Question

70. If the mass percentage of methyl alcohol in aqueous 70
solution is 16% then molality of the solution will be
(1) 7.25 m
(2) 3.15 m2
(3) 8.23 m
(4) 5.95 m​

Answer 1

Answer:

5.95

Explanation:

molality = $\frac{number of moles of solute}{weight of solvent (kg)}$

16 % w/w solution contains 16 grams of solute in 100 grams of its aqueous solution

Therefore multiplying by 10 on denominator and numerator we have

160 grams of solute in 1000 grams of solution

so,its contains 840 grams of solvent =0.84 kg

Molecular wt of methyl alcohol=32

No: of moles = $\frac{weight}{molecular weight}$

∴ molality = $\frac{160}{0.84*32}$

=5.95 m