Question

X and Y are two compounds of elements A and Cl. Molar mass and mass % of Cl are given in the table below.
$\begin{array}{ccc}\text{Compound}& \text{Molar mass}& \%\text{of Cl}\\ X& 137& 77.5\\ Y& 208& 85.1\end{array}$

Thus, X and Y are:

• A. $AC{l}_3,AC{l}_4$
• B. $A_{2}C{l}_3,AC{l}_3$
• C. $ACl,AC{l}_2$
• D. $AC{l}_3,AC{l}_5$

Answer 1

The correct option is D $AC{l}_3,AC{l}_5$

Let, X be $AC{l}_x\leftrightharpoons A^{x+}+xC{l}^{-},$
Y be $AC{l}_y\leftrightharpoons A^{y+}+yC{l}^{-}$
Molar mass of $X=137\text{g/mol}$
molar mass of $Y=208\text{g/mol}$
% of $Cl$ in $X=\frac{35.5x}{137}=\frac{77.5}{100}$
on solving, $x\approx 3.0$
% of $Cl$ in $Y=\frac{35.5y}{208}=\frac{85.1}{100}$
on solving, $y\approx 5$
Thus, $X$ is $AC{l}_{3}andY$ is $AC{l}_5$