Question

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

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

Answer 1

Answer: (C)

Let, mass of $CaO=xg$
$\therefore$ Mass of $BaO=(10-x)g$
Again, $\because$ equivalent mass of BaO
$=\frac{\text{ molar mass }}{2}=\frac{153}{2}=76.5$
$\therefore$ Number of moles of $BaO=\frac{10-x}{76.5}$
and $\because$ equivalent mass of $CaO=\frac{56}{2}=28$
$\therefore$ Number of moles of $CaO=\frac{X}{28}$
From molarity $=\frac{\text{ moles of solute }}{\text{ volume of solution (in L) }}$
$2.5=\frac{\text{ moles of solute }}{\frac{100}{1000}}$
$\therefore$ Moles of solute $=\frac{2.5\times 100}{1000}$
or $\frac{x}{28}+\frac{10-x}{76.5}=0.25$
or $76.5x+28(10-x)=0.25\times 28\times 76.5$
or $48.5x=255.5$
or $x=\frac{255.5}{48.5}=5.26$
$\therefore \%$ of $CaO=\frac{5.26}{10}\times 100=52.6\%$