How many grams of methyl alcohol should be added to 10 litre tank of water to prevent its freezing at 268 K ? (Kf for water is 1.86 K kg mol-1 )

Question

How many grams of methyl alcohol should be added to 10 litre tank of water to prevent its freezing at 268 K ? (Kf for water is 1.86 K kg mol-1 ) (A) 880.07 g (B) 899.04 g (C) 886.02 g (D) 868.06 g

Tardigrade Admin · Accepted Answer

Δ Tf =Kf m where m = molality 273 - 268= 1.86 x (w/M× V) 5=1.86 ×(w/32×10) W=(5×32×10/1.86) =860.2 ≈ 868.06 g

Q. How many grams of methyl alcohol should be added to $10$ litre tank of water to prevent its freezing at $268 K$ ? $(K_{f} f or w a t er i s 1.86 K k g m o l^{- 1})$

880.07 g

899.04 g

886.02 g

868.06 g

$Δ T_{f} = K_{f} m$
where m = molality
273 - 268= 1.86 x $\frac{w}{M \times V}$
$5 = 1.86 \times \frac{w}{32 \times 10}$
$W = \frac{5 \times 32 \times 10}{1.86}$
$= 860.2 \approx 868.06 g$

Q. How many grams of methyl alcohol should be added to 10 litre tank of water to prevent its freezing at 268K ? (Kf​forwateris1.86Kkgmol−1)