Question

What would be the freezing point of aqueous solution containing $17\, g$ of $C _{2} H _{5} OH$ in $1000\, g$ of water?

• A. $0.34^{\circ} C$
• B. $0.0^{\circ} C$
• C. $-\,0.34^{\circ} C$
• D. $-\,0.69^{\circ} C$

Answer 1

Answer: (D)

$-\,0.69^{\circ} C$

Answer 2

Molality of $C _{2} H _{5} OH$ (non-electrolyte) solution
$=\frac{17 g / 46 \times 1000 g}{1000 g \text { water }}$
$=0.369$
$\Delta T_{f} =k_{f} \times m$
$=1.86 \times 0.369=0.686$
Freezing point of the solution
$=0^{\circ} C -0.686^{\circ} C$
$=-0.69^{\circ} C$