AP EAMCET202022 Sep 2020Evening ShiftChemistryIonic EquilibriumActual
Weak acids are partially ionised in aqueous solutions. The ionisation constants of some acids are given below. Arrange these acids in increasing order of their acid strength array cll Index & 1 c Acid & 1 c array c Ionisation constant array 1 & Formic acid ( HCOOH ) & 1.8 10⁻⁴ 2 & Hypochlorous acid ( HClO ) & 3.0 10⁻⁸ 3 & Nitrous acid ( HNO ₂ ) & 4.5 10⁻⁴ 4 & Hydrocyanic acid ( HCN ) & 4.9 10⁻¹⁰ array
Options
- A4 < 2 < 1 < 3
- B1 < 2 < 3 < 4
- C2 < 3 < 1 < 4
- D4 < 3 < 2 < 1
Correct answer
A. 4 < 2 < 1 < 3
Step-by-step solution
The relative strengths of acids may be determined by measuring their equilibrium constants in aqueous solutions. Stronger acids ionise to a greater extent. The larger the K_a , of an acid, the larger the concentration of H ₃ O ⁺ and A⁻ relative to the concentration of the non-ionised acid, H A . Thus, a stronger acid has a larger ionisation constant than does a weaker acid. The ionisation constants increase as the strengths of the acids increase and hence, the correct option is (1).