These are homogeneous (homogeneous) systems consisting of two or more components and products of their interaction.
Precise determination of the solution (1887 D.I. Mendeleev)
Solution is a homogeneous (homogeneous) system consisting of
dissolved particles
substance, solvent
and products
their interactions.
Solutions are divided into:
- Molecular - aqueous solutions of non-electrolytes
(alcoholic solution of iodine, glucose solution).
- Molecular-ionic - solutions of weak electrolytes
(nitrogen and carbonic acid, ammonia water).
3. Ionic solutions - solutions of electrolytes.
1g Practically Insoluble S" width="640" Solubility -
the property of a substance to dissolve in water or another solution.
Solubility factor(S) is the maximum number of grams of a substance that can be dissolved in 100 grams of solvent at a given temperature.
Substances.
Slightly soluble
S \u003d 0.01 - 1 g
Highly soluble
Practically Insoluble
S 
Influence of various factors on solubility.
Temperature
Pressure
Solubility
The nature of the solutes
The nature of the solvent
Solubility of liquids in liquids in a very complex way depends on their nature.
Three types of liquids can be distinguished, differing in their ability to mutually dissolve.
- Practically immiscible liquids, i.e. incapable of forming mutual solutions(for example, H 2 0 and Hg, H 2 0 and C 6 H 6).
2) Liquids mixed in any ratio, i.e. with unlimited mutual solubility(for example, H 2 0 and C 2 H 5 OH, H 2 0 and CH 3 COOH).
3) Liquids with limited mutual solubility(H 2 0 and C 2 H 5 OS 2 H 5, H 2 0 and C 6 H 5 NH 2).
Significant impact pressure affects only the solubility of gases.
Moreover, if there is no chemical interaction between the gas and the solvent, then according to
Henry's law the solubility of a gas at constant temperature is directly proportional to its pressure over the solution
Methods for expressing the composition of solutions 1. share 2. Concentrations
Mass fraction of a solute in a solution is the ratio of the mass of the solute to the mass of the solution. (fractions of unit/percentage)
Solution concentration –
Molarity- the number of moles of a solute in 1 liter of solution.
ʋ - amount of substance (mol);
V is the volume of the solution (l);
Equivalent concentration (normality) - the number of equivalents of a solute in 1 liter of solution.
ʋ equiv. - number of equivalents;
V is the volume of the solution, l.
Expression of concentrations of solutions.
Molar concentration (molality) is the number of moles of solute per 1000 g of solvent.
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Slides captions:
Topic: WATER is a solvent. Soluble and insoluble substances in water. . Knowledge of the world
Tasks: 1. improve knowledge about water, about its significance; 2. show in experiments which substances dissolve and do not dissolve; 3. draw a conclusion about the importance of water for wildlife; 4. improve the skills of analysis and generalization by students of the knowledge gained; 5. education of careful attitude to water. 6. Ability to work in cooperation; Purpose: To introduce the property of water - solubility;
Guess the riddle WATER I am a cloud, and a fog, And a stream, and an ocean, And I fly, and I run, And I can be glass! WATER
Water properties 1. Transparent 2. Colorless 3. Odorless 4. Water flows. (property - fluidity) 5 . no form
Water in nature can be in three states Liquid Solid Gaseous water of rivers, oceans, seas rain dew hail ice snow frost steam
Sand Sugar Clay Salt
We are used to the fact that water is always our companion. Without it, we can't wash, Don't eat, don't get drunk. I dare to report to you, We cannot live without it. The role of water in nature
People, save water!
On the topic: methodological developments, presentations and notes
Water. methods for determining the composition of water. Water in nature, methods for its purification.
Development of a chemistry lesson in the 8th grade for students enrolled in the program of Rudzitis G.E., Feldman F.G. lesson material includes elements research activities students. to the lesson developed ...
The presentation made an introduction to the topic of the lesson, collected interesting additional material on the topic, a test on the studied material....
Extracurricular event "Water. Water. Water all around ..."
