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Chemistry · Class 12 Science

Ch 1Liquid State — Class 12 Chemistry, concept-first.

A liquid solution is a homogeneous mixture in which one or more substances (the solutes) are dispersed, at the molecular or ionic level, throughout a liquid (the solvent), so that the composition and every measurable property are the same in every part of the mixture.

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Key concepts

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Henry's Law and Gas Solubility

Henry's law describes the equilibrium reached when a gas dissolves in a liquid: at a fixed temperature, the amount of gas dissolved is directly proportional to the partial pressure of that gas maintained above the liquid…

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Chapter contents

The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.

1.1

Introduction to Liquid Solutions

A liquid solution is a homogeneous mixture in which one or more substances (the solutes) are dispersed, at the molecular or ionic level, throughout a liquid (the solvent), so that the composition and…

1.2

Solubility of Gases in Liquids: Henry's Law

When a gas is brought into contact with a liquid, some of it dissolves until the rate at which gas molecules enter the liquid equals the rate at which dissolved molecules escape back into the gas phas…

1.3

Solid Solutions

Solid solutions are homogeneous solid mixtures formed when one solid substance (the solute) is dissolved throughout the crystal lattice of another (the solvent), producing a single solid phase with pr…

1.4

Vapour Pressure of Liquid Solutions and Raoult's Law

When two volatile liquids, A and B, are mixed to form a solution, both components contribute molecules to the vapour above the liquid, and the composition of that vapour is governed by Raoult's law.

1.5

Raoult's Law as a Special Case of Henry's Law; Ideal Solutions

Raoult's law for a volatile solute, , and Henry's law for a dissolved gas, , look different at first glance but are in fact the same underlying relationship, differing only in the value taken by the p…

1.6

Non-Ideal Solutions: Positive and Negative Deviations from Raoult's Law

Most real liquid-liquid solutions do not obey Raoult's law exactly across their whole composition range; instead, their actual total vapour pressure deviates either above or below the value Raoult's l…

1.7

Colligative Properties and Relative Lowering of Vapour Pressure

Colligative properties are those properties of a solution that depend solely on the number of solute particles dissolved in a given quantity of solvent, and not at all on the chemical nature of those…

1.8

Elevation of Boiling Point

A liquid boils, at any given external pressure, at exactly the temperature at which its vapour pressure becomes equal to that external pressure.

1.9

Depression of Freezing Point

Exactly the same reasoning that explains boiling-point elevation also explains the depression of freezing point, but applied to the equilibrium between solid solvent and liquid solvent instead of betw…

1.10

Osmosis and Osmotic Pressure

A semipermeable membrane is a barrier — natural (a cell membrane, an animal bladder) or artificial (a parchment or cellophane film) — with pores fine enough to let small solvent molecules pass freely…

1.11

Determination of Molecular Mass Using Colligative Properties

All four colligative properties covered in this chapter — relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, and osmotic pressure — can, in principle, each…

1.12

Abnormal Molar Mass and van't Hoff Factor

The molar mass calculated from a measured colligative property occasionally disagrees, sometimes quite dramatically, with the molar mass expected from the solute's known chemical formula — a discrepan…

1.13

True Solutions, Colloids and Suspensions

Not every mixture of two substances is a true solution. Depending chiefly on the size of the particles of one substance dispersed through the other, a two-component mixture falls into one of three bro…

1.14

Classification of Colloids: Lyophilic, Lyophobic, Multi-molecular, Macromolecular and Associated Colloids

Colloids are classified along two entirely independent lines: how strongly the dispersed phase interacts with, and is attracted to, the dispersion medium, and how the individual colloidal particles ar…

1.15

Properties of Colloids: Tyndall Effect, Brownian Movement and Electrophoresis

Three characteristic physical properties, taken together, provide direct experimental evidence for the size, ceaseless motion, and electric charge of colloidal particles.

1.16

Coagulation of Colloids and Emulsions

A lyophobic sol is only kinetically stable, not thermodynamically stable, precisely because its particles carry a like electric charge that keeps them electrostatically repelled from one another; deli…

Summary

This chapter developed the Liquid State unit of the WBCHSE Class XII Chemistry syllabus in two connected stages.

Sample & Board Papers

Sample papers and previous-year board questions for this subject.

