Which among the following salts turns blue litmus red in its aqueous solution?

Step-by-step solution

To identify the salt that yields an acidic aqueous solution—thus turning blue litmus red—consider the hydrolysis behavior based on the strength of the parent acid and base. Option A, KCN , derives from a strong base (KOH) and weak acid (HCN). The cyanide ion hydrolyzes as CN ^- + H ₂ O HCN + OH ^- , producing hydroxide ions and resulting in a basic solution. Option B, Na ₂ CO ₃ , originates from a strong base (NaOH) and weak acid ( H ₂ CO ₃ ). The carbonate ion hydrolyzes via CO ₃²⁻ + H ₂ O HCO ₃^- + OH ^- , also y