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JEE Main Chemistry question

ChemistryEquilibriumJEE Main

The composition of an acidic buffer mixture made up of HA and NaA of total molarity 0.29 having pH=4.4 and Ka=1.8×10⁻⁵ in terms of concentration of salt and acid respectively is:

Answer: (A)

Solution

pKa=4.745. log([A⁻]/[HA])=4.4−4.745=−0.345→ratio=0.452. Solving with [A⁻]+[HA]=0.29 gives [A⁻]≈0.09 M, [HA]≈0.20 M.

Question ID VK-136303