chemistry
posted by bf .
A 1.10 sample contains only glucose and sucrose . When the sample is dissolved in water to a total solution volume of 25.0 , the osmotic pressure of the solution is 3.78 at 298 .

A volume of 25.0 what? 3.78 what? 298 what? And what is the question?

A 1.10g sample contains only glucose and sucrose . When the sample is dissolved in water to a total solution volume of 25.0ML , the osmotic pressure of the solution is 3.78atm at 298K
a.What is the percent by mass of glucose in the sample?
b.What is the percent by mass of sucrose in the sample? 
I would do this but you must do the work. You must solve two simultaneous equation unless I've missed the boat.
Let X = grams glucose
and Y = grams sucrose.
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pi = osmotic pressure = MRT
You know pi, R, and T, solve for M
Molarity = moles x L
You know L, solve for moles.
Here are the two equations.
X + Y = 1.10
(X/molar mass glucose) + (Y/molar mass sucrose) = moles.
Solve for X and Y, then you can determine percent of each.
Post your work if you get stuck. 
22%