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JEE Main 2025 Chemistry question

ChemistryEquilibriumJEE Main 2025

One litre buffer solution was prepared by adding 0.10 mol each of NH₃ and NH₄Cl in deionised water. The change in pH on addition of 0.05 mol of HCl to the above solution is × 10⁻². (Nearest integer) Given : pKb of NH₃ = 4.745 and log₁₀3 = 0.477

Answer: 48

Solution

Initial pOH=pKb=4.745, pH=9.255. After adding HCl: NH3=0.05, NH4Cl=0.15, pOH=pKb+log(0.15/0.05)=5.222, pH=8.778. Change=0.477≈47.7×10⁻².

Question ID VK-003089