JEE Main & Advanced JEE Main Paper (Held On 15 April 2018) Slot-II

  • question_answer
    Following four solutions are prepared by mixing different volumes of NaOH and HCl of different concentrations, pH of which one of them will be equal to 1?                                               [JEE Online 15-04-2018 (II)]

    A) \[55mL\frac{M}{10}HCl+45mL\frac{M}{10}NaOH\]

    B) \[75mL\frac{M}{5}HCl+25mL\frac{M}{5}NaOH\]

    C) \[\text{100mL}\frac{\text{M}}{\text{10}}\text{HCl+100mL}\frac{\text{M}}{\text{10}}\text{NaOH}\]

    D) \[\text{60mL}\frac{M}{10}HCl+40mL\frac{M}{10}NaOH\]

    Correct Answer: B

    Solution :

    \[75mL\frac{M}{5}HCl+25mL\frac{M}{5}NaOH\] \[25mL\frac{M}{5}NaOH\] will neutralise \[25mL\frac{M}{5}HCl\] \[75-25=50mL\frac{M}{5}HCl\] will remain. Total volume will be \[75+25=100mL.\] \[[{{H}^{+}}]=[HCl]=\frac{M}{5}\times \frac{50}{100}=\frac{M}{10}\] \[pH=-{{\log }_{10}}[{{H}^{+}}]=-{{\log }_{10}}\frac{M}{10}=1\]


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