1. Tardigrade
  2. Question
  3. Chemistry
  4. The ionisation constant of an acid, Ka is the measure of strength of an acid. The Ka values of acetic acid, hypochlorous acid and formic acid are 1.74 × 10-5, 3.0 × 10-8 and 1.8 × 10-4 respectively. Which of the following orders of pH of 0.1 mol dm-3 solutions of these acids is correct?

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Q. The ionisation constant of an acid, Ka is the measure of strength of an acid. The Ka values of acetic acid, hypochlorous acid and formic acid are 1.74×10−5, 3.0×10−8 and 1.8×10−4 respectively. Which of the following orders of pH of 0.1moldm−3 solutions of these acids is correct?

Equilibrium

Solution:

Ka is a measure of the strength of the acid i.e., larger the value of Ka, the stronger is the acid.
Thus, the correct order of acidic strength is
HCOOH>CH3COOH>HClOKa:1.8×10−41.74×10−53.0×10−8
Stronger the acid, lesser will be the value of pH. Hence, the correct order of pH is HClO>CH3COOH>HCOOH