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2. Colligative properties of solutions of electrolytes. Isotonic coefficient.
3. Ebullioscopy and cryoscopy.
4. Study of the colligative properties of biological fluids as important char-
acteristics of the state of the organism. The role of osmotic pressure in biologi-
cal systems.
5. Isotonic, hyper- and hypotonic solutions and their application in medicine.
6. Osmolality and osmolarity of biological fluids.
The output test-control on the themes «Buffer systems» and «Colligative
properties».
Homework exercises.
1. Calculate the vapor pressure of water over a solution containing 45 g
of glucose (C
6
H
12
O
6
) in 720 ml of water at 25
0
C. The water vapor pressure at
25 °C is 3168 Pa.
Answer
: 3148 Pa.
2. Determine the molar mass of the non-electrolyte if its mass fraction in the
solution is 1.96% and the solution freezes at –0.2480 °C.
Answer
: 150.4 g/mol.
3. Calculate the freezing temperature of an aqueous solution of ribose
(C
5
H
10
O
5
) with a mass fraction of 2%.
Answer
: –0.253
0
С.
4. Calculate the osmotic pressure at 310 K of the 20% aqueous solution
of glucose (ρ = 1.08 g/ml). What is this solution in comparison with blood:
isotonic, hypertonic or hypotonic? (π
osm
of blood 740–780 kPa)?
Answer
:
3091.3 kPa, hypertonic.
5. A solution obtained by dissolving 10.11 g of potassium nitrate in distilled
water weighing 246 g boils at 100.40 °C. Calculate the isotonic coefficient of
potassium nitrate in this solution.
Answer
: 1,9.
6. Prove that 0.9% NaCl solution (ρ = 1.005 g/ml) is isotonic to blood.
7. The solution contains 6.33 g of the hematin in 100 ml. The osmotic
pressure of this solution is 243.4 kPa at 20 °C. Determine the molar mass of
hematin.
Answer
: 633.2 g/mol.
Laboratory work:
Determination of the molecular weight of non-electrolyte
(urea).
Calculate the molecular mass of the solute according to Raoul’s formula:
∆t
freezing
=
K
k
×b (X), where
b
(X) is the molality of solution.
Determination of the molecular weight by the cryometric method is reduced
to the determination of freezing point ∆t. Pour 1 ml of solution in the test tube