Select the basic salt. ? NH?Br ? NaBr ? RbCl ? NaCN ? KBr
The Correct Answer and Explanation is:
The correct answer is NaCN.
A salt is considered basic if it dissolves in water to produce a solution with a pH greater than 7. This occurs when the salt is formed from a strong base and a weak acid. The character of a salt is determined by the properties of its constituent ions, specifically their ability to react with water in a process called hydrolysis.
Let’s analyze each option:
- NH₄Br (Ammonium Bromide): This salt is formed from a weak base, ammonia (NH₃), and a strong acid, hydrobromic acid (HBr). When dissolved in water, the ammonium ion (NH₄⁺) acts as an acid by donating a proton to water, producing hydronium ions (H₃O⁺) and making the solution acidic. The bromide ion (Br⁻) is the conjugate base of a strong acid, so it does not react with water. The overall result is an acidic solution.
- NaBr (Sodium Bromide): This salt is formed from a strong base, sodium hydroxide (NaOH), and a strong acid, hydrobromic acid (HBr). Neither the sodium ion (Na⁺) nor the bromide ion (Br⁻) undergoes significant hydrolysis. They are spectator ions. Therefore, a solution of NaBr is neutral, with a pH of approximately 7.
- RbCl (Rubidium Chloride): This salt is formed from a strong base, rubidium hydroxide (RbOH), and a strong acid, hydrochloric acid (HCl). Similar to NaBr, neither the rubidium ion (Rb⁺) nor the chloride ion (Cl⁻) hydrolyzes in water. This results in a neutral solution.
- NaCN (Sodium Cyanide): This salt is formed from a strong base, sodium hydroxide (NaOH), and a weak acid, hydrocyanic acid (HCN). In solution, the sodium ion (Na⁺) is a neutral spectator ion. However, the cyanide ion (CN⁻) is the conjugate base of a weak acid. It reacts with water by accepting a proton, which produces hydroxide ions (OH⁻). This reaction, CN⁻ + H₂O ⇌ HCN + OH⁻, increases the concentration of OH⁻ in the solution, making it basic.
Therefore, among the choices provided, NaCN is the only salt that will form a basic solution upon dissolving in water
