Q58 / 180 · KCET 2014 · Chemistry

\( 10 \mathrm{~g} \) of a mixture of \( \mathrm{BaO} \) and \( \mathrm{CaO} \) requires \( 100 \mathrm{~cm}^{3} \) of \( 2.5 \mathrm{M} \mathrm{HCl} \) to react completely. The
percentage of calcium oxide in the mixture is approximately
(Given : molar mass of \( \mathrm{BaO}=153 \) )

  • A
    \( 55.1 \)
  • B
    17.4
  • Correct answer
    C
    \( 52.6 \)
  • D
    14.9

Solution

For the completely neutralization reaction,
Let the mass of \( \mathrm{CaO} \) in mixture is \( x \mathrm{~g} \) and that of BaO is \( 10-x g \)
Now, The sum of the gram equivalents of \( \mathrm{CaO} \) and \( \mathrm{BaO} \)
\[ \begin{array}{l} =\frac{100 \times 2.5}{1000}=0.2 \\ \Rightarrow \frac{x}{28}+\frac{10-x}{76.5}=0.25 \\ \Rightarrow \frac{76.5 x+280-28 x}{28 \times 76.5}=0.25 \\ \Rightarrow 48.5 x=(0.25 \times 25 \times 76.5)-280 \\ \Rightarrow x=\frac{255.5}{48.5}=5.26 \end{array} \]
Percentage of \( \mathrm{CaO} \) in mixture is \( =\frac{5.26}{10} \times 100=52.6 \% \)

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

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