6 / 58
4
There is an inverse relationship between the masses of solutions and the
mass fractions of the dissolved substances:
You can calculate the mass of a 20% solutionby this formula, and then
calculate the volume of this solution by the formula:
The mass and volume of the solvent (H
2
O) is determined as follows:
m
(H
2
O) = 200 –
m
(20% solution). Since ρ (H
2
O) = 1 g/ml,
m
(H
2
O) =
V
(H
2
O).
Using a graduated cylinder, measure the calculated volumes of 20% NaCl
solution and water, pour into a flask and mix. Check the density of your solu-
tion with a hydrometer. The resulting solution pour into the cylinder and lower
the hydrometer there, write down the density of the prepared solution by the
hydrometer. Using the density table of sodium chloride solutions, calculate the
concentration of the prepared solution and compare it with the concentration,
that given by the teacher. Make a conclusion about the correct preparation of
sodium chloride solution.
LESSON 2.
ACID-BASIC TITRATION:
ALKALIMETRY AND ACIDIMETRY
Required base level.
Percentage concentration; molarity; normality. Neutralization reactions.
Strong and weak acids and bases, degree of dissociation.
Questions for the preparation for the lesson.
1. Molarity, titer, normality, law of equivalents.
2. pH of the solution, the equation for calculating the pHvalue.
3. Titration, neutralization method: the essence of the method, titrants,
burette.
4. Methods of performing the analysis. Measuring utensils.
5. Indicators, used in the neutralization method. Selection an indicator to
determine the equivalence point.
sol
m V
ρ
=
1
2
2
1
m
m
=
ω
ω