Question

Calculate the osmotic pressure of each of the following solutions at 290.0 K .

Part A

A 565.0 mL solution containing 85.0 g of glucose, C6H12O6 .

Part B

A 565.0 mL solution containing 125.0 g of magnesium sulfate, MgSO4 . (i = 1.3)

Answer 1

formula for osmatic pressure is

Pi = CRT

where C = concentration inmolarity

R = 0.0821L atm/mol-K

T = 290.0K

Part A

first find out the concentration

C = (weight/molar mass) x (1000/v in mL)

C = (85/180) x (1000 / 565 mL)

C = 0.836 M

Pi = CRT

Pi = 0.836 mol/L x0.0821 L-atm/mol-K x 290.0K

Pi = 19.9 atm

Part-B

first find out the concentration

C = (weight/molar mass) x (1000/v in mL)

C = (125/120.4) x (1000 / 565 mL)

C = 1.837 M

but actually MgSO4 can dissociatee in ti Mg2+ + So42-

so actual concentration = 2 x 1.837 = 3.674 mol/L

Pi = 3.674 mol/L x 0.0821 L-atm/mol-K x 290.0K

Pi = 87.5 atm