Types of Solution
There are different types of solutions based on their distinct properties. They are
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Aqueous Solutions
Non aqueous Solutions
Concentrated Solutions
Dilute Solutions
Saturated Solutions
Unsaturated Solutions
Supersaturated solutions
Solid solutions
Gaseous solutions
1. Non - Aqueous Solutions
It is a solution where the solvent is something other than water. For example, iodine in alcohol,
acetone in benzene are example of non-aqueous solution.
2. Concentrated Solutions and Dilute Solutions
Between two solutions, the solute quantity may be different. The solution that has more
proportion of solute is said to be concentrated. If the proportion of solute is less, the solution is a
dilute solution. The concentration of a solution is expressed as the amount of solute present in a
given amount (mass or volume) of the solution; or the amount of solute dissolved in a given
mass or volume of a solvent. It is expressed as a percentage of these quantities.
3. Supersaturated solutions
The solubility of the salt will increase with increase in temperature. Hence we can add more
solute to the saturated solution at an elevated temperature (nearly at its boiling point). A solution
where the solute cannot be added further even at elevated temperature is called a super saturated
solution. It is highly unstable and the solute will crystallize when the temperature is reduced.
4. Gaseous solution
Gases diffuse uniformly to form a homogeneous mixture. Air is such a homogeneous mixture of
many gases like nitrogen, oxygen, carbon dioxide etc. A gaseous solution is a uniform solution
of two or more non reactive gases.
Concentration of Solutions
The concentration of solution is expressed in different terms.
1. Volume/volume percent: It is the volume of solute present in 100ml of solution. It is the
most common method used when both solute and solvent are liquids. It is denoted by v/v.
For example, if it is shown that the concentration of ethanol is 15% v/v, it means that
15ml of ethanol is present in 100ml of solution.
2. Mass/mass percent: It is the mass of solute present in 100g of solution. It is denoted as
w/w. It is commonly used when the solute is in solid state. For example, if it is shown
that the concentration of glucose solution in a bottle as 10% w/w. It means that 10g of
glucose is present in 100g solution.
3. Moles per liter/Molarity: It is the number of moles of solute present in 1 liter of
solution. It is expressed in moles/liter.
4. Moles per kg of solvent/molality: It is the number of moles of solute present in 1kg of
solvent. It is expressed in moles/kg.
5. Mole fraction: It is the ratio of the number of moles of one component to the total
number of moles in the system. Generally the sum of the mole fractions of all
components is equal to 1.
Solubility
Solubility is a measure that denotes the maximum amount of substance that can be dissolved in a
solvent in a saturated solution. It is the amount of solute present in 100ml of a saturated solution
at a particular temperature. It depends on temperature, nature of substance, pressure.
1. Temperature: Temperature is directly related with solubility. When we increase the
temperature, more energy is given to break the molecules. Hence the solubility increases
on increasing the temperature.
2. Nature of substance: In solubility 'like dissolves like', which means that non polar
substances can dissolve well in non polar solvents like benzene etc. Similarly polar
substances like sodium chloride will dissolve in polar solvents like water.
3. Pressure: Pressure will affect the solubility of a gas in a liquid. Hence the solubility of
gas is directly related to the pressure of the gas over the liquid. It is well known as
Henry's law.
The other term closely related with solubility of the substance is 'solubility product'. It is the
product of the concentration of ions produced in a solution at a particular concentration.
Properties of Solution
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The solution is homogeneous, which means that both solute and solvent are in the same
state which cannot be differentiated easily.
The solution is stable, which means that the solute particles will not settle down in time.
The properties of a solution are different from the solute and solvent. In the case of solid
solutions like alloys, the properties like melting point, refractive index are entirely
different from the parent metals. Similarly for liquid solutions, the melting point and
boiling point are different from a pure solvent.
Aqueous Solution
In the solution if the solvent is water it is called an aqueous solution. For example sodium
chloride in water and copper sulphate in water are some examples for aqueous solution. Water is
a universal solvent.
Due to the high dielectric constant and high intermolecular space, the solutes can undergo either
dissociative dissolving or undissociative dissolving. For example sodium chloride breaks up as
sodium and chloride ions in water but sugar molecules retain their identify in solution level also.
Saturated Solution
Saturated solution is a solution to which no more solute can be added at a particular temperature.
As temperature affects the solubility of a substance, a saturated solution at lower temperature
may become a dilute solution at higher temperature.
Unsaturated Solution
It is a solution to which more solute can be added to dissolve. They are also otherwise called
dilute solutions. The concentration of a solution is very low in an unsaturated solution.
Solid Solutions
It is the type of solution in which both solute and solvent are solids. For example metal alloys are
a homogeneous mixture of two or more metals and their properties are entirely different from the
parent metals.
Liquid Solutions
In a solution if both the solute and solvent are liquid they are called as liquid solutions. Ethanol
in water, Benzene in carbon tetra chloride are example for liquid solutions.
Types of solutions
All the three states of matter (gas, liquid or solid) may behave either as solvent or solute. Depending on the state of
solute or solvent, mainly there may be following nine types of binary solutions.
Solvent
Solute
Example
Gas
Gas
Mixture of gases, air.
Gas
Liquid
Water vapors in air, mist.
Gas
Solid
Sublimation of a solid into a gas, smoke.
Liquid
Gas
CO2 gas dissolved in water (aerated drinks).
Liquid
Liquid
Mixture of miscible liquids, e.g., alcohol in water.
Liquid
Solid
Salt in water, sugar in water.
Solid
Gas
Adsorption of gases over metals; hydrogen over palladium.
Solid
Liquid
Mercury in zinc, mercury in gold,CuSO4.5H2O.
Solid
Solid
Homogeneous mixture of two or more metals (alloys), e.g., copper in gold,
zinc in copper.
Among these solutions the most significant type of solutions are those which are in liquid phase and may be
categorized as, (1) Solid in liquid solutions, (2) Liquid in liquid solutions and (3) Gas in liquid solutions.
Properties of Water
A. Cohesive behavior
1.Explanation: Water molecules form hydrogen bonds with one another causing
high surface tension.
2. Eg. a water strider walks on the surface of a pond. Lab- Pepper floats on
surface of water until soap is added. Water droplets form bubble on the top of a
penny.
B. Adhesive behavior
1.Explanation: Water Molecules form hydrogen bonds with other polar molecules
causing capillary action.
2.Eg. Water crawls up a narrow glass tube and paper.
Lab- water advances up paper down when tip is dipped in.
C. High heat capacity
1.Explanation: Hydrogen bonding causes H2O to absorb a large amount of heat
before its temperature increases appreciably and also causes it to lose large
amounts of heat before its temperature decreases significantly causing
temperature moderation.
2.Eg. HIgh heat capacity helps organisms maintain a constant body temperature.
D. High specific heat of vaporization
1.Explanation: Hydrogen bonding causes liquid H2O to absorb a large amount of
heat to become a vapour(gas) and causes evaporative cooling.
2.Eg. May organisms including humans dissipate body heat by evaporation of
H2O from surfaces, such as skin(by sweating) and tongue(by panting)
E. Expansion of water upon freezing
1.Highest density of water at 4 degrees Celsius
Explanation: AS H2O molecules cool below 0 degrees C, they form a crystalline
lattice (freezing). The hydrogen bonds between the V-shaped molecules spread
the molecules apart, reducing the density below that of liquid water causing ice to
float on water.
2.The expansion upon freezing comes from the fact that water crystallizes into an open
hexagonal form. This hexagonal lattice contains more space than the liquid state.
F. Versatility as a solvent
1.it is able to dissolve many substances due to its polarity