Question

A solution of x moles of sucrose in 100 grams of water freezes at -$0.2^{\circ}C$ As ice separates the freezing point goes down to $0.25^{\circ}C$ How many grams of ice would have separated?

• A. 18 gram
• B. 20 gram
• C. 25 gram
• D. 23 gram

Answer 1

Answer: (B)

$\left(i\right)\Delta T_{f} =m \times K_{f}$
$0.2=\frac{X\times1000}{100} \times1.86$
$X=\frac{0.2}{10\times1.86}$
after freezing
$\Delta T_{f} =m\times K_{f}$
$\Delta T_{f} =\frac{X\times1000}{\left(100-y\right)}\times1.86$
$\Delta T _{f} =0.25$
On solving, Amount of ice y = 20 g ice