Question

Molality of pure ethyl alcohol (density
0.92 g/ml) is
1) 15 m
2) 92 m
4) 20 m
inntinn nf 99% H Swy)
3) 46
please explain​

Answer 1

Answer:

answer is 15m..

Explanation:

Molality of a solution is defined as no. of moles of solute per Kg of solvent. It's temperature independent. If we are talking about pure ethanol (C2H5OH), that means there's no water or any other compound present except ethanol viz 100% ethanol.

Molality = (moles of solute)/(weight of solvent in Kg)

Also, no. of moles = (weight in grams)/ (molecular weight)

& 1 Kg = 1000 gms

So substituting these things,

m = [(wt. of ethanol)/(molecular weight of ethanol)] × [1000/(wt. of ethanol)]

m = [1/(molecular weight of ethanol)] × 1000

Molecular weight of ethanol is 12×2 + 1×5 + 16×1 + 1×1

=> 46 amu

m = 1000/46 = 21.7391

m = 21.7391