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JEE Mains · Chemistry · STD 11 - 6.2. Equilibrium - II (icon Equilibrium)

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 \(.....\,g\) (Given \(pK _{ b }\left( NH _{3}\right)=4.74\); Molar mass of \(NH _{3}=17\,g\,mol ^{-}\) ; Molar mass of \(NH _{4} Cl =53.5\,g\,mol ^{-1}\) )

  1. A \(53.5\)
  2. B \(72.3\)
  3. C \(107\)
  4. D \(126\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(107\)

Step-by-step Solution

Detailed explanation

\(POH =14-8.26\) \(= pK _{ b }+\log \frac{\left[ NH _{4}^{+}\right]}{\left[ NH _{3}\right]}\) \(=5.74=4.74+\log \frac{\left[ NH _{4}^{+}\right]}{0.2} \Rightarrow\left[ NH _{4}^{+}\right]=2\) Hence,\(NH _{4} Cl =2 \times 53.5=107\,g\)
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