Question

K, L and M are beakers containing three different solutions: [Beaker K: Aqueous acetic acid, Beaker L: Sodium chloride solution, Beaker M: Distilled water]. Name the beaker which: 
(a) contains only ions. 
(b) contains only molecules. 
(c) has pH less than 7. 

 

Hint:

Aqueous acetic acid is a weak electrolyte, meaning it contains both ions and molecules, as it only partially dissociates in water!

Answer 1

We are given:

Beaker K = Aqueous acetic acid
Beaker L = Sodium chloride solution
Beaker M = Distilled water

Let us identify each one carefully.

(a) Beaker which contains only ions:
Beaker L
Sodium chloride solution is a solution of a strong electrolyte.
In water, sodium chloride dissociates completely into Na⁺ and Cl^- ions.
Therefore, it is considered to contain only ions.

(b) Beaker which contains only molecules:
Beaker M
Distilled water consists of only water molecules and practically no ions.
Therefore, the beaker containing only molecules is M.

(c) Beaker which has pH less than 7:
Beaker K
Aqueous acetic acid is an acidic solution.
Acids have pH less than 7.
Hence, the beaker with pH less than 7 is K.

Detailed Note:
- Aqueous acetic acid is a weak acid, so it contains both molecules and some ions, and its pH is less than 7.
- Sodium chloride solution is neutral and contains ions in solution.
- Distilled water is neutral and contains only molecules.

Final Answers:
(a) L
(b) M
(c) K