Q55 / 180 · COMEDK 2020 · Chemistry

The volume of $10 \mathrm{~N}$ and $4 \mathrm{~N}$ HCl required to make 1 litre of $7 \mathrm{~N} \mathrm{HCl}$ are

  • A
    $0.75$ litre of $10 \mathrm{~N} \mathrm{HCl}$ and $0.25$ litre of $4 \mathrm{~N} \mathrm{HCl}$
  • B
    $0.80$ litre of $10 \mathrm{~N} \mathrm{HCl}$ and $0.20$ litre of $4 \mathrm{~N} \mathrm{HCl}$
  • C
    $0.60$ litre of $10 \mathrm{~N} \mathrm{HCl}$ and $0.40$ litre of $4 \mathrm{~N} \mathrm{HCl}$
  • Correct answer
    D
    $0.50$ litre of $10 \mathrm{~N} \mathrm{HCl}$ and $0.50$ litre of $4 \mathrm{~N} \mathrm{HCl}$

Solution

I et the volume of $10 \mathrm{~N} \mathrm{HCl}$ used is $x$ litre.- $\therefore$ The volume of $4 \mathrm{~N} \mathrm{HCl}$ used is $(1-x)$ litre. $$ \begin{aligned} &\therefore \quad 7=\frac{10 \times x+4 \times(10-x)}{1} \\ &\therefore \quad x=05 \mathrm{~L} \end{aligned} $$ $\therefore$ Volume of $10 \mathrm{~N} \mathrm{HCl}$ and $4 \mathrm{~N} \mathrm{HCl}$ used is $0.5 \mathrm{~L}$, each.

Hence, the correct answer is option: 'D'.

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