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← JEE Main 2022 · 26 Jul · Shift 2
ChemistrySingle correct+4 / -1Question 63 of 90

JEE Main 2022 · 26 Jul · Shift 2, Chemistry question 63

Class XII students were asked to prepare one litre of buffer solution of pH 8.26 by their Chemistry teacher. The amount of ammonium chloride to be dissolved by the student in 0.2 M ammonia solution to make one litre of the buffer is

(Given: pKb(NH3)=4.74\mathrm pK_b(\mathrm{NH_3})=4.74; Molar mass of NH3\mathrm{NH_3} = 17 g mol−1^{-1}; Molar mass of NH4Cl\mathrm{NH_4Cl} = 53.5 g mol−1^{-1})

Choose one option
Answer and worked solution

Official answer: C

Basic buffer. pOH =14−8.26=5.74=4.74+log⁡[NH4+][NH3]=14-8.26=5.74=4.74+\log\frac{[\mathrm{NH_4^+}]}{[\mathrm{NH_3}]}, so the ratio is 10 and [NH4Cl]=2[\mathrm{NH_4Cl}]=2 M.

Mass 2×53.5=107.02\times53.5=107.0 g in one litre.

(C)