1. What is pH?

pH is a measure of the acidity or basicity of an aqueous solution. It is defined as the negative logarithm (base 10) of the hydrogen ion concentration. The pH scale typically ranges from 0 to 14 in aqueous solutions at 25°C.

2. How Does the Calculator Work?

The calculator uses the pH formula:

Where:

• \( [H^+] \) — Hydrogen ion concentration in moles per liter (mol/L or M)
• \( \log_{10} \) — Logarithm base 10

Explanation: The pH value decreases as hydrogen ion concentration increases, with each whole pH value below 7 representing a tenfold increase in acidity.

3. pH Scale and Interpretation

pH Scale:

• 0-2: Strong acid (e.g., battery acid)
• 3-6: Weak acid (e.g., vinegar, coffee)
• 7: Neutral (pure water)
• 8-11: Weak base (e.g., sea water, baking soda)
• 12-14: Strong base (e.g., bleach, drain cleaner)

4. Using the Calculator

Tips: Enter the hydrogen ion concentration in mol/L (molarity). The value must be positive. For very small concentrations, scientific notation may be helpful (e.g., 1×10⁻⁷).

5. Frequently Asked Questions (FAQ)

Q1: What's the pH of pure water?
A: At 25°C, pure water has a pH of 7 (neutral) with [H⁺] = 1×10⁻⁷ M.

Q2: Can pH be negative or greater than 14?
A: Yes, for very strong acids (pH < 0) or very strong bases (pH > 14), though these are uncommon in most applications.

Q3: How does temperature affect pH?
A: The neutral point changes with temperature (e.g., pH 6.14 at 100°C), though the calculator assumes standard conditions (25°C).

Q4: What's the relationship between pH and pOH?
A: pH + pOH = 14 at 25°C. pOH measures hydroxide ion concentration similarly to how pH measures hydrogen ion concentration.

Q5: How accurate is this calculator?
A: It provides theoretical pH based on concentration alone. Real solutions may differ due to activity coefficients, ionic strength, and other factors.