Types of Solutions - Different Types, Heterogeneous, Examples, FAQs

As we understand it in chemistry, the concept of solutions involves a homogeneous mixture of two or more substances. The study and use of solutions date back to ancient times, but the formal introduction and systematic study of solutions can be attributed to the development of modern chemistry. Ancient civilizations understood the concept of solutions in a rudimentary form. For instance, early chemists and alchemists in ancient Egypt, China, and India used solutions in their practices, such as dissolving metals in acids.

This Story also Contains

1. Solutions
2. Concentration Of Solution
3. Some Solved Examples
4. Example.1
5. Summary

Solutions are important in various practical applications and lots of scientific studies in such a way that Solutions are crucial in multiple fields such as medicine (e.g., intravenous fluids), chemistry (e.g., reaction media), and industry (e.g., metal plating). Understanding solutions is fundamental to chemistry and physics as it affects how substances interact and react, influencing everything from biological processes to industrial operations.

Solutions

The solution is a homogeneous mixture of two or more chemically non-reacting substances whose composition can be varied within certain limits. A solution that contains only two components is called a binary solution. The component which has the same physical state as the solution is the solvent. If both the components have the same physical state, then the component present in a larger amount is called the solvent and the other present in a smaller amount is called the solute.

The solutions may be gaseous, liquids, and solids. The most common type of solution is the liquid solution (gas in liquid, liquid in liquid, solid in liquid). In all, we can divide solutions into nine different classes as follows:

Concentration Of Solution

The concentration of a solution gives us an idea about the relative amount of solute and solvent present in the solution. The concentration can be expressed either qualitatively or quantitatively. For example, qualitatively we can say that the solution is dilute (i.e., a relatively very small quantity of solute) or it is concentrated (i.e., a relatively very large quantity of solute). But in reality, the qualitative description can confuse, and hence there is a need for a quantitative description of the solution.

There are several ways by which we can describe the concentration of the solution quantitatively.

(1) Mass percentage (w/w):

It is the mass of any component present in 100 g of solution.

Mathematically, it can be defined as:

Mass $\%$ of a component $=\frac{\text { Mass of the component in the solution }}{\text { Total mass of the solution }} \times 100$

For example, a solution described as 20% by mass of glucose in water, it means that 20 g of glucose is dissolved in 80 g of water resulting in a 100 g solution.

The mass % can also be expressed in terms of the mass fraction by simply removing the 100 from the above-given formula

Concentration described by mass percentage is commonly used in industrial chemical applications.

(2) Volume percentage (V/V):

It is the volume of any solute present in 100 ml of the solution. Mathematically it is defined as:

Volume $\%$ of a component $=\frac{\text { Volume of the component }}{\text { Total volume of solution }} \times 100$

For example, a 20% Methanol solution in water means that 20 mL of Methanol is dissolved in water such that the total volume of the solution is 100 mL. Solutions containing liquids are commonly expressed in this unit.

(3) Mass by volume percentage (w/V):

It is the mass of solute dissolved in 100 mL of the solution. Mathematically, it is defined as:

Mass by Volume $\%$ of a component $=\frac{\text { Mass of the component }}{\text { Total volume of solution }} \times 100$

For example, a 20% weight-by-volume solution of Glucose in water means that 20 g of Glucose was dissolved in water to obtain a 100ml solution.

This concentration term is commonly used in medicine and pharmacy.

(4) Parts per million (ppm):

When a solute is present in trace quantities, it is convenient to express concentration in parts per million (ppm) and is defined as: Parts per million $=\frac{\text { Number of parts of the component }}{\text { Total number of parts of all components of the solution }} \times 10^6$

As in the case of percentage, concentration in parts per million can also be expressed as mass to mass, volume to volume, and mass to volume.

This is generally used in expressing the hardness of water and in expressing the concentration of dissolved oxygen in water etc.

For example, if the hardness of a hard water sample is 100pm in CaCO₃, it means that 100 g of CaCO₃ is present in 10⁶ g of the water sample.

(5) Mole fraction:

It is the ratio of the moles of any component present in the solution to the total moles present in the solution. A commonly used symbol for mole fraction is X and the subscript used on the right-hand side of X denotes the component.

It is defined as: Mole fraction of a component $=\frac{\text { Number of moles of the component }}{\text { Total number of moles of all the components }}$

For example, in a binary mixture, if the number of moles of A and B is n_A and n_B respectively, the mole fraction of A will be:

$\mathrm{x}_{\mathrm{i}}=\frac{\mathrm{n}_1}{\mathrm{n}_1+\mathrm{n}_2+\ldots \ldots+\mathrm{n}_{\mathrm{i}}}=\frac{\mathrm{n}_{\mathrm{i}}}{\sum \mathrm{n}_{\mathrm{i}}}$

It can be shown that in a given solution sum of all the mole fractions is unity, i.e.

