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  • What volume of strong monobasic acid of normality 10 is needed to prepare 1 L of a buffer solution of pH 9, using 1 mol of NH3 and as much of strong acid needed. (Kb&nbsp

What volume of strong monobasic acid of normality 10 is needed to prepare 1 L of a buffer solution of pH 9, using 1 mol of NH3 and as much of strong acid needed. (Kb for NH3 = 1.8 \times 10-5) (pKb = 4.7447)

Option: 1

64 mL


Option: 2

6.4 mL


Option: 3

36 mL


Option: 4

36 L


Answers (1)

best_answer

\begin{array}{l}{\mathrm{NH}_{4} \mathrm{Cl} \text { is a salt of } S_{A} / W_{B}} \\ {\text {[since } W_{B}\left(\mathrm{NH}_{3}\right) \text { is left and } \mathrm{NH}_{4} \mathrm{Cl} \text { is formed. So, a mixture }} \\ {\left.\text {of } W_{B} \text { and salt is formed, which is a basic buffer}\right]}\end{array}

                \mathrm{NH}_{3} \quad+\mathrm{HCl} \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}
Initial           1                                     
final          (1 - x)                                   x

\begin{aligned} \mathrm{pOH} &=14-9=5 \\ \mathrm{pOH} &=\mathrm{p} K_{b}+\mathrm\log ( \frac{salt}{base}) \\ 5 &=4.7447+\log (x / 1-x) \text { and } x=0.64 \\ N_{1} V_{1} &=0.64 \text { and } V_{1}=0.64 / 10=0.064 \mathrm{L}=64 \mathrm{\: mL} \end{aligned}

Therefore, option(1) is correct

Posted by

vishal kumar

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