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BCECE Engineering BCECE Engineering Solved Paper-2015

  • question_answer
    At\[\text{8}0{}^\circ \text{ C}\], the vapour pressure of pure liquid A is 520 mm Hg and that of pure liquid B is 1000 mm Hg. If a mixture solution of A and  B boils at \[\text{8}0{}^\circ \text{ C}\] and 1 atm pressure, the amount of A in the mixture is

    A) 50 mol per cent                

    B) 54 mol per cent

    C)  32 mol per cent               

    D) 44 mol percent

    Correct Answer: A

    Solution :

    Let the amount of 'A' in the mixture be \[{{\chi }_{A}}\] and B be \[{{\chi }_{B}}\] \[{{p}_{T}}=760={{p}^{\circ }}_{A}{{\chi }_{A}}+{{p}^{\circ }}_{B}{{\beta }_{B}}\] \[760=520{{\chi }_{A}}+1000(1-{{\chi }_{A}})\] \[480{{\chi }_{A}}=240\] \[{{\text{ }\!\!\chi\!\!\text{ }}_{\text{A}}}\text{=}\frac{\text{1}}{\text{2}}\text{or 50 mol}\] percent


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