+Show 14 questions14 questions
  1. Q1Two solutions are isotonic. What is meant by the statement? **OR** When a little amount of common salt is dissolved in water, the boiling po…Preview
  2. Q2What is meant by the molality of a solution? What would be the osmotic pressure of a 0.02 molar aqueous solution of urea at 27°C? (R = 0.082…Preview
  3. Q3KBr undergoes 80% dissociation in its 0.5 (M) aqueous solution. Calculate osmotic pressure of the solution at 27°C temperature. **OR** What…Preview
  4. Q4(i) What is the vapour pressure of pure water at 100°C temperature? (1 mark) (ii) 12 gm of a solid solute is dissolved in 90 gm pure water.…Preview
  5. Q5(i) Vapour pressure of a pure solvent decreases when non-volatile solid solute is added to it. Explain why. (ii) State the Raoult's law of r…Preview
  6. Q6(i) What is van't Hoff factor? (ii) 36 g of glucose dissolved per litre of the solution has an osmotic pressure 4.98 bar at 300 K. If the os…Preview
  7. Q7Which of the following solutions has the lowest freezing point? (a) 1 (m) sucrose (b) 1 (m) KCl (c) 1 (m) MgCl2 (d) 1 (m) glucosePreview
  8. Q8Which of the following gases does not obey Henry's law? (a) O2 (b) H2 (c) N2 (d) NH3Preview
  9. Q9Lyophobic sol can be protected / stabilised by (a) Boiling (b) Addition of electrolyte (c) Addition of coagulating agent (d) Addition of lyo…Preview
  10. Q10Which one of the following does not involve coagulation? (a) Use of NaCl to stop bleeding (b) Formation of delta (c) Peptization (d) Treatme…Preview
  11. Q11If the elevation in boiling point of a solution of 10 g of non-volatile, non-dissociative, non-associative solute in 100 g of water is dTb a…Preview
  12. Q12Fog is a colloidal solution of (a) Solid in gas (b) Gas in gas (c) Liquid in gas (d) Gas in liquidPreview
  13. Q13At a given temperature aqueous solution of 0.1 (M) KNO3 is isotonic with aqueous solution of sucrose. What is the concentration of the solut…Preview
  14. Q14The process of transformation of a freshly prepared precipitate into colloidal solution by adding a suitable electrolyte is called (a) Dialy…Preview

