Question

The boiling points for aqueous solutions of sucrose and urea are the same at a constant temperature. If $3gm$ of urea is dissolved in its $1$ litre solution, what is the weight of sucrose dissolved in its $1$ litre solution?

[Urea $=60gm/mole$, sucrose $=342gm/mole$]

• A. $3.0gram$
• B. $17.1gram$
• C. $6.0gram$
• D. $34.2gram$

Answer 1

The correct option is B $17.1gram$

Given,

Boiling points of urea and sucrose are the same.

So, concentrations must be equal.

Molarity of urea$=$Molarity of surface.

$\frac{n_{urea}}{V}=\frac{n_{sucrose}}{V}$

$\frac{3}{60}=\frac{m}{342}$

$m=\frac{342}{20}=\frac{171}{10}$

$m=17.1grams$

Hence, $17.1grams$ of sucrose is needed.