Question

$K_f$ for water is$1.86Kkg{mol}^{-1}$. If your automobile radiator holds 1.0 kg of water ,how many grams of ethylene glycol $\left(C_2{H}_6{O}_2\right)$ must you add to get the freezing point of the solution lowered to $-2.8^{o}C$?

• A. 72 g
• B. 93 g
• C. 39 g
• D. 27 g

Answer 1

The correct option is B 93 g

Here $\Delta T_f=0-(-{2.8}^{o}C)=2.8$

$\because \Delta T_f=K_f\frac{W}{M_1\times W_2}$

$\therefore 2.8=1.86\times \frac{W}{62\times 1}$

$\Rightarrow W=93.33\approx 93g$

Hence, the correct option is $B$