Chemistry Objective Questions A weak acid is one which is . (A) is not corrosive (B) is slightly ionized in water (C) does not produce salts with alkalis (D) does not conduct electric current in aqueous solution

A chemical property describes how a substance reacts with other substances or changes its chemical composition. For acids, these properties include reactions with metals, bases, carbonates, and certain salts.

• (A) Evolution of ammonia gas when heated with ammonium salt: Acids generally do not react with ammonium salts to evolve ammonia gas. This reaction is characteristic of bases reacting with ammonium salts (e.g., $\text{NaOH} + \text{NH}_4\text{Cl} \xrightarrow{\text{heat}} \text{NaCl} + \text{H}_2\text{O} + \text{NH}_3$). Therefore, this is not a chemical property of an acid.

• (B) Evolution of $\text{CO}_2$ gas when added to a trioxocarbonate (IV) salt: Acids react with carbonates (trioxocarbonate (IV) salts) to produce carbon dioxide gas, water, and a salt. For example, $\text{CaCO}_3(s) + 2\text{HCl}(aq) \rightarrow \text{CaCl}_2(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$. This is a chemical property of an acid.

• (C) Formation of salt and water with alkalis: Acids react with alkalis (bases) in a neutralization reaction to form salt and water. For example, $\text{HCl}(aq) + \text{NaOH}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l)$. This is a chemical property of an acid.

• (D) Formation of salt and hydrogen gas with reactive metal: Acids react with metals that are more reactive than hydrogen to produce a salt and hydrogen gas. For example, $\text{Zn}(s) + 2\text{HCl}(aq) \rightarrow \text{ZnCl}_2(aq) + \text{H}_2(g)$. This is a chemical property of an acid.

Based on the analysis, the evolution of ammonia gas when heated with an ammonium salt is a property of bases, not acids.

The final answer is $\boxed{\text{A}}$