A 1.084 g sample contains only vitamin C (C6H8O6) and sucralose (C12H19Cl3O8).

Question

When the sample is dissolved in water to a total volume of 37.4 mL, the osmotic pressure of the solution is 3.41 atm at 293 K. What is the mass percent of vitamin C and sucralose in the sample?

Answer 1

mass Vit C = X g

mass Suc = 1.084 g - X g

osmotic pressure = π = iMRT where i = van't Hoff factor; M = molarity; R = gas constant; T = temp in Kelvin

For VC:

i = 1; M = X g/176 g /0.0374 L; R = 0.0821 Latm/Kmol; T = 293K

For Suc:

i = 1; M = 1.084 g - X g / 398 g / 0.0374 L; R = 0.0821 Latm/Kmol; T = 293K

Total for both:

3.41 = (X/176 * 0.0374)(0.0821)(293) + (1.084 - X /398 * 0.0374)(0.0821)(293)

3.41 = (24.06 X / 6.58) + (26.08 - 24.06 X / 14.89)

3.41 = 3.66 X + 1.75 - 1.62 X

2.04 X = 1.66

X = 0.814 g = mass of Vitamin C

1.084 g - 0.814 g = 0.27 g = mass of Sucralose

Mass % Vitamin C = 0.814 g / 1.084 g (x100%) = 75.1%

Mass % Sucralose = 0.27 g / 1.084 g (x100%) = 24.9%