Question

Calculate osmotic pressure of a solution of cane sugar (sucrose) if 342 gm is present in 1000 ml at ${27}^{\circ }C$.

• A. 3.45
• B. 24.6
• C. 54.6
• D. 6.04

Answer 1

The correct option is B 24.6

We need to find the osmotic pressure of sucrose.
Firstly, sucrose is $C_{12}{H}_{22}{O}_{11}$. The molecular mass comes out to be 342 u and so the molar mass if 342 gm.
Now, let’s apply our known formula for osmotic pressure
$\pi =C\ast R\ast T$
Here we C = number of moles of solute/Volume of solution in liters.
We are given 5 gm of solute is present in 100 mL.
Number of moles = Given weight/Molar weight $=\frac{342}{342}=1$ mole in 1000 mL
That means we have 1 mole in 1 L of solution.
So, C = 1
We know R = 0.082, T = 273 + 27 = 300 K
Using these we get, $\pi =1\ast 0.082\ast 300=24.6$