CLASS 12 CHEMISTRY
CHAPTER: SOLUTIONS
Student-Friendly • Concept + Formula + Numericals + Exam Revision
NCERT-aligned study notes
Class 12 Chemistry — Solutions | Page 1
, 1. Introduction to Solutions
Solution is a homogeneous mixture of two or more components. The component present in larger amount is usually called
the solvent, while the component present in smaller amount is the solute.
Example: In a salt-water solution, water is the solvent and salt is the solute.
Types: Solutions can involve solid, liquid or gaseous solutes and solvents. Examples include air (gas in gas), soda water
(gas in liquid), alcohol in water (liquid in liquid), and brass (solid in solid).
2. Concentration of Solutions
Concentration tells us how much solute is present in a given amount of solution or solvent.
(a) Mass percentage = (Mass of solute / Mass of solution) × 100
Example: 10 g NaCl + 90 g water gives 10 g solute in 100 g solution, so mass % = 10%.
(b) Volume percentage = (Volume of solute / Volume of solution) × 100
(c) Mass by volume % = (Mass of solute in g / Volume of solution in mL) × 100
(d) Parts per million (ppm) = (Number of parts of component / Total parts of solution) × 106. It is useful for very dilute
solutions.
(e) Mole fraction: xA = nA/(nA+nB). For a binary solution, xA + xB = 1.
(f) Molarity (M) = moles of solute / volume of solution in litres. Molarity changes with temperature because volume can
change.
(g) Molality (m) = moles of solute / mass of solvent in kg. Molality is temperature-independent because mass does not
change with temperature.
Class 12 Chemistry — Solutions | Page 2
CHAPTER: SOLUTIONS
Student-Friendly • Concept + Formula + Numericals + Exam Revision
NCERT-aligned study notes
Class 12 Chemistry — Solutions | Page 1
, 1. Introduction to Solutions
Solution is a homogeneous mixture of two or more components. The component present in larger amount is usually called
the solvent, while the component present in smaller amount is the solute.
Example: In a salt-water solution, water is the solvent and salt is the solute.
Types: Solutions can involve solid, liquid or gaseous solutes and solvents. Examples include air (gas in gas), soda water
(gas in liquid), alcohol in water (liquid in liquid), and brass (solid in solid).
2. Concentration of Solutions
Concentration tells us how much solute is present in a given amount of solution or solvent.
(a) Mass percentage = (Mass of solute / Mass of solution) × 100
Example: 10 g NaCl + 90 g water gives 10 g solute in 100 g solution, so mass % = 10%.
(b) Volume percentage = (Volume of solute / Volume of solution) × 100
(c) Mass by volume % = (Mass of solute in g / Volume of solution in mL) × 100
(d) Parts per million (ppm) = (Number of parts of component / Total parts of solution) × 106. It is useful for very dilute
solutions.
(e) Mole fraction: xA = nA/(nA+nB). For a binary solution, xA + xB = 1.
(f) Molarity (M) = moles of solute / volume of solution in litres. Molarity changes with temperature because volume can
change.
(g) Molality (m) = moles of solute / mass of solvent in kg. Molality is temperature-independent because mass does not
change with temperature.
Class 12 Chemistry — Solutions | Page 2
