Question

Exactly 100 grams of a saturated solution of sucrose in water was determined to contain 67.98 grams of sucrose, C₁₂H₂₂O₁₁. Calculate the osmotic pressure of this solution at 25 C, if the density of the solution is 1.34 grams/ml.

Answer 1

Molar mass of C12H22O11,

MM = 12*MM(C) + 22*MM(H) + 11*MM(O)

= 12*12.01 + 22*1.008 + 11*16.0

= 342.296 g/mol

mass(C12H22O11)= 67.98 g

number of mol of C12H22O11,

n = mass of C12H22O11/molar mass of C12H22O11

=(67.98 g)/(342.296 g/mol)

= 0.1986 mol

use:

density = mass / volume to find volume of solution

volume of solution , V = mass/ density

= 100 g / 1.34 g/mL

= 74.6 mL

= 7.46*10^-2 L

Molarity,

C = number of mol / volume in L

= 0.1986/7.46*10^-2

= 2.662 M

T= 25 oC

= (25+273) K

= 298 K

use:

P = C*R*T

P = 2.662*0.0821*298

P = 65.1 atm

Answer: 65.1 atm