The purpose of the event: to raise the level of awareness of 8th grade students on the issue of water protection as the most important natural source of human life support. Information about the value of water, the content of e...
What then is a solution?
Solution (true solution) - a homogeneous system in which the particle size of the substance is less than 1 nm, there is no interface between the particles and the medium.
Any solution consists of:
- Solute
- Solvent
From two or more components of the solution solvent is the one taken in more quantity and has the same state of aggregation as the solution as a whole.
Types of aqueous solutions
Water + Solid
(CaCl 2 in H 2 O)
Water + Liquid
(H 2 SO 4 to H 2 O)
Water + Solid
How does dissolution occur?
Diffusion
The process of penetration of some molecules of a substance through others.
sugar molecules (white circles)
water molecules (dark circles)
Thermal phenomena during the dissolution of substances
Destruction of chemical and intermolecular bonds between ions, atoms or molecules of the dissolved substance and uniform distribution (diffusion) of the formed particles between water molecules.
energy consumption
Endothermic process
Interaction of particles of a dissolved substance with a solvent.
release of energy
exothermic process
Dissolution - This is a physico-chemical process in which, along with the formation of a conventional mechanical mixture of substances, there is a process of interaction of particles of a solute with a solvent.
Solubility
Solubility The ability of a substance to dissolve in water or another solvent.
Substances
Highly soluble
Slightly soluble
Insoluble
Solubility factor (S) is the maximum number of grams of a substance that can be dissolved in 100 grams of solvent at a given temperature.
saturated solution is a solution that is in dynamic equilibrium with the solute.
a solution in which a given substance no longer dissolves at a given temperature
Factors affecting solubility
- The nature of the solvent
- The nature of the solute
- Pressure
- Temperature
Solution concentration
Solution concentration - This is the content of a substance in a certain mass or volume of a solution.
Mass fraction of a solute in a solution is the ratio of the mass of the solute to the mass of the solution.
Solution concentration expression
Molarity - the number of moles of a solute in 1 liter of a solution
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Solutions The solution is a homogeneous, multicomponentvariable composition system containing
products of interaction of components -
solvates (for aqueous solutions - hydrates).
Homogeneous means homogeneous, single-phase.
A visual sign of liquid homogeneity
solutions is their transparency. Solutions consist of at least two
components: solvent and soluble
substances.
The solvent is the component
the amount of which in solution is usually
dominates, or that component, aggregate
whose state does not change
solution formation.
Water
Liquid The solute is
missing component, or
component whose state of aggregation
changes during the formation of a solution.
Solid salts
Liquid The components of solutions retain their
unique properties and do not enter into
chemical reactions with each other
the formation of new compounds
.
BUT
solvent and solute, forming
solutions interact. Process
interactions between solvent and solute
substances is called solvation (if
the solvent is water - hydration).
As a result of chemical interaction
solute with solvent
more or less stable
complexes characteristic only for solutions,
which are called solvates (or hydrates). The core of a solvate is formed by a molecule, atom, or
an ion of a solute, a shell -
solvent molecules. Several solutions of the same substance will
contain solvates with a variable number of molecules
shell solvent. It depends on the quantity
solute and solvent: if solute
there is little substance, and there is a lot of solvent, then the solvate has
saturated solvation shell; if dissolved
a lot of substance - a rarefied shell.
The variability of the composition of solutions of the same
substances are usually shown by differences in their concentration
non-concentrated
solution
Concentrated
solution Solvates (hydrates) are formed by
donor-acceptor, ion-dipole
interactions or due to hydrogen
connections.
Ions are especially prone to hydration (as
charged particles).
Many of the solvates (hydrates) are
fragile and easily decomposed. However, in
in some cases strong
compounds that can be isolated from
solution only in the form of crystals,
containing water molecules, i.e. as
crystalline hydrates.
