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LESSON 1.
WAYSOF EXPRESSION
OF CONCENTRATION OF SOLUTIONS
Required base level.
Percent Concentration; molarity. Methods of preparing solutions.
Questions for the preparation for the lesson.
1. Solutions. Density of solutions. The role of solutions in the vital functions
of the human body.
2. Ways of expressing the concentration of solutions: the mass fraction of
the dissolved substance, the molarity, the normality, the mole fraction, molality,
the titer of the solution.
3. Chemical equivalent. Equivalents of salts, acids, bases;
4. Ways of converting one concentration into another.
Homework exercises.
1. To 250 g of a 10% solution were added 150 g of water. Calculate the
percentage concentration of solute in the new solution?
Answer
: 6.25%.
2. What mass of iodine is needed to prepare 200 g of 5% iodine tincture?
What volume of alcohol (ρ = 0.8 g/ml) is required for this?
Answer
: 10 g
of iodine and 237.5 ml of alcohol.
3. A 10% solution of CaCl
2
(ρ = 1.04 g/ml) in ampoules is used to prepare
0.025M CaCl
2
solution. What volume of this solution is needed to prepare 1 liter
of a 0.025M solution?
Answer
: 26.7 ml.
4. Physiological saline is 0.9% NaCl solution (ρ = 1.005 g/ml). Calculate the
molarity, the normality, the molality of sodium chloride in saline.
Answer
:
b
=
0.154 mol0/kg;
C
=
C
eq
= 0.1546 mol/l.
5. What volume of 30% hydrochloric acid (ρ = 1.15 g/ml) and water will be
needed to prepare 450 g of a 2% solution?
Answer
: 26.09 and 420 ml.
Questions for self-study.
1. Properties ofwater.Auto-protolysis ofwater, the constant of autoprotolysis.
2. Solubility of substances, factors affecting solubility.
Laboratory work:
Preparation of sodium chloride solution by dilution.
Each studentreceives an individual assignment from the teacher. Example
task: to prepare 200 g of 8% solution of sodium chloride (NaCl) from a 20%
solution of this salt (ρ = 1.145 g/ml). Calculate the molarity, the normality, the
molality and the titer of the prepared solution.