1. What is the pH Calculation for Weak Base?

The pH calculation for a weak base like ammonia (NH₃) involves determining the hydroxide ion concentration from the base dissociation constant (Kb) and the initial concentration of the base. The formula accounts for the partial dissociation of the weak base in aqueous solution.

2. How Does the Calculator Work?

The calculator uses the pH calculation formula:

Where:

• \( K_b \) — Base dissociation constant (mol/L)
• \( C \) — Initial concentration of weak base (mol/L)
• \( \sqrt{K_b \times C} \) — Approximation for [OH⁻] concentration

Explanation: For weak bases where Kb is small and concentration is reasonable, the hydroxide ion concentration can be approximated as the square root of (Kb × C). The pH is then calculated from the pOH.

3. Importance of pH Calculation

Details: Accurate pH calculation is essential for understanding chemical behavior in solution, predicting reactivity, and controlling chemical processes. For ammonia solutions, pH affects its properties as a cleaning agent, fertilizer component, and industrial chemical.

4. Using the Calculator

Tips: Enter the base dissociation constant (Kb) in mol/L and the initial concentration (C) in mol/L. For ammonia (NH₃), Kb = 1.8×10⁻⁵ mol/L. Default values are set for 0.1 M NH₃ solution.

5. Frequently Asked Questions (FAQ)

Q1: Why use this approximation for weak bases?
A: This approximation is valid when Kb is small and the concentration is not too dilute, allowing simplification of the equilibrium calculation.

Q2: What is the Kb value for ammonia?
A: The base dissociation constant for ammonia (NH₃) is 1.8×10⁻⁵ mol/L at 25°C.

Q3: When is this approximation not valid?
A: This approximation may not be accurate for very dilute solutions or for bases with relatively large Kb values where the dissociation is more significant.

Q4: How does temperature affect the calculation?
A: Kb values are temperature-dependent. The calculation assumes standard room temperature (25°C). For precise work, use Kb values at the appropriate temperature.

Q5: Can this calculator be used for other weak bases?
A: Yes, this calculator can be used for any weak base by entering the appropriate Kb value and concentration.