Question

Which of the following aqueous solution has minimum freezing point?

• A. $0.01\, M\, NaCl$
• B. $0.005\, M\, NaCl$
• C. $0.1\, M \,NaCl$
• D. $0.01\, M\, Na_2SO_4$

Answer 1

Answer: (A)

$0.01\, M\, NaCl$

Answer 2

Solution will have highest freezing point if $\Delta T_{f}$ (depression in freezing point) value will be lowest $\Delta T_{f}= i K_{f} m$

where, $i$ =van't Hoff's factor, $K_{f}=$ molal depression constant, $m =$ molality of solution As $k_{f}$ is a constant quantity, so $\Delta T_{f}$ depends upon and only.

For $NaCl , NaCl\to Na ^{+}+ Cl ^{-} i=2$

For $Na _{2} SO _{4}, i=3$; For $C _{12} H _{22} O _{11}, i=1$
$\Delta T_{f}$ value is lowest for $0.01 \,M \,NaCl$, hence, it has highest freezing point.