Dissolution as a physical and chemical process
The process of dissolution (essentially a physical processcrushing of a substance) due to the formation of solvates
(hydrates) may be accompanied by the following phenomena
(characteristic of chemical processes):
takeover
change
or release of heat
volume (as a result of the formation
hydrogen bonds); highlighting
gas or precipitation (due to
ongoing hydrolysis);
change in the color of the solution relative to the color
solute (as a result of the formation
aquacomplexes), etc.
freshly prepared solution
(emerald color)
solution after some time.
(gray-blue-green)
These phenomena make it possible to attribute the dissolution process to
complex, physico-chemical process.
Solution classifications
1. According to the state of aggregation:- liquid;
- hard (many metal alloys,
glass). 2. By the amount of dissolved substance:
- unsaturated solutions: in them dissolved
less substance than it can dissolve
this solvent at normal
conditions (25◦С); these include the majority
medical and household solutions. . Saturated solutions are solutions in which
of which there is so much solute,
how much can this dissolve
solvent under normal conditions.
A sign of saturation of solutions
is their inability to dissolve
the amount added to them
solute.
These solutions include:
waters of the seas and oceans,
liquid human
organism. supersaturated solutions are solutions in which
of which there is more solute than
can dissolve the solvent
normal conditions. Examples:
carbonated drinks, sugar syrup. Supersaturated solutions are formed
only in extreme conditions: at
high temperature (sugar syrup) or
high pressure (carbonated drinks). Supersaturated solutions are unstable and
when returning to normal conditions
"grow old", i.e. delaminate. Excess
solute crystallizes or
released in the form of gas bubbles
(returns to the original aggregate
condition). 3. According to the type of solvates formed:
-ionic solutions - solute
dissolves into ions.
-Such solutions are formed under the condition
the polarity of the solute and
solvent and redundancy of the latter. Ionic solutions are quite resistant to
stratification, and are also capable of conducting
electric current (they are conductors
electric current of the II kind) - molecular solutions - soluble
matter breaks down into molecules.
Such solutions are formed under the condition:
- polarity mismatch
solute and solvent
or
- the polarity of the solute and
solvent, but insufficiency
the last one.
Molecular solutions are less stable
and are unable to conduct electricity. Scheme of the structure of the molecular solvate on
soluble protein example:
Factors affecting the dissolution process
1. The chemical nature of the substance.Direct impact on the process
dissolution of substances renders their polarity
molecules, which is described by the similarity rule:
like dissolves into like.
Therefore, substances with polar molecules
readily soluble in polar
solvents and bad in non-polar and
vice versa. 2. Temperature.
For most liquids and solids
characterized by an increase in solubility at
rise in temperature.
Solubility of gases in liquids with
decreases with increasing temperature, and
decrease - increases. 3. Pressure. With increasing pressure
solubility of gases in liquids
increases, and with a decrease
decreases.
On the solubility of liquid and solid
substances are not affected by pressure changes.
Methods for expressing the concentration of solutions
There are various waysexpressions for the composition of the solution. Most often
used such as mass fraction
solute, molar and
mass concentration.
Mass fraction of the dissolved substance
This is a dimensionless quantity equal to the ratiomass of solute to total mass
solution:
w%=
msubstances
m solution
100%
For example, a 3% alcohol solution of iodine
contains 3g of iodine in 100g of solution or 3g of iodine in 97g
alcohol.
Molar concentration
Shows how many moles of dissolvedsubstances contained in 1 liter of solution:
CM =
substances
VM
solution
=
msubstances
Substances ´
solution
Substances - the molar mass of the dissolved
substances (g/mol).
The unit of measure for this concentration
is mol/l (M).
For example, a 1M solution of H2SO4 is a solution
containing in 1 liter 1 mol (or 98g) sulfuric
Mass concentration
Indicates the mass of a substancein one liter of solution:
C=
substances
V solution
The unit of measurement is g/l.
This method is often used to evaluate the composition
natural and mineral waters. Theory
electrolytic
dissociation
ED is the process of electrolyte breakdown into ions
(charged particles) under the influence of polar
solvent (water) to form solutions,
capable of conducting electricity.
