and pOH?
A: pH + pOH = 14 at 25°C. pOH = -log[OH⁻], just as pH = -log[H⁺].

Q2: What are typical [OH⁻] values?
A: Neutral water at 25°C has [OH⁻] = 1×10⁻⁷ M. Acidic solutions have less, basic solutions have more.

Q3: Does temperature affect this calculation?
A: Yes, Kw changes with temperature. This calculator assumes standard conditions (25°C).

Q4: How precise is this calculation?
A: It's mathematically exact for ideal solutions at 25°C. Real solutions may show slight deviations.

Q5: Can I calculate [H⁺] from this?
A: Yes, [H⁺] = Kw/[OH⁻] = 1×10⁻¹⁴/[OH⁻].