Question

250 g solution of D-glucose in water contains 10.8% of carbon by weight. The molality of the solution is nearest to ______.

(Given: Atomic weights are H, 1u; C, 12u; O, 16u)

Options

• 1.03

• 2.06

• 3.09

• 5.40

Answer 1

250 g solution of D-glucose in water contains 10.8% of carbon by weight. The molality of the solution is nearest to 2.06.

Explanation:

\[\ce{C6H12O6 -> Glucose}\]

We know, `"mass of C"/"mass of glucose" = 72/180`

Given: % of C = 10.8 = `"mass of C"/"mass of solution" xx 100`

`(10.8 xx 250)/100` = mass of C

⇒ Mass of C = 27 gm

∴ mass of glucose = 67.5 gm

∴ moles of glucose = 0.375 moles

Mass of solvent = 250 − 67.5 gm = 182.5 gm

∴ Molality = `0.375/0.1825` = 2.055 ≈ 2.06