Question

$10g$ of a mixture of $BaO$ and $CaO$ requires $100cm^{3}$ of $2.5MHCl$ to react completely. The percentage of calcium oxide in the mixture is approximately.
(Given, molar mass of $BaO=153$ )

• A. $52.6$
• B. $55.1$
• C. $44.9$
• D. $47.4$

Answer 1

Answer: (A)

Let, mass $CaO=xg$
$\therefore $ Mass of $BaO=\left(10 - x\right)g$
Again, equivalent mass of $BaO$
$=\frac{\text{ molar mass }}{2}=\frac{153}{2}=76.5$
$\therefore $ Number of mol of $BaO\frac{10 - x}{76 . 5}$
and equivalent mass of $CaO=\frac{56}{2}=28$
$\therefore $ Number of mol of $CaO=\frac{x}{28}$
$\therefore $ Moles of solute $=\frac{25 \times 100}{1000}=0.25$
$\therefore $ For complete neutralisation (reaction) moles of $BaO$ and $CaO=$ moles of $HCl$ (solute)
$\therefore \frac{x}{28}+\frac{10 - x}{76 . 5}=0.25$
or $76.5x+28\left(\right.10-x\left.\right)=0.25\times 28\times 76.5$
or $48.5x=255.5$
or $x=\frac{255 . 5}{48 . 5}=5.26$
$\therefore $ $\%$ of $CaO=\frac{5 . 26}{10}\times 100=52.6\%$