Question

The weight per cent of sucrose (formula weight $=342\,g \,mol ^{-1}$ ) in an aqueous solution is $3.42$. The density of the solution is $1 \,g \,mL ^{-1}$, the concentration of sucrose in the solution in $mol \, L ^{-1}$ is

• A. 0.01
• B. 0.1
• C. 1.0
• D. 10

Answer 1

Answer: (B)

Given,
Weight of sucrose $=\frac{3.42}{100}=0.0342\, g$
Molar mass of sucrose $=342 \,g$
Mass of solution $=100\, g$
Density of solution $=1 \,g\, mL ^{-1}$
$\therefore $ No. of moles of sucrose $=\frac{0.0342}{342}$
Also, density $=\frac{\text { Mass }}{\text { Volume }}$
$\therefore $ Volume $=\frac{100}{1}=100\, mL$
Concentration of solution is calculated in terms of molarity
Molarity $=\frac{\text { No. of moles of sucrose }}{\text { Vol. of solution in litres }} $
$=\frac{0.0342}{\frac{100}{1000}}=\frac{0.0342}{100} \times 1000=0.1 \,mol / L$