pH and pOH Calculator

pH and pOH Equations:

\[ pH = -\log_{10}[H^+] \] \[ pOH = -\log_{10}[OH^-] \] \[ pH + pOH = 14 \text{ (at 25°C)} \] \[ K_w = [H^+][OH^-] = 10^{-14} \]

H⁺ Concentration:

OH⁻ Concentration:

pH:

(unitless)

pOH:

(unitless)

Calculated H⁺ Concentration:

Calculated OH⁻ Concentration:

Calculated pH:

Calculated pOH:

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1. What is pH and pOH?

pH and pOH are measures of the acidity and basicity of a solution. pH is the negative logarithm of the hydrogen ion concentration, while pOH is the negative logarithm of the hydroxide ion concentration. At 25°C, they are related by the equation: pH + pOH = 14.

2. How Does the Calculator Work?

The calculator uses the following equations:

\[ pH = -\log_{10}[H^+] \] \[ pOH = -\log_{10}[OH^-] \] \[ pH + pOH = 14 \] \[ [H^+][OH^-] = 10^{-14} \]

Where:

\( [H^+] \) — Hydrogen ion concentration (molarity)
\( [OH^-] \) — Hydroxide ion concentration (molarity)
\( pH \) — Measure of acidity (0-14 scale)
\( pOH \) — Measure of basicity (0-14 scale)

Explanation: The calculator can compute all four values from any one known value, using the relationships between them.

3. Importance of pH Calculation

Details: pH is critical in chemistry, biology, medicine, and environmental science. It affects chemical reactions, biological processes, and material stability.

4. Using the Calculator

Tips: Enter any one value (H⁺ concentration, OH⁻ concentration, pH, or pOH) and the calculator will compute the other three. All values must be valid (concentrations between 1e-14 and 1 M, pH/pOH between 0-14).

5. Frequently Asked Questions (FAQ)

Q1: What is the pH of pure water at 25°C?
A: Pure water has pH = 7 (neutral), [H⁺] = [OH⁻] = 10⁻⁷ M.

Q2: How does temperature affect pH?
A: The pH of neutral water changes with temperature (pH = 7 only at 25°C). The pH + pOH relationship changes as Kw changes with temperature.

Q3: What's the difference between pH and pOH?
A: pH measures acidity (lower = more acidic), pOH measures basicity (lower = more basic). They are complementary measures.

Q4: Can pH be negative or >14?
A: Yes, for extremely concentrated acids (pH < 0) or bases (pH > 14), though such solutions are rare and require special handling.

Q5: Why use logarithmic scale for pH?
A: The logarithmic scale compresses the wide range of H⁺ concentrations (10⁰ to 10⁻¹⁴ M) into a manageable 0-14 scale.