Question

How many grams of methyl alcohol should be added to $10$ litre tank of water to prevent its freezing at $268$K?
($K_f$ for water is $1.86$ K kg $mo{l}^{-1}$)

• A. $899.04$ g
• B. $886.02$ g
• C. $860.2$ g
• D. $880.07$ g

Answer 1

Answer: (C)

$860.2$ g

Let us consider the equation:

$\Delta T_f=K_{f}m$

Where, $m$ is the molarity

$273-268=1.86\times \frac{w}{M\times V}$

$⟹5=1.86\times \frac{w}{32\times 10}$

$⟹w=\frac{5\times 32\times 10}{1.86}$

Hence, $w=860.2g$.

Hence, the correct option is $C$