Question

A solution containing 10 g glucose has osmotic pressure 3.84 atm.If 10 g more glucose is added to same solution, what will be its osmotic pressure

Answer 1

The osmotic pressure of the solution on adding 10 more gram of glucose is 7.68 atm.

• The formula for osmotic pressure

is as follows :

π = MRT,   -(i)

where π denotes the osmotic pressure of a solution,

M denotes the molar concentration or molarity of the solution,

R denotes the gas constant,

and T denotes the temperautre of the solution.

• Given,

weight of glucose = 10 g

Osmotic pressure (π1) = 3.84 atm

Molecular formula of glucose = 180 g

Molar concentration of a solution is the number of moles of the solute present in one litre of the solution.

Therefore, molar concentration of glucose (M1) at π1 = number of moles of glucose (n) / 1 L

or, M1 = (10/180) moles/L

or, M1 = (1/18) moles/L

Therefore, substituting the values in (i), we get,

3.84 atm = (1/18) moles/L × R × T - (ii)

• Now, 10 g more glucose is added to the solution.

=> weight of glucose = (10 + 10) g = 20 g

=> M2 = (20/180) moles/L = (1/9) moles/L

=> π2 = (1/9) moles/L × R × T  -(iii)

• Dividing (ii) by (iii), we get,

π2 / 3.84 atm = (1/9) / (1/18)

=> π2 / 3.84 atm = (1×18)/9

=> π2 / 3.84 atm = 2

=> π2 = 2 × 3.84 atm

=> π2 = 7.68 atm