Solutions - Introduction and Types of solutions Class 12 Notes | EduRev

What is a Solution?

• A solution is a homogeneous mixture of two or more components in which the particle size is smaller than 1 nm.
• Common examples of solutions are sugar in water and salt in water solutions, soda water, etc. In a solution, all the components appear as a single phase. There is particle homogeneity i.e. particles are evenly distributed. This is why a whole bottle of soft drink has the same taste throughout.

Solute and Solvent

• Solvent: The substance which is present in the largest quantity in a solution; is generally referred to as a solvent.
  Example: In the solution of salt in water, since water is present in larger quantity, thus, water is called the solvent. It is the solvent that decides the phase of a solution.
• Solute: The substance which is present in lesser quantity in a solution is generally called the solute.
  In other words, one or more components present in a solution other than the solvent are is called the solute.
  Example: In the solution of salt in water, salt is called the solute. The solute may be more than one.

Note: Physical state of solvent and solution is same.

Different Types of Solutions 

1. Binary Solution

Solutions which contain only two components are called a binary solution. For example, a solution of salt in water is a type of binary solution, as it contains only two components.

Binary Solution = Solute + Solvent

Similarly, it is called ternary and quaternary if it is composed of three and four components, respectively.
Thus; a solution may be regarded as a single-phase containing more than one component.

2. Dilute Solution

A solution in which relatively a small amount of solute is dissolved in a large amount of solvent is called a dilute solution.

3. Concentrated Solution

A solution in which relatively a large amount of the solute is present is called a concentrated solution.

Properties of a Solution

• A solution consists of a single-phase i.e. it is a monophasic system.
• A solution is a uniform throughout, such as uniform properties such as density, refractive index, etc.
• The components of a solution cannot be easily separated by physical methods.
• The composition of a solution is not definite but can vary within certain limits.
• Certain properties of solution such as density, viscosity, surface tension, boiling point, freezing point etc. vary with the composition of the solution.

Table: Types of Solution

In a solution, components may be solid, liquid or gas. 

Gaseous, Liquid & Solid Solutions 

1. Gaseous Solution

Solutions in which solvent is present is a gaseous state is called Gaseous solution. 

Gaseous solutions can be divided into following three types on the basis of phases of solute and solvent;

1. Gas - Gas Solution: Solutions in which solute and solvent both are gases; are called Gas-gas Solutions.
   Example: solution (mixture) of nitrogen and oxygen, solution (mixture) of carbon dioxide and nitrogen, solution (mixture) of carbon dioxide and oxygen, etc.
2. Liquid Gas Solution: Solutions, in which solute is in a liquid state and solvent is in a gaseous state, are called Liquid-Gas Solution.
   Example: solution (mixture) of chloroform in nitrogen gas.
3. Solid Gas Solution: Solutions, in which solute is in solid-state and solvent is in a gaseous state, are called Solid-Gas Solutions.
   Example: Solution (mixture) of camphor in nitrogen gas.

2. Liquid Solution

Solutions, in which solvent is present in a liquid state, are called Liquid solutions. 

Liquid solutions can be classified into the following three types:

1. Gas-Liquid Solution: Solutions having solute in gaseous state and solvent in the liquid state are called Gas-Liquid Solutions.
   Example: Solution (mixture) of oxygen in water, a mixture of carbon dioxide in water. Coca-cola, a beverage, is an example of a gas-liquid solution, as it has carbon dioxide dissolved in water.
2. Liquid - Liquid Solution: Solutions, in which solute and solvent both are present in a liquid state, are called liquid liquid solutions.
   Example: Vinegar solution, vinegar is the mixture of ethanoic acid and water. Solution of ethanol in water, etc.
3. Solid-Liquid Solution: Solutions, in which solutes present in solid-state and solvent is in a liquid state, are called solid-liquid solutions.
   Example: Solution of salt in water, solution of glucose in water, etc.

3. Solid Solution

Solutions having solvent in the solid-state, are called solid solutions. 

The solid solution can be divided into the following three categories:

1. Gas-Solid Solution: Solutions having solvent in solid-state and solute in the gaseous state are called gas-solid solutions.
   Example: solution of hydrogen in palladium.
2. Liquid-Solid Solution: Solutions having solvent in solid-state and solute in the liquid state are called liquid-solid solutions.
   Example: an amalgam of mercury with sodium.
3. Solid-solid solution: Solutions having solvent and solute both in the solid-state are called solid-solid solutions.
   Example: Solution of gold and copper.

What are Mixtures? 

• When two or more chemically non-reacting substances are mixed, they form mixtures. A mixture may be heterogeneous or homogeneous. 
• A heterogeneous mixture consists of distinct phases and the observed properties are just the sum of the properties of individual phases. However, a homogeneous mixture consists of a single-phase which has properties that may differ drastically from those of the individual components.
• A homogeneous mixture whose composition can·be varied within certain limits is termed a true solution. 
• The constituents of a solution cannot be separated by filtration, settling or centrifugal action. All solutions are characterised by
  (i) Homogeneity
  (ii) Absence of settling
  (iii) The molecular or ionic state of sub-division of the components. When the solution is composed of only two chemical substances, it is termed a binary solution.
• Similarly, it is called ternary and quaternary if it is composed of three and four . components, respectively. thus; a solution may be regarded as a single phase containing more than one component.  

Example

• A mixture of salt and sugar.
• A mixture of oxygen and nitrogen.
• A mixture of sugar in water.

Homogeneous and Heterogeneous Mixture

1. Homogeneous Mixture: A mixture of two or more components having no distinguish phase is called a homogeneous mixture. 
   The homogeneous mixture is generally referred to as a solution. 
   Example: When two spoons of salt are mixed in a glass of water, the mixture so obtained has no distinguish phase and this is called a solution. 
   
   Solution
   
   Air is a mixture of different gases with no distinguish phase, thus, the air is often referred to as the solution.
   In a homogeneous mixture, i.e. solution, the composition, and properties of the solution are uniform throughout.
2. Heterogeneous Mixture: A mixture of two or more components with distinguish phase is called a heterogeneous mixture.
   Example: A mixture of mustard oil and water, in this mixture phases of water and mustard oil, can be seen and distinguished clearly, and hence called heterogeneous mixture.

Heterogeneous Mixture: Oil and Water

Frequently Asked Questions (FAQs)

Q1. What are the components of solution?

Ans: Solutions are made up of two parts: a solvent and a solute.
Solvent: The component that dissolves the other component is called the solvent.
Solute: The component that is dissolved in the solvent is called solute.

Q2. What are some common examples of mixtures and solutions?
Ans: Air is a homogeneous mixture that contains oxygen, nitrogen, argon and other gases; iron filings with sulfur powder is a commonly used heterogeneous mixture; salty water is a solution that contains particles of salt mixed with particles of water.

Q3. Is coffee a mixture?
Ans: Coffee is a solution, not a compound or mixture, as it includes a solute that dissolves into a solvent. At times, coffee can also be considered a mixture since it involves two mixed substances, but this is too vague.

Q4. Is chocolate a mixture?
Ans: Chocolate is a solid mixture. In its basic form it is composed of cacao powder, cocoa butter, and some type of sweetener such as sugar; however, modern chocolate includes milk solids, any added flavors, modifiers, and preservatives.

Q5. Are eggs a mixture?
Ans: An egg is neither a pure substance nor a mixture. If you crack open an egg, you see eggshells, egg whites, and egg yolks. This means that even macroscopically, an egg is not a mixture, it is an unmixed combination of egg shell, egg white, and egg yolk.