Practice question

Given: The K_a of formic acid ( HCOOH ) is 1.8 × 10⁻⁴. What is the pH of a 0.02 M solution? Formula: K_a = x²/0.02, 1.8 × 10⁻⁴= x²/0.02, x² = 3.6 × 10⁻⁶. Substitution & Calculation: x = √3.6 × 10⁻⁶approx 1.9 × 10⁻³, pH = -log(1.9 × 10⁻³) approx 2.72 . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.