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JEE Main 20199 JanuaryMorning Shift
Exam
JEE Main
Year
2019
Date
9 January
Shift
Morning Shift
Subject
Chemistry
Chapter
Ionic Equilibrium

JEE Main 2019 · 9 January · Morning Shift · Chemistry · Ionic Equilibrium

20ml of 0.1 M H_ 2 SO _ 4 solution is added to 30mL of 0 .2 M NH _...

20ml of {\text{0.1 M H}_{2}{SO}_{4} solution is added to 30mLof0.2MNH4OH30mL of 0 .2 M{NH}_{4}OH solution. The pHpH of the resultant mixture is: \left[{pk}_{b}of{NH}_{4}OH = 4 .7\right]20ml of 0.1 M H_ 2 SO _ 4 solution is added to 30mL of 0 .2 M NH _ 4 OH solution. The pH of the resultant mixture is: [

Options

  1. A5.05.0
  2. B5.25.2
  3. C9.49.4
  4. D9.09.0

Correct answer

D. 9.09.0

Step-by-step solution

Millimoles of H2SO4=20×0.1=2{H}_{2}S{O}_{4} = 20 \times 0.1 = 2

Millimoles of NH4OH=30×0.2=6N{H}_{4}OH = 30 \times 0.2 = 6

20ml of 0.1 M H_ 2 SO _ 4 solution is added to 30mL of 0 .2 M NH _ 4 OH solution. The pH of the resultant mixture is: [

Hence, the solution will act as a basic buffer.

pOH=pKb+log[salt][Base]pOH = p{K}_{b} + log\dfrac{\left[salt\right]}{\left[Base\right]}

\left[N{H}_{4}^{+}\right] = 2 \times \left[{\left(N{H}_{4}\right)}_{2}S{O}_{4}\right]; {\left[N{H}_{4}\right]}^{+} = 4<br/><br/><br /><br />pOH = p{K}_{b} + log\dfrac{\left[N{H}_{4}^{+}\right]}{\left[N{H}_{3}\right]}<br/><br/><br /><br />= 4.7 + log\dfrac{4}{2}<br/><br/><br /><br />= 4.7 + 0.3010 = 5.010<br/><br/><br /><br />pH = 14 - pOH = 9

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