Question

The density of a $3M$ sodium thiosulphate $(N{a}_2{S}_2{O}_3)$ solution is $1.25g/mL$ . Calculate the percent by weight of sodium thiosulphate

• A. $12.64\%$
• B. $37.92\%$
• C. $0.87\%$
• D. $63.21\%$

Answer 1

Answer: (B)

Molecular weight of
$N{a}_2{S}_2{O}_3=2\times 23+2\times 32+3\times 16$
$=158$
From molarity
$=\frac{\%\text{ by weight of solute × density of solution ×10}}{M}$
$3=\frac{\%\text{by weight of}N{a}_2{S}_2{O}_3\times 1.25\times 10}{158}$
$\therefore \%$ by weight of $N{a}_2{S}_2{O}_3$
$=\frac{3\times 158}{1.25\times 10}$
$=37.92\%$