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Percentage Composition

4.0 g of a mi...

Question

4.0 g of a mixture of $N a C l$ and an unknown metal iodide $M I_{2}$ was dissolved in a water to form its aqueous solution. To this aqueous solution, The aqueous solution $A g N O_{3}$ was added gradually so that silver halides are precipitated. The precipitates were weighed at regular interval and the given curve for the mass of precipitate versus volume of $A g N O_{3}$ added was obtained. With the knowledge of the fact that halides are precipitated successively i.e. when one halide is precipitating , the other halide remains in the solution, answer the following questions:
(Molar mass of $A g = 108, I = 127, N a = 23$ ).
Points $P$ and $Q$ are: $P (20, 4.8), Q (37, 7.25)$
What is the approximate mass percentage of $M I_{2}$ ?

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Solution

The correct option is D 75
Mass of $A g C l$ (formed in $2^{nd}$ step $)$
$= 7.25 - 4.80 = 2.45 g$
$∵ 143.5 g A g C l$ form $58.5 g$ Nacl
2.45 g $A g C l$ form $\frac{58.5}{143.5} \times 2.45$
$= 1.0 g N a C l$
Mass of $M I_{2} = 4 - 1 = 3 g$
$\begin{matrix} % of M I_{2} & = \frac{3}{4} \times 200 = 75 % \end{matrix}$
$∴$ (D) is correct coption.

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The correct option is D 75Mass of AgCl (formed in 2nd step )=7.25−4.80=2.45 g∵143.5 gAgCl form 58.5 g Nacl2.45 g AgCl form 58.5143.5×2.45=1.0 gNaClMass of MI2=4−1=3g% of MI2=34×200=75%∴ (D) is correct coption.