Question

Chloride samples are prepared for analysis by using $NaCl,KCl$ and $N{H}_{4}Cl$ separately or as mixtures. If $x$ mL is minimum volume of a $5.0\%$ by weight, $AgN{O}_3$ solution (density $=1.04$ g/cc) must be added to a sample weighing $0.3$ g in order to ensure complete precipitation of chloride in every possible cases, then the value of $100x$ is :

• A. $1833$
• B. $1800$
• C. $1850$
• D. none of the above

Answer 1

Answer: (A)

$1833$

Normality of $AgN{O}_3$ $=\frac{W_2\times 1000}{Ew\times V_{sol}\left(inmL\right)}$ $=\%$ by weight $\times 10\times \frac{d}{Ew}$ $=5\times 10\times \frac{1.04}{170}=0.3059N$
Of the three salts, $KCl,NaCl$ and $N{H}_{4}Cl,N{H}_{4}Cl$ has the maximum number of milli-equivalents which is $\frac{0.3}{53.5}\times 1000=5.607$

Therefore, the minimum volume required for complete precipitate is given below:
$N_1{V}_1=N_2{V}_2$ (meq. of $N{H}_{4}Cl$)

$0.3059\times V_1=5.607$

$\therefore V_1=\frac{5.607}{0.3059}=18.33$ mL