Question

When the following 1.0 mol dm\(^{-3}\) aqueous solutions are arranged in order of increasing pH, which is the correct order?

I. Ammonium chloride
II. Ammonium ethanoate
III. Sodium ethanoate

• A. I<II<III
• B. II<I<III
• C. III<I<II
• D. III<II<I

Hint:

Ammonium chloride is acidic due to the presence of ammonium ions. Sodium ethanoate, being a strong base, increases the pH more than ammonium ethanoate.

Answer 1

The Correct Option is A

Ammonium chloride (I) is the salt of a weak base (ammonium hydroxide) and a strong acid (hydrochloric acid). As a result, it dissociates in water to produce an acidic solution, which will have the lowest pH.

Ammonium ethanoate (II) is the salt of a weak acid (ethanoic acid) and a weak base (ammonium hydroxide). This salt will hydrolyze in water, but to a lesser extent than ammonium chloride, resulting in a more moderate pH compared to ammonium chloride.

Sodium ethanoate (III) is the salt of a strong base (sodium hydroxide) and a weak acid (ethanoic acid). This results in a basic solution because the sodium ion does not hydrolyze, while the ethanoate ion (acetate) can accept protons, making the solution more basic and leading to the highest pH.

Therefore, the correct order of pH is I < II < III.