Question

Which of the following is a weak electrolyte in aqueous solution

1.) sulfuric acid, H₂SO₄
2.) sodium hydroxide, NaOH
3.) potassium phosphate, K₃PO₄
4.) sucrose, C₁₂H₂₂O₁₁
5.) nitrous acid, HNO₂

Answer 1

Nitrous acid (HNO₂) is the weak electrolyte in aqueous solution because it ionizes to a limited extent, with a majority existing as intact molecules rather than ions. Potassium phosphate (K₃PO₄), however, is a strong electrolyte and fully dissociates in water.

Step-by-step explanation:

Nitrous acid (HNO₂) is a weak electrolyte in aqueous solution. When dissolved in water, it ionizes to a limited extent into hydrogen ions (H+) and nitrite ions (NO₂⁻), with the equilibrium consisting predominantly of undissociated nitrous acid molecules. That is to say, only about 5% of the nitrous acid exists as ions in an aqueous solution. In contrast, potassium phosphate (K₃PO₄) is considered a strong electrolyte because it dissociates completely into potassium ions (K+) and phosphate ions (PO₄³⁻) in solution.

Considering the extent of ionization, nitrous acid (HNO₂) should be regarded as the weak electrolyte between the two choices provided. Reactions involving a weak acid or base, such as nitrous acid, do not typically result in a neutral solution and the weak acid itself should be written as a molecule in a net ionic equation due to its limited ionization.