1. What Is The pH Calculation For Weak Acid?

This calculator determines the pH of a weak acid solution with a fixed concentration of 0.0008 M using the approximation formula [H⁺] = √(Ka × C). The pH is then calculated as -log[H⁺].

2. How Does The Calculator Work?

The calculator uses the formula:

Where:

• \( K_a \) — Acid dissociation constant (mol/L)
• \( C \) — Fixed concentration of 0.0008 mol/L
• \( [H^+] \) — Hydrogen ion concentration = \( \sqrt{K_a \times C} \)

Explanation: This approximation is valid for weak acids where the concentration of H⁺ ions comes primarily from the acid dissociation.

3. Importance Of pH Calculation

Details: pH calculation is essential in chemistry, biology, and environmental science for understanding acid-base properties, reaction kinetics, and biological processes.

4. Using The Calculator

Tips: Enter the acid dissociation constant (Ka) in mol/L. The value must be greater than 0. The concentration is fixed at 0.0008 M as specified.

5. Frequently Asked Questions (FAQ)

Q1: Why is the concentration fixed at 0.0008 M?
A: This calculator is specifically designed for weak acid solutions with a molarity of 0.0008 M as specified in the problem statement.

Q2: When is this approximation valid?
A: This approximation works well for weak acids where Ka is much smaller than the concentration, typically when Ka/C < 0.01.

Q3: What are typical Ka values for weak acids?
A: Weak acids typically have Ka values between 10⁻² and 10⁻¹⁰. Common examples include acetic acid (Ka = 1.8 × 10⁻⁵) and hydrofluoric acid (Ka = 6.8 × 10⁻⁴).

Q4: How accurate is this approximation?
A: The approximation becomes less accurate for stronger weak acids or very dilute solutions. For precise calculations, the quadratic formula should be used.

Q5: Can this calculator be used for strong acids?
A: No, this calculator is specifically designed for weak acids. Strong acids completely dissociate and require different calculation methods.