1. What is the Water Ionization Constant?

The water ionization constant (Kw) represents the equilibrium constant for the self-ionization of water. At 25°C, Kw = [H+][OH-] = 10⁻¹⁴, indicating the product of hydrogen and hydroxide ion concentrations in pure water.

2. How Does the Calculator Work?

The calculator uses the water ionization constant equation:

Where:

• \( K_w \) — Water ionization constant (unitless)
• \( [H^+] \) — Hydrogen ion concentration (M)
• \( [OH^-] \) — Hydroxide ion concentration (M)

Explanation: The equation calculates the equilibrium constant for water's autoionization reaction: H₂O ⇌ H⁺ + OH⁻

3. Importance of Kw Calculation

Details: Kw is fundamental in acid-base chemistry, pH calculations, and understanding aqueous solution behavior. It helps determine whether a solution is acidic, basic, or neutral.

4. Using the Calculator

Tips: Enter both hydrogen ion concentration [H+] and hydroxide ion concentration [OH-] in molar units (M). All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the standard value of Kw at 25°C?
A: The standard value is 1.0 × 10⁻¹⁴ at 25°C, though it varies with temperature.

Q2: How does temperature affect Kw?
A: Kw increases with temperature because the autoionization of water is endothermic.

Q3: What does Kw = 10⁻¹⁴ indicate about pure water?
A: In pure water at 25°C, [H+] = [OH-] = 10⁻⁷ M, making the solution neutral with pH = 7.

Q4: Can Kw be used for all aqueous solutions?
A: Yes, Kw applies to all aqueous solutions at a given temperature, regardless of other solutes present.

Q5: How is Kw related to pH and pOH?
A: pH + pOH = pKw = 14.00 at 25°C, where pKw = -log(Kw).