1. What is Hydroxide Concentration?

Hydroxide concentration ([OH-]) is a measure of the amount of hydroxide ions in a solution. It's inversely related to hydrogen ion concentration ([H+]) through the water ionization constant (Kw).

2. How Does the Calculator Work?

The calculator uses the hydroxide concentration equation:

Where:

• \( [OH^-] \) — Hydroxide ion concentration (mol/L)
• \( K_w \) — Water ionization constant (1×10⁻¹⁴ mol²/L² at 25°C)
• \( [H^+] \) — Hydrogen ion concentration (mol/L)

Explanation: This equation comes from the autoionization of water where \( K_w = [H^+][OH^-] \). The product of [H+] and [OH-] is always constant for aqueous solutions.

3. Importance of [OH-] Calculation

Details: Calculating hydroxide concentration is essential for determining solution pH, understanding acid-base chemistry, and in various chemical and biological processes.

4. Using the Calculator

Tips: Enter [H+] in mol/L (can be in scientific notation like 1e-7). Kw defaults to 1×10⁻¹⁴ mol²/L² (25°C value) but can be adjusted for different temperatures.

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between [OH-] and pH?
A: pH = -log[H+], while pOH = -log[OH-]. In aqueous solutions at 25°C, pH + pOH = 14.

Q2: How does temperature affect Kw?
A: Kw increases with temperature. At 37°C (body temperature), Kw ≈ 2.5×10⁻¹⁴ mol²/L².

Q3: What are typical [OH-] values?
A: In neutral water at 25°C, [OH-] = 1×10⁻⁷ mol/L. Acidic solutions have lower [OH-], basic solutions have higher.

Q4: Can [OH-] be zero?
A: No, even in strong acids there is some [OH-], though extremely small (determined by Kw).

Q5: How is this used in real applications?
A: Used in water treatment, chemical manufacturing, biological systems, and any process where pH control is important.