A 1.112 g sample contains only vitamin C (C6H8O6) and sucralose (C12H19Cl3O8). When the sample is dissolved in water to a total volume of 28.6 mL, the osmotic pressure of the solution is 4.47 atm at 287 K. What is the mass percent of vitamin C and sucralose in the sample?

Answer 1

You have two unknowns so you will need two equations. I will set this up piece meal and let you put it together. Post your work if you run into trouble.
To save typing mm = molar mass
pi = osmotic pressure

Let X = grams vitamin C
and Y = grams sucralose
equation 1 is X + Y = 1.112 grams
equation 2 is pi for vit C + pi for sucralose = 4.47 atm.
Here is the put together part.
pi for vit C is iMRT = 1*(X/mm vit C/0.0286)*0.08206*287
pi for sucralose is iMRT = 1*(Y/mm suc/0.0286)*0.08206*287
So you have equation 1. Substitute pi for vit C and pi for suc into equation 2 and solve the two equations simultaneously for X and Y. Then
% Vitamin C = (grams X/1.112)*100 = ?
% Sucralose = (grams Y/1.112)*100 = ?