Q. The amount of urea dissolved in 500 cc of water ($K_{f} = 1.86℃$) to produce a depression of $0.186℃\$ in the freezing point is
A) 9 g
B) 6 g
C) 3 g
D) 0.3 g
Explanation
(c)
We know that,
w(mass of solute) = $\frac{m \times \mathrm{\Delta}T_{f} \times W}{1000 \times k_{f}}$
m= mol. wt. of urea (60)
$\mathrm{\Delta}T_{f} = 0.186℃$
$k_{f}$ =1.86${^\circ}$, W =500 g
= $\frac{60 \times 0.186 \times 500}{1000 \times 1.86}$
=3g
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.