# Solutions Notes, Class 12 Chemistry | SwaVid

Solutions: NCERT Class 12 Chemistry notes with key ideas, formulas, common mistakes and 3 quick checks with worked answers. Written by SwaVid from the textbook.

Canonical: https://www.swavid.com/cbse/class-12/chemistry/chapter/solutions

Source: https://www.swavid.com/cbse/class-12/chemistry/chapter/solutions

# Solutions

## Formulas and definitions

## Key ideas

## Common mistakes

## Quick checks

## Keep going

## Questions parents ask

## Class 12 Chemistry on SwaVid

### Types of solutions and concentration

### Solubility and Henry's law

### Vapour pressure and Raoult's law

### Colligative properties

### Abnormal molar mass and van 't Hoff factor

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SwaVid › CBSE › Class 12 › Chemistry › Solutions

Notes written by SwaVid from the NCERT textbook.

Class 12 Chemistry, Unit 1. Key ideas, formulas and common mistakes.

CBSE prints 7 marks for Unit 1, not for this chapter alone.

Short answer. This chapter deals with binary solutions, their concentration terms, and the solubility of gases and solids in liquids. It explains vapour pressure through Raoult's law, colligative properties, and abnormal molar masses using the van 't Hoff factor.

Source: NCERT Chemistry Part I (Reprint 2026-27) , Unit 1, Solutions

Solutions are homogeneous mixtures of two or more components. Common concentration terms include mass percentage, volume percentage, parts per million, mole fraction, molarity, and molality. Molality and mole fraction do not change with temperature because they depend only on mass.

The solubility of a solid in a liquid usually increases with rising temperature if the process is endothermic. For a gas dissolved in a liquid, Henry's law states that the partial pressure of the gas is directly proportional to its mole fraction in the solution. Gas solubility decreases as temperature increases.

Raoult's law states that for a solution of volatile liquids, the partial vapour pressure of each component is equal to its vapour pressure in pure state multiplied by its mole fraction. Ideal solutions obey Raoult's law over the entire range of concentration, having Δ mix H = 0 and Δ mix V = 0. Non-ideal solutions show positive or negative deviations and form azeotropes.

Colligative properties depend only on the number of solute particles, not on their nature. These properties are relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, and osmotic pressure. They are used to calculate the molar mass of non-volatile solutes.

When a solute undergoes dissociation or association in solution, its observed colligative property differs from the normal value. The van 't Hoff factor i accounts for this change. Values of i greater than 1 indicate dissociation, while values less than 1 indicate association.

Try each question first. Then tap it to see the answer.

Moles of ethanoic acid = 2.5 / 60 = 0.0417 mol

Mass of benzene in kg = 75 / 1000 = 0.075 kg

Molality = 0.0417 / 0.075 = 0.556 mol kg⁻¹

0.556 mol kg⁻¹

Moles of urea n₂ = 30 / 60 = 0.5 mol

Moles of water n₁ = 855 / 18 = 47.5 mol

Mole fraction of solute x₂ = 0.5 / (47.5 + 0.5) = 0.5 / 48 = 0.0104

(p₁° - p₁) / p₁° = x₂ → p₁ = 23.8 × (1 - 0.0104) = 23.8 × 0.9896 = 23.55 mm Hg

23.55 mm Hg

M₂ = (1000 × K f × w₂) / (ΔT f × w₁)

M₂ = (1000 × 5.12 × 1.00) / (0.40 × 50)

M₂ = 5120 / 20 = 256 g mol⁻¹

256 g mol⁻¹

Electrochemistry .

Chemical Kinetics .

The 10 chapters of Class 12 Chemistry .

CBSE does not give marks to one chapter. It prints 7 marks for Unit 1, Solutions, which includes Solutions.

No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed.

Electrochemistry.

SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works.

- Unit 1 NCERT book
- 7 marks, Unit 1
- 3 quick checks
- Using volume of solution instead of mass of solvent when calculating molality . Molality has mass of solvent in kilograms in the denominator. Molarity uses the total volume of solution in litres.
- Forgetting the van 't Hoff factor for electrolytes in colligative property formulas . Check whether the solute dissociates or associates in the solvent. Multiply K b × m, K f × m, or CRT by i whenever an electrolyte is present.
- Confusing temperature differences in Celsius and Kelvin . A change in temperature ΔT has the exact same numerical value in Kelvin as in degrees Celsius. Do not add 273.15 to a temperature difference.
- Using Henry's constant K H without checking its pressure units . K H shares the units of pressure (such as bar or Pa). Match the unit of partial pressure p directly with the given unit of K H .

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