$x_1+x_2+\ldots \ldots \ldots \ldots \ldots+x_i=1$

Mole fraction unit is very useful in relating some physical properties of solutions, say vapor pressure with the concentration of the solution, and quite useful in describing the calculations involving gas mixtures.

(6) Molality(m):

It is defined as the number of moles of the solute present per kilogram (kg) of the solvent and is expressed as:

$\operatorname{Molality}(\mathrm{m})=\frac{\text { Moles of solute }}{\text { Mass of solvent in } \mathrm{kg}}$

For example, 1 molal solution of NaOH means that 1 mol (40 g) of NaOH is dissolved in 1 kg of water.

(7) Molarity (M):

It is defined as the number of moles of solute dissolved in one liter of solution

Molarity $=\frac{\text { Moles of solute }}{\text { Volume of solution in litre }}$

For example, 0.5 mol L^-1 (or 0.5 M) solution of NaOH means that there is 0.5 mol of NaOH dissolved in water to obtain one liter of solution.

Each method of expressing the concentration of the solutions has its own merits and demerits. Mass %, ppm, mole fraction, and molality are independent of temperature, whereas molarity is a function of temperature. This is because volume depends on temperature and mass does not.

Recommended topic video on (Types of Solutions)

Some Solved Examples

Example.1

1. Which of the following is the correct combination of the dispersed phase and dispersion medium, among the colloids cheese (C), milk (M) and smoke (S)?

1) (correct)C: liquid in solid; M: liquid in liquid; S : solid in gas

2)C: liquid in solid; M: liquid in solid; S: solid in gas

3)C: solid in liquid; M: solid in liquid; S: solid in gas

4)None of the above

Solution

Solutions - A homogeneous mixture of solute and solvent is present in the same phase.

Eg. NaCl in H₂O

Nature of liquid and vapor pressure -

More volatile liquids exert more vapour pressure.

More volatile liquids are those when intermolecular forces are weak.

Cheese-liquid in solid

Milk -liquid in the liquid

Smoke - Solid in gas
Hence, the answer is the option (1).

Example.2

2. Among the colloids cheese (C), milk (M) and smoke (S), the correct combination of the dispersed phase and dispersion medium, respectively is :

1)C: liquid in solid; M: liquid in solid; S: solid in gas

2) (correct)C: liquid in solid; M: liquid in liquid; S: solid in gas

3)C: solid in liquid; M: Liquid in Liquid; S: gas in solid

4)C: solid in liquid; M: solid in liquid; S: solid in gas

Solution

Cheese-liquid in solid

Milk -liquid in the liquid

Smoke - Solid in gas

Hence, the answer is the option (2).

Example.3

3. Which statement best explains the meaning of the phrase “like dissolves like“?

1)A Solute will easily dissolve a solute of similar mass

2) (correct)A solvent and solute with similar intermolecular forces will readily form a solution

3)The only true solutions are formed when water dissolves a non-polar solute

4)The only true solutions are formed when water dissolves a polar solute

Solution

To form a solution, the nature of intermolecular forces in solute and solvent should be the same. Polar solutes dissolve in polar solvents and non-polar solutes dissolve in non-polar solvents.

Hence, the answer is an option (2).

Example.4

4. Select the correct statement out of the following regarding a binary solution

1) The component which is present in excess is solute

2) (correct)The component which is present in excess is the solvent

3)In a solution, the physical state of the solute is retained.

4)In a solution, the physical state of the solvent is not retained.

Solution

Answer : (2) In a solution , the species which is present in the same state as the solution is the solvent . In case both species are in the same physical state , then the species present in excess is the solvent .

Example.5

5. In Brine, which is a solution containing NaCl and water, and in hydrated Copper Sulphate respectively, the solvents are

1)Water and Water

2)NaCl and $\mathrm{CuSO}_4$

3) (correct)Water and $\mathrm{CuSO}_4$

4)NaCl and Water

Solution

Answer : (3) In Brine, water is present in excess while in $\mathrm{CuSO}_4 \cdot 5 \mathrm{H}_2 \mathrm{O}$ , the physical state of the solution is Solid, hence the solvent is CuSO₄

Summary

Solutions are integral to numerous fields and applications, from daily life and industrial processes to scientific research and environmental management. Their ability to provide uniform mixtures and facilitate various reactions makes them essential for both practical uses and academic study. Solutions are of various types which include various types of substances such as solid sol, which includes Alloys eg bronze, and steel, liquid sol includes salt water and sugar dissolved in water and the other one is gaseous solution which includes air a mixture of gaseous like oxygen, nitrogen and carbon dioxide. Solutions have so many applications such as Medicine: Solutions are used in intravenous fluids and medications. For example, saline solutions help in hydration and electrolyte balance.