Chapter No 7
Solution and suspension
Prepared by SLPS experienced staff
1.
2.
Haq Nawaz (M.phil, MSc applied chemistry with distinction (UK)
Farkhanda (MSc Organic Chemistry)
Q. Write note on solution, solute and solvent.
Solution:
Definition: The homogeneous mixture of two or more substances
is called solution
Explanation: When a substance such as salt is dissolved in
water it forms homogeneous mixture called solution. There are no
visible boundaries between components of solution. The
components of solution can be separated by physical method
because solution is mixture not a compound. The main
components of solution are solute and solvent. The particles of
solute can pass through filter paper. The particles of solution will
not settle down at bottom of container if left for long time.
Example. Sugar solution, salt solution etc
Solute: The component of solution which is dissolved and
present in smaller quantity is called solute.
Example: In salt solution, the salt is solute because it is dissolved
in water and present in smaller quantity
Solvent: The component of solution which dissolves solute and
present in larger quantity is called solvent.
Example: In salt solution, the water is solvent because it dissolves
solute (salt) and present in larger quantity
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Q. Define binary solution and aqueous solution.
Binary solution: The solution which only contains two
components solute and solvent is called binary solution OR the
solution in which only one solute is dissolved in given solvent is
called binary solution
Example: sodium chloride solution is called binary solution
because only sodium chloride is dissolved in water.
Aqueous solution: When solute is dissolved in water is called
aqueous solution or The solution in which water is used as a
solvent is called aqueous solution.
Example: sodium chloride solution is called aqueous solution
because water is used as a solvent
Q. what is the difference between dilute and concentrated
solution?
Dilute solution: the solution which contains small amount of
solute is called dilute solution or solution in which small amount of
solute is dissolved in given amount of solvent is called dilute
solution
Concentrated solution: the solution which contains high amount
of solute is called concentrated solution OR solution in which high
amount of solute is dissolved in given amount of solvent is called
concentrated solution
Example: the solution of 5g NaCl in water is dilute as compared to
25 g NaCl in water.
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Q. What are saturated, unsaturated and supersaturated
solution?
Saturated Solution:
Definition: The solution in which more solute cannot be dissolved
at given temperature is called saturated solution.
Explanation: When solute is being added to a solvent at
particular temperature the time will come when solvent cannot
dissolve anymore solute. If more solute is added after that it will
remain undissolved and settle down at the bottom. Such solution
which cannot dissolve anymore solute is called saturated solution
Unsaturated Solution:
Definition: The solution in which more solute can be dissolved at
given temperature is called unsaturated solution.
Explanation: An unsaturated solution is a solution which has
less amount of solute than it is required to saturate it a particular
temperature. If more solute is added it will dissolve in solution. For
example if we dissolve small amount of sugar in water then
solution will call unsaturated solution because it has a capacity to
dissolve more sugar.
Supersaturated solution: The solution which contains more
amount of solute than required for its saturation at given
temperature is called supersaturated solution. Or the solution
which is more concentrated than saturated solution is called
supersaturated solution.
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Explanation: When saturate solution is heated, it dissolves more
solute. After dissolving more solute on heating, when temperature
is reduced to room temperature then such solution is more
concentrated than a saturated solution and called supersaturated
solution.
Q. How can be distinguished between saturated, unsaturated
and supersaturated solution?
Ans: The three solutions can be easily distinguished by throwing
crystals of solute to each three forms of solution.
a. If the crystal dissolves the solution is unsaturated
b. if it remains unchanged or undissolved it is saturated
c. if some of the dissolved solute crystallized then it is
supersaturated.
Q. What are the types of solution of the basis of physical states
Ans
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Q. Do you know that metals can also form solution? If yes give
examples
Ans. Yes metals can also form solution called alloy. for examples
brass (homogeneous mixture of coppe and zinc), Amalgam and
Bronze (mixture of copper an tin) etc
Standard Solution: the solution of known concentration is called
standard solution.
Q. what is meant by strength or concentration of solution?
Concentration of solution: The amount of solute dissolved in a
given amount of solvent or solution is called concentration of
solution.
Mathematically
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Concentration of solution =
OR
Concentration of solution =
Both parts of the ratio can be taken in different measuring units
such as mass, volume, or moles. Therefore concentration of
solution can be expressed in several ways
Q. what are the different units of concentration of solution?
Ans: There are many ways to express concentration of solutions
but the two important methods are given below
1.Percentage composition: The number of parts of solute
present in 100 parts of solution is called percentage composition.