More questions

36 Q
+Show 20 questions20 questions
  1. Example 1State Henry's law for the solubility of a gas in a liquid, and write its mathematical form relating the partial pressure of the gas above th…Free
  2. Example 2The partial pressure of $\text{CO}_2$ gas maintained above a bottle of soft drink at $298\ \text{K}$ is $4\ \text{bar}$. If the Henry's law…Free
  3. Example 3At $298\ \text{K}$, the Henry's law constant for oxygen gas dissolved in water is $K_H = 4.259 \times 10^4\ \text{bar}$. Calculate the mole…Free
  4. Example 4Using Henry's law and the fact that dissolution of a gas in a liquid is an exothermic process, explain why the solubility of a gas in a liqu…Preview
  5. Example 5Differentiate between a substitutional solid solution and an interstitial solid solution, giving one metallurgical example of each.Preview
  6. Example 6Classify each of the following as a substitutional or an interstitial solid solution, with a reason: (a) brass, in which zinc atoms replace…Preview
  7. Example 7At $293\ \text{K}$, the vapour pressure of pure benzene is $74.66\ \text{mm Hg}$ and that of pure toluene is $22.31\ \text{mm Hg}$. A soluti…Preview
  8. Example 8A solution of acetone and chloroform shows a negative deviation from Raoult's law, while a solution of ethanol and acetone shows a positive…Preview
  9. Example 9$6\ \text{g}$ of urea ($M = 60\ \text{g mol}^{-1}$) is dissolved in $180\ \text{g}$ of water at $298\ \text{K}$. Calculate the relative lowe…Preview
  10. Example 10The vapour pressure of pure water at $298\ \text{K}$ is $23.8\ \text{mm Hg}$. Using the relative lowering of vapour pressure found for the u…Preview
  11. Example 11Calculate the elevation in boiling point when $3.6\ \text{g}$ of glucose ($M = 180\ \text{g mol}^{-1}$) is dissolved in $250\ \text{g}$ of w…Preview
  12. Example 12$2.5\ \text{g}$ of a non-volatile, non-electrolyte solute is dissolved in $100\ \text{g}$ of water. The boiling point of the resulting solut…Preview
  13. Example 13$1.00\ \text{g}$ of a non-electrolyte solute is dissolved in $50\ \text{g}$ of benzene. The freezing point of benzene is lowered by $0.40\ \…Preview
  14. Example 14Calculate the depression in freezing point of a solution containing $34.2\ \text{g}$ of sucrose ($M = 342\ \text{g mol}^{-1}$) dissolved in…Preview
  15. Example 15Calculate the depression in freezing point produced by dissolving $1.00\ \text{g}$ of glucose ($M = 180\ \text{g mol}^{-1}$) in $50\ \text{g…Preview
  16. Example 16$1.0\ \text{g}$ of a non-volatile, non-electrolyte solute of molar mass $60\ \text{g mol}^{-1}$ is dissolved in enough water to make $200\ \…Preview
  17. Example 17$200\ \text{mL}$ of an aqueous solution of a protein contains $1.26\ \text{g}$ of the protein. The osmotic pressure of this solution at $300…Preview
  18. Example 18$0.6\ \text{mol}$ of $\text{NaCl}$ is dissolved in $1\ \text{kg}$ of water. Assuming $\text{NaCl}$ dissociates completely into its ions, cal…Preview
  19. Example 19A $0.1\ \text{mol kg}^{-1}$ aqueous solution of $\text{KCl}$ shows a freezing-point depression of $0.372\ \text{K}$, rather than the $0.186\…Preview
  20. Example 20Acetic acid ($M = 60\ \text{g mol}^{-1}$) is known to dimerize partially in benzene solution. If the molar mass of acetic acid measured by f…Preview
+Show 16 questions16 questions
  1. Q21Define the term colloid, and distinguish between a true solution, a colloidal solution and a suspension on the basis of the approximate size…Free
  2. Q22Classify colloids as lyophilic or lyophobic, and give one example of each along with one key difference in their stability.Free
  3. Q23Explain, with one example each, what is meant by a multi-molecular colloid, a macromolecular colloid, and an associated colloid (micelle).Free
  4. Q24Explain what the Tyndall effect is, and explain why it is observed when a beam of light is passed through a colloidal solution but not when…Preview
  5. Q25Explain Brownian movement, state its physical cause, and explain how it contributes to the stability of a colloidal solution against settlin…Preview
  6. Q26Explain what electrophoresis demonstrates about colloidal particles. In an electrophoresis experiment, a freshly prepared $\text{Fe(OH)}_3$…Preview
  7. Q27Explain what is meant by coagulation of a colloidal sol, and state the Hardy–Schulze rule. For the coagulation of a negatively charged $\tex…Preview
  8. Q28Define an emulsion, and distinguish between an oil-in-water (o/w) and a water-in-oil (w/o) emulsion. Classify each of the following as o/w o…Preview
  9. Q29Explain the role of an emulsifying agent in stabilizing an emulsion, and explain, with soap as the emulsifier, why soap stabilizes an oil-in…Preview
  10. Q30The mole fraction of a gas dissolved in water at $298\ \text{K}$ and a partial pressure of $1\ \text{bar}$ is found to be $2 \times 10^{-5}$…Preview
  11. Q31$18\ \text{g}$ of glucose ($M = 180\ \text{g mol}^{-1}$) is dissolved in $178.2\ \text{g}$ of water. If the vapour pressure of pure water at…Preview
  12. Q32$5\ \text{g}$ of $\text{Na}_2\text{SO}_4$ ($M = 142\ \text{g mol}^{-1}$) is dissolved in $100\ \text{g}$ of water. Assuming $\text{Na}_2\tex…Preview
  13. Q33$0.1\ \text{mol}$ of $\text{MgCl}_2$ is dissolved in $1\ \text{kg}$ of water. Assuming complete dissociation into three ions, calculate the…Preview
  14. Q34Explain what it means for two solutions to be isotonic, and explain, using osmosis, why an intravenous fluid given to a patient must be isot…Preview
  15. Q35A solution containing $7.5\ \text{g}$ of a non-volatile, non-electrolyte solute in $250\ \text{mL}$ of solution has an osmotic pressure of $…Preview
  16. Q36$0.30\ \text{g}$ of benzoic acid ($M = 122\ \text{g mol}^{-1}$) is dissolved in $30\ \text{g}$ of benzene. The observed depression in freezi…Preview