Question

The pH value of a solution determines whether it is acidic, basic or neutral in nature. 

1. The concentration of hydrogen ion in the sample of a soft drink is 3.8 × 10^-3 mol/L. Calculate its pH. Also predict whether the above solution is acidic, basic or neutral.

2. The dissociation constants of formic acid (HCOOH) and acetic acid (CH₃COOH) are 1.8 × 10^-4 and 1.8 × 10^-4 respectively. Which is relatively more acidic? Justify your answer.

Answer 1

1. pH = – log[H⁺] = – log[3.8 × 10^-3] = 2.42 Since pH is less than 7, it is an acidic solution,

2. HCOOH is more acidic.

K_a value is directly proportional to the acid strength, i.e., greater the K_a value, stronger is the acid.