The percentage composition of solution can be expresses in the
following ways
a. Weight-weight percentage (w/w). When both solute and
solvent are taken on the basis of weight is called weight to weight
percentage
Example: 5%w/w solution means that 5 gram solute is dissolved
in 95 gram solvent to make 100 gram solution
b. Weight- Volume percentage (w/v%). When solute is taken on
the basis of weight and solvent on the basis of volume is called
weight to volume percentage (w/v%)
Example: 5%w/v solution means that 5 grams of solute are
dissolved in solvent to make 100 ml solution
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c. Volume-weight percentage (v/w%). When solute is taken on
the basis of volume and solvent on the basis of weight is called
volume-weight percentage (v/w%)
Example: 5%v/w solution means that 5 ml of solute is dissolved in
solvent to make 100 gram of solution
d. volume-volume percentage (v/v%). When both solute and
solvent are taken on the basis of volume is called volume-volume
percentage (v/v%)
Example: 5%v/v solution means that 5 ml of solute is dissolved in
95ml solvent to make 100 ml of solution
2. Molarity: The number of moles of solute present in 1litre (1dm3)
solution is called molarity OR the number of moles of solute
dissolve in one litre solution is called molarity.
Mathematically:
Molarity =
But
Mole =
So Molarity =
ℎ
ℎ
ℎ
ℎ
Example: 5.85 gram of NaCl is dissolved in water to make
500cm3 solution. Determine the molarity of the solution.
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Ans.
Given weight of NaCl = 5.85 gram
Molecular weight of NaCl = 23 + 35.5 = 58.5
Mole of NaCl =
ℎ
Volume of solution in dm3 =
Molarity =
ℎ
500
1000
=
5.85
58.5
= 0.1mole
= 0.5 dm3
= 0.1/0.5 = 0.2 M
Q. What is solubility? Explain different factors affecting
solubility?
Solubility: The number of grams of the solute necessary to
saturate 100gm of the solvent at particular temperature is called
solubility.
OR
The maximum amount of solute in grams required to saturate 100
grams of solvent at given temperature is called solubility.
Factors affecting solubility
The following three factors affecting solubility of a substance
(1) Temperature
(2) Nature of solute or solvent
(3) Pressure
1. Effect of temperature
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Generally in many cases solubility increases with the increase
in temperature and decreases with the decrease in temperature
but it is not necessary in all cases. However we must follow two
behaviors:
a. In endothermic process solubility increases with the increase
in temperature and vice versa.
For example: solubility of potassium nitrate increases with the
increase in temperature because absorbs heat on dissolution
b. In exothermic process solubility decreases with the increase
in temperature.
For example: solubility of calcium oxide decreases with the
increase in temperature because release heat on dissolution.
Gases are more soluble in cold solvent than in hot solvent.
2. EFFECT OF PRESSURE
The solubility of solids and liquids are not affected by pressure
because solids and liquids are incompressible. The effect of
pressure is observed only in the case of gases.
The solubility of gases in liquid is directly proportional to pressure
above the liquid i.e the solubility of gases increase with increase
in pressure
For example carbon dioxide is filled in cold drink bottles (such
as coca cola, Pepsi 7up etc.)under high pressure because to
increase solubility of carbon dioxide in cold drinks.
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3. Nature of solute and solvent
Solubility of a solute in a solvent purely depends on the nature
of both solute and solvent.
Polar solutes are dissolved in polar solvent and non polar solute
in non polar solvents. A polar solute has low solubility or
insoluble in a non-polar solvent.
For example. NaCl is soluble in water but not in benzene or
kerosene oil.
Similarly nature of solutes also affects solubility in same solvent.
For example, sodium chloride has more solubility than sugar in
water.
Q. Explain solute solvent interaction. How it effect solubility?
Solute-solvent interaction: the forces of interaction between
solute and solvent particles which help solute to dissolve in
solvent are called solute solvent interaction. In other words “like
dissolves like”. If the forces of solute and solvent interaction are
similar the solute will be soluble in solvent. For example, non
polar solutes are soluble in non polar solvent and polar solutes
are soluble in polar solvents. If interaction forces are dissimilar the
solute will be insoluble in solvent. For example polar solute is
insoluble in non polar solvent.
Solute is soluble in solvent when Solute-solvent interaction
greater than solvent-solvent interaction and solute-solute
interaction.
Q. Why polar solutes dissolve in polar solvent and non polar
in non polar solvent
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Ans. The force of attraction between polar solute and polar
solvent is very strong which overcome on solute- solute
interaction so polar solutes are soluble in polar solvent. Similarly
the force of attraction between non polar solute and non polar
solvent is very strong which overcome on solute- solute
interaction so non polar solutes are soluble in non polar solvent.
In contrast the interaction forces are very weak between polar
solute and non polar solvent or vice versa so polar solutes
insoluble in non polar solvent and non polar insoluble in polar
solvent.
Q. What is solution formation or dissolution? Explain
solution formation by hydration and hydrogen bonding or
why water is universal solvent?
Solution formation or dissolution: the process in which solute
is dissolved in solvent is called solution formation
Water has the property that it can dissolve most of solutes ( both
ionic and polar) so called universal solvent. Water dissolves
majority of compounds due to the following characteristics.
a. Solution formation by hydration: The surrounding of water
molecules around positive and negative ions when ionic
compounds are dissolved in water is called hydration.
