Question

250 gram of D-Glucose solution contain 10.8% carbon by weight. Find molality of solution. [Report your answer to nearest value]

(1) 1.03 m

(2) 20.55

(3) 0.05

(4) 4.03

Answer 1

Correct option is (2) 20.55

Glucose ⇒ C₆H₁₂O₆ [GMM = 180]

Mass of carbon (in 250 gram solution) = \(\left[\frac{250 \times 10.8}{100}\right]\)

∴ 72 gram of carbon in total mass of glucose (180)

\(\frac{250 \times 10.8}{100}\) Gram carbon present in =  \(\frac{180}{72}\times\frac{250 \times 10.8}{100}\) = 67.5 gram

Mass of solvent = (250 - 67.5) = 182.5 gram

Molality = \(\left(\frac{67.5\times1000}{180 \times182.5}\right) = 20.55\)