MHTCET 11 Apr 2026 Shift 1 Paper

Concept:The pH of a salt solution depends on the relative strength of the acid and base from which the salt is derived.Explanation:A salt of a strong acid and a strong base gives a neutral solution with $pH = 7$.A salt of a strong base and a weak acid gives a basic solution with $pH > 7$.A salt of a weak base and a strong acid gives an acidic solution with $pH < 7$.A salt of a weak acid and a weak base is nearly neutral if the acid and base strengths are similar.Now analyse each option.$\mathrm{KNO}_{3}$ is formed from $\mathrm{KOH}$ (strong base) and $\mathrm{HNO}_{3}$ (strong acid), so its solution is neutral with $pH = 7$.$\mathrm{Na}_{2}\mathrm{CO}_{3}$ is formed from $\mathrm{NaOH}$ (strong base) and $\mathrm{H}_{2}\mathrm{CO}_{3}$ (weak acid), so its solution is basic with $pH > 7$.$\mathrm{CH}_{3}\mathrm{COONH}_{4}$ is formed from $\mathrm{CH}_{3}\mathrm{COOH}$ (weak acid) and $\mathrm{NH}_{4}\mathrm{OH}$ (weak base). Since $K_a$ of acetic acid and $K_b$ of ammonium hydroxide are nearly equal, its solution is approximately neutral with $pH \approx 7$.$\mathrm{CuCl}_{2}$ is formed from $\mathrm{Cu}(\mathrm{OH})_{2}$ (weak base) and $\mathrm{HCl}$ (strong acid). The cation $\mathrm{Cu}^{2+}$ undergoes hydrolysis to produce $\mathrm{H}^{+}$ ions, making the solution acidic with $pH < 7$.Therefore, the salt with $pH < 7$ at 298 K is $\mathrm{CuCl}_{2}$.Answer:$\mathrm{CuCl}_{2}$ (Option D)