Electrolytes are substances that can
break down into ions.
Electrolytic dissociation
Electrolytic dissociation is causedinteraction of polar solvent molecules with
solute particles. it
interaction leads to polarization of bonds, in
resulting in the formation of ions due to
"weakening" and breaking bonds in molecules
solute. The transition of ions into solution
accompanied by their hydration:
Electrolytic dissociation
Quantitatively, ED is characterized by the degreedissociations (α); she expresses the attitude
dissociated molecules into ions to
the total number of molecules dissolved in the solution
(changes from 0 to 1.0 or from 0 to 100%):
n
a = ´100%
N
n are molecules dissociated into ions,
N- total number molecules dissolved in
solution.
Electrolytic dissociation
The nature of the ions formed during dissociationelectrolytes are different.
In salt molecules, during dissociation,
metal cations and acid residue anions:
Na2SO4 ↔ 2Na+ + SO42 Acids dissociate to form H+ ions:
HNO3 ↔ H+ + NO3 Bases dissociate to form OH- ions:
KOH ↔ K+ + OH-
Electrolytic dissociation
According to the degree of dissociation, all substances can bedivided into 4 groups:
1. Strong electrolytes (α>30%):
alkalis
(highly water-soluble bases
group IA metals - NaOH, KOH);
monobasic
acids and sulphuric acid(HCl, HBr, HI,
HNO3, HClO4, H2SO4 (diff.));
all
salts soluble in water.
Electrolytic dissociation
2. Medium electrolytes (3%<α≤30%):acids
– H3PO4, H2SO3, HNO2;
dibasic,
bases soluble in water
Mg(OH)2;
soluble
salts of transition metals in water,
entering the process of hydrolysis with a solvent -
CdCl2, Zn(NO3)2;
salt
organic acids - CH3COONa.
Electrolytic dissociation
3. Weak electrolytes (0.3%<α≤3%):lower
organic acids (CH3COOH,
C2H5COOH);
some
water soluble inorganic
acids (H2CO3, H2S, HCN, H3BO3);
nearly
all salts and bases that are sparingly soluble in water
(Ca3(PO4)2, Cu(OH)2, Al(OH)3);
hydroxide
water.
ammonium - NH4OH;
Electrolytic dissociation
4. Non-electrolytes (α≤0.3%):insoluble
majority
salts, acids and bases in water;
organic compounds (like
soluble and insoluble in water)
Electrolytic dissociation
The same substance can be both strong,and weak electrolyte.
For example, lithium chloride and sodium iodide, which have
ionic crystal lattice:
when dissolved in water behave like typical
strong electrolytes,
when dissolved in acetone or acetic acid
are weak electrolytes with a degree
dissociation is less than unity;
in a "dry" form they act as non-electrolytes.
Ionic product of water
Water, although it is a weak electrolyte, partially dissociates:H2O + H2O ↔ H3O+ + OH− (correct, scientific notation)
or
H2O ↔ H+ + OH− (abbreviated notation)
In perfectly pure water, the concentration of ions at n.o. always constant
and is equal to:
IP \u003d × \u003d 10-14 mol / l
Since in pure water = , then = = 10-7 mol/l
So, the ionic product of water (IP) is the product of concentrations
hydrogen ions H+ and hydroxyl ions OH− in water.
Ionic product of water
When dissolved in water, anysubstances equality of ion concentrations
= = 10-7 mol/l
may be violated.
Therefore, the ionic product of water
allows you to determine the concentration and
any solution (that is, determine
acidity or alkalinity).
Ionic product of water
For the convenience of presenting the resultsacidity/alkalinity environment enjoy
not absolute values of concentrations, but
their logarithms - hydrogen (pH) and
hydroxyl (pOH) indicators:
+
pH = -lg[H]
-
pOH=-lg
Ionic product of water
In a neutral medium = = 10-7 mol/l and:pH \u003d - lg (10-7) \u003d 7
When acid (H+ ions) is added to water,
the concentration of OH- ions will fall. Therefore, at
pH< lg(< 10-7) < 7
the environment will be acidic;
When alkali (OH– ions) is added to water, the concentration
will be more than 10−7 mol/l:
-7
pH > log(> 10) > 7
, and the environment will be alkaline.
