Solutions

NCERT Exercise solution Q: 1-3

Question : 2.1 – Define the term solution. How many types of solutions are formed? Write briefly about each type with an example.

Answer:

Soution: Solution is the homogeneous mixture of two or more components.

Example – mixture of salt and sugar, mixture of oxygen and nitrogen, mixture of sugar in water, etc.

Types of solution: In a solution, components (solute and solvent) may be solid, liquid or gas. On the basis of physical state of solvent, solutions can be divided into following three types:

1. Gaseous solutions
2. Liquid solutions
3. Solid solutions

(a) Gaseous solution: Solutions in which solvent is gas is called gaseous solution. For example – air. Air is a mixture of many gases, such as oxygen, nitrogen, carbon dioxide, etc.

Gasesous solution can be further classified into three types – they are

• Gas in gas (gas-gas) solution,
• Liquid in gas (liquid-gas) solution and
• Solid in gas (solid-gas) solution.

(b) Liquid solutions: Solutions in which solvent is liquid is called liquid solution. For example – solution of salt and water, solution of methanol in water.

Liquid solutions further can be divided into three types – viz.

• Solid in liquid (solid-liquid) solution,
• Liquid in liquid (liquid-liquid) solution and
• Gas in liquid (gas- liquid) solution.

(c) Solid solution: Solutions in which solvent is solid is called solid solution. For example – Alloys, hydrated salt, etc.

Solid solution can be further divided into three types – viz.

• Solid in solid (solid-solid) solution,
• Liquid in solid (liquid-solid) solution and
• Gas in solid (gas-solid) solution.

Question: 2.2 – Give an example of a solid solution in which the solute is gas.

Answer: Solution of hydrogen and palladium. In this hydrogen which is a gas is solute and palladium is solvent.

Question: 2.3 – Define the following: Mole fraction Molality Molarity Mass percentage

Answer:

(i) Mole fraction –Mole fraction is a way to express concentration of a solution.

Mole fraction of a constituent (either of solute or solvent) is the ratio of number of moles of one component to the total number of moles of all component present in a solution.

Mole fraction is denoted by letter, ‘x’.

(ii) Molality: Molality is a way to express concentration of solution.

(iii) Molarity:

(iv) Mass percentage

Mass % of component =

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