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

Identifying salts that yield basic solutions depends on hydrolysis behavior. Salts formed from strong bases and weak acids produce basic solutions through anion hydrolysis, turning red litmus blue.

Sodium acetate ($\mathrm{CH}_3\mathrm{COONa}$) derives from sodium hydroxide (strong base) and acetic acid (weak acid). Its acetate ion hydrolyzes:
$\mathrm{CH}_3\mathrm{COO}^- (aq) + \mathrm{H}_2\mathrm{O} (l) \rightleftharpoons \mathrm{CH}_3\mathrm{COOH} (aq) + \mathrm{OH}^- (aq)$
generating hydroxide ions and a basic solution.

Copper(II) chloride ($\mathrm{CuCl}_2$), from copper(II) hydroxide (weak base) and hydrochloric acid (strong acid), hydrolyzes to produce hydrogen ions, yielding an acidic solution. Potassium chloride ($\mathrm{KCl}$), from strong base and strong acid, undergoes negligible hydrolysis, resulting in a neutral solution.

Only sodium acetate produces the basic solution required to turn red litmus blue.