Hydrogen index. Indicators
Acid-base pH is used to determine pH.indicators - substances that change color in
depending on the concentration of H + and OH- ions.
One of the best known indicators is
universal indicator, colored at
excess H + (i.e. in an acidic environment) in red, with
excess OH- (i.e. in an alkaline environment) - in blue and
having a yellow-green color in a neutral environment:
Salt hydrolysis
The word "hydrolysis" literally means "decompositionwater."
Hydrolysis is the process of interaction of ions
solute with water molecules
formation of weak electrolytes.
Since weak electrolytes are released as
gas, precipitate or exist in solution in
undissociated form, then hydrolysis can be
consider a chemical reaction of a solute
with water.
1. To facilitate writing hydrolysis equations
All substances are divided into 2 groups:
electrolytes (strong electrolytes);
non-electrolytes (medium and weak electrolytes and
non-electrolytes).
2. Acids and
bases, since the products of their hydrolysis are not
differ from the original composition of the solutions:
Na-OH + H-OH = Na-OH + H-OH
H-NO3 + H-OH = H-NO3 + H-OH
Salt hydrolysis. Writing rules
3. To determine the completeness of hydrolysis and pHsolution write 3 equations:
1) molecular - all substances are presented in
the form of molecules;
2) ionic - all substances capable of dissociation
are written in ionic form; in the same equation
free identical ions are usually excluded from
left and right parts of the equation;
3) final (or resulting) - contains
the result of the "reductions" of the previous equation.
Salt hydrolysis
1. Hydrolysis of a salt formed by a strongbase and strong acid:
Na+Cl- + H+OH- ↔ Na+OH- + H+ClNa+ + Cl- + H+OH- ↔ Na+ + OH- + H+ + ClH+OH- ↔ OH- + H+
Hydrolysis does not occur, the solution medium is neutral (because
the concentration of OH- and H+ ions is the same).
Salt hydrolysis
2. Hydrolysis of a salt formed by a strong base andweak acid:
C17H35COO-Na+ + H+OH- ↔ Na+OH- + C17H35COO-H+
C17H35COO- + Na+ + H+OH- ↔ Na+ + OH- + C17H35COO-H+
C17H35COO- + H+OH- ↔ OH- + C17H35COO-H+
Hydrolysis partial, by anion, solution medium alkaline
OH-).
Salt hydrolysis
3. Hydrolysis of a salt formed by a weak base andstrong acid:
Sn+2Cl2- + 2H+OH- ↔ Sn+2(OH-)2 ↓+ 2H+ClSn+2 + 2Cl- + 2H+OH- ↔ Sn+2(OH-)2 + 2H+ + 2ClSn+2 + 2H +OH- ↔ Sn+2(OH-)2 + 2H+
Hydrolysis partial, by cation, solution medium acidic
(because an excess of ions remains in the solution in a free form
H+).
Salt hydrolysis
4. Hydrolysis of a salt formed by a weak base and a weakacid:
Let's try to get an aluminum acetate salt in the exchange reaction:
3CH3COOH + AlCl3 = (CH3COO)3Al + 3HCl
However, in the table of solubility of substances in water of such
there is no substance. Why? Because it comes into play
hydrolysis with water contained in the initial solutions
CH3COOH and AlCl3.
(CH3COO)-3Al+3+ 3H+OH- = Al+3(OH-)3 ↓+ 3CH3COO-H+
3CH3COO-+ Al+3 + 3H+OH- = Al+3(OH-)3 ↓+ 3CH3COO-H+
Hydrolysis is complete, irreversible, the medium of the solution is determined
electrolytic power of hydrolysis products.