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#Ka

19 public questions tagged with this topic.

A weak acid HY ( Ka = 2.0 × 10⁻⁵ ) is mixed with 0.01 M NaOH in a 2:1 volume ratio (acid:base). If the final [HY] = 0.04

Let volumes be 2V and V, total volume = 3V. Moles: HY = 0.04 × 3V , initial [HY] = 0.06 M , moles NaOH = 0.01V , [Y-] = (0.01V/3V) = 0.00333 M , remaining [HY] = 0.04 . pH = 4.7 + log (0.00333/0.04) = 4.7 - 1.08 = 3.62 .

Ref: NCERT Class 11 Chemistry > Chapter 6: Equilibrium > Topic: Physical Equilibrium - Solid-Liquid Gas-Liquid and Henry's Law

The ionization constant of a weak acid HA is 1.0 × 10⁻⁵ . What is the pH of a 0.1 M solution of this acid?

For HA H+ + A- , Ka = ([H+][A-]/[HA]) = (x²/0.1 - x) ≈ (x²/0.1) = 1.0 × 10⁻⁵ . Solving, x = sqrt1.0 × 10⁻⁶ = 1.0 × 10⁻³ , so pH = -log(1.0 × 10⁻³) = 3 .

Ref: NCERT Class 11 Chemistry > Chapter 6: Equilibrium > Topic: Ionic Equilibrium - Acids Bases and pH and Ionization of Weak Acids Bases