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

(a) Beaker L: Sodium chloride (NaCl) is a strong electrolyte. In aqueous solution, it dissociates completely into Na^+ and Cl^- ions. (Technically it also contains water molecules, but among the choices, it is the one characterized by full ionic dissociation).
(b) Beaker M: Distilled water is a non-electrolyte. While it undergoes self-ionization to a negligible extent, it is considered to consist almost entirely of H_2O molecules.
(c) Beaker K: Acetic acid (CH_3COOH) is an organic acid. All acids have a pH value less than 7.