KVPY Sample Paper KVPY Stream-SX Model Paper-10

  • question_answer
    When a gas is bubbled through water at 298 K, a very dilute solution of the gas is obtained. Henry's law constant for the gas at 298 K is 100 kbar. If the gas exerts a partial pressure of 1 Bar, the number of millimoles of the gas dissolved in one litre of water is

    A) 0.555               

    B) 5.55

    C) 0.0555             

    D) 55.5

    Correct Answer: A

    Solution :

    \[{{\operatorname{K}}_{H}}=100kbar=1{{0}^{5}}bar,\]
    \[\operatorname{P}={{K}_{H}}\times {{x}_{A}}\]
    \[{{\operatorname{x}}_{A}}=\frac{P}{{{K}_{H}}}=\frac{1}{100\times 1{{0}^{3}}}=1{{0}^{-5}}\]
    Weight of water \[=1000\text{ }g\]
    Moles of water \[=\frac{1000}{18}=55.5\]
                            \[\left( \because 1\operatorname{mL}=1000g \right)\]
    Mole fraction \[=1{{0}^{-5}}=\frac{x}{55.5+x}\]
    As \[55.5>>>x,\]thus neglecting from denominator
    \[1{{0}^{-5}}=\frac{x}{55.5}\Rightarrow x=55.5\times 1{{0}^{-5}}\]Moles or \[~0.555\]millimoles.


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