Example: Water is polar compound having positive and negative
poles. When ionic compound such as sodium chloride is
dissolved in water, it breaks crystal lattice of sodium chloride into
positive sodium ions and negative chlorine ion. These ions are
surrounded by water molecules in such way that negative pole of
water directed towards positive sodium ion and positive pole
toward negative chlorine ion which is called hydration.
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Hydration of sodium chloride
b. Solution formation by hydrogen bonding: water dissolves
some compounds by forming hydrogen bonds with them. For
example ethyl alcohol and sugar are dissolved in water due
to formation of hydrogen bonding between water molecules
and solutes.
Q. 11 write note on suspension and colloids.
Ans: Suspension: A heterogeneous mixture of two or more
substances having none uniform composition throughout and
contains insoluble particles in solvent is called suspension. Its
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composition is not uniform throughout and solute particles can be
seen with naked eye. The particles cannot pass through filter
paper. The particles of suspension settle down at bottom if left for
long time.
For examples, 1) mixture of chalk
2) mud in water
Colloids or colloidal solution: The solution in which the solute
particles are bigger in size than the solute particles of a solution
but smaller than the solute particles of suspension is called colloid
or colloidal solution.
The particles are not so big that can be seen with naked eyes but
can be seen with powerful microscope. The particles can be
passed from filter paper but not from animal membrane. The
particles do not settle down at the bottom.
For examples, 1) mixture of starch in water
2) milk
Colligative properties: those properties which depend upon the
number of particles but not on nature of particles are called
colligative properties
For example, increase in boiling point and decrease in freezing
point of solution
Hydrated ions: The ions which are completely surrounded by
water molecules are called hydrated ions and process is called
hydration
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Solvated ion: The ions which are completely surrounded by
solvent molecules are called solvated ions and process is called
salvation.
Exercise
Q1 choose the correct answer
i)c ii)c iii)c iv)b v)b vi)b vii) a viii)b ix)b x)d
Q. 4 see question on page 103
Ans
Given data: Given mass of NaOH = 100 g
Molecular mass (FM) of NaOH = 23 + 16 +1 = 40
Volume of solution: 1dm3
Required data: Molarity of NaOH = ?
Solution:
Molarity =
ℎ
ℎ
Q.5 see question on page 103
=
100
40 1
3
= 2.5M
Ans
Given data: Given mass of Na2CO3 = 0.530g
Molecular mass (FM) of Na2CO3 = (2x23) + 12 +(3x16) = 106
Volume of solution = 250 cm3 = 250/1000=0.25dm3
Required data: Molarity of Na2CO3 = ?
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Solution:
Molarity =
ℎ
ℎ
=
0.53
106 0.25
3
= 0.02M
Q. see question on page 103
Ans
Given data: Given mass of NaOH 5% = 5 g
Molecular mass (FM) of NaOH = 23 + 16 +1 = 40
Volume of solution = 100cm3 = 100/1000= 0.1 dm3
Required data: Molarity of NaOH = ?
Solution:
Molarity =
i)
ℎ
ℎ
=
5
40 0.1
3
= 1.25M
Hydration is always called solvation but salvation is
not always called hydration.
Reason: Solvation is the process in which solute particles are
surrounded by solvent molecules but when water is used as a
solvent then it is also called hydration. As every solvent is not
water therefore hydration is always called 15alvation but
15alvation is not always called hydration.
ii)
Dissolution of NaCl in water is physical change not a
chemical change.
Reason: Dissolution of NaCl in water is physical change not a
chemical change because
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



iii)
both substances retain their original properties
No bond formation or breaking take place
No new compound is formed
Both components can be separated by physical method
(evaporation and condensation)
Sugar dissolves less readily in water as compared to
NaCl
Reason: Solubility of substances depends upon solute-solvent
interaction. Sugar dissolves less readily in water as compared
to NaCl because solute solvent interaction of sugar is weaker
than NaCl solute solvent interaction. Additionally hydration
takes place when sodium chloride is dissolved in water but
hydrogen bonding tale place when sugar is dissolved in water
where hydration completely separates positive negative ions.
iv)
Acetone is used to remove the nailpolish instead of
washing with water
Reason: Acetone is used to remove the nailpolish instead of
washing with water because “like dissolves like”. Nail polish is
non polar so must be dissolved in acetone which is also non
polar. Water is polar so cannot be used to remove nailpolish
which is non polar.
v)
The vapour pressure of ether is greater than the
vapour pressure of water
Reason: The vapour pressure of ether is greater than water
because the intermolecular forces of ether are weaker than
water and vapour pressure inversely proportional to
intermolecular forces. Stronger the intermolecular forces lower
will be vapour pressure.
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