2. Sample Papers
  3. KVPY

KVPY Sample Paper KVPY Stream-SX Model Paper-13

  • question_answer
    20 mL of \[\text{0}\text{.1M}\,{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\] solution is added to 30 mL of \[\text{0}\text{.2}\,\text{M}\,\text{N}{{\text{H}}_{\text{4}}}\text{OH}\] solution. The pH of the resultant mixture is: \[\text{ }\!\![\!\!\text{ p}{{\text{K}}_{\text{b}}}\,\text{of}\,\text{N}{{\text{H}}_{\text{4}}}\text{OH=4}\text{.7 }\!\!]\!\!\text{ }\]

    A) 9.4

    B) 5.02

    C) 9.0

    D) 5.2

    Correct Answer: C

    Solution :

    20 ml 0.1 M \[{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\]\[\Rightarrow \] \[{{\eta }_{{{H}^{\,+}}\,}}=\,\,4\]
    30 ml 0.2 M \[\text{N}{{\text{H}}_{\text{4}}}\text{OH}\]\[\Rightarrow \] \[{{\eta }_{N{{H}_{4}}OH}}=\,6\]
    \[\text{N}{{\text{H}}_{4}}\text{OH}+{{\text{H}}^{+}}\,\,\text{NH}_{4}^{\oplus }+{{\text{H}}_{2}}\text{O}\]
    \[\begin{align}   & \Rightarrow 6\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,4\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0 \\  & \Rightarrow 6\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,4\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,0 \\ \end{align}\]
    Solution is basic buffer
    \[\text{pOH}\,=\,\text{P}{{k}_{b}}\,+\text{log}\frac{\text{NH}_{\,4}^{\,+}}{\text{N}{{\text{H}}_{4}}\text{OH}}\]
    \[=\,4.7+\text{log}2\,=\,4.7+0.3\,=\,5\]
    \[\text{PH}\,=\,14\,-\,5\,=\,9\]


You need to login to perform this action.
You will be redirected in 3 sec spinner