What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

What is meant by dynamic equilibrium?

A condition in which forward and reverse reactions proceed simultaneously at equal rates, keeping observable properties constant.

The mass of a gas dissolved in a given mass of solvent at constant temperature is proportional to the pressure of the gas above it.

State the law of mass action.

For \(aA+bB\rightleftharpoons cC+dD\), \(K_c=[C]^c[D]^d/[A]^a[B]^b\) is constant at a given temperature.

What is the relation between \(K_p\) and \(K_c\)?

\(K_p=K_c(RT)^{\Delta n}\), where \(\Delta n\) is moles of gaseous products minus gaseous reactants.

How does the reaction quotient predict direction?

If \(Q K\) it proceeds backward, and if \(Q=K\) it is at equilibrium.

Does a catalyst change the position of equilibrium?

No; it speeds the forward and reverse reactions equally and only helps equilibrium be reached faster.

How does temperature affect \(K\) of an exothermic reaction?

Raising the temperature decreases \(K\), shifting the equilibrium toward reactants.

Distinguish Arrhenius, Brønsted and Lewis acids.

An Arrhenius acid gives \(H^+\) in water, a Brønsted acid donates a proton, and a Lewis acid accepts an electron pair.

The negative logarithm of the hydrogen-ion concentration, \(pH=-\log[H^+]\).

What is a buffer solution?

A solution that resists changes in pH on adding small amounts of acid or base, usually a weak acid with its salt or a weak base with its salt.

Equilibrium

Class 11 Chemistry · Chemistry Part I · Chapter 6

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CBSE Class 11 · Chemistry

Chemistry Part I: 45 of 70 theory marks

Marks booster + cheatsheet: key concepts in 2 lines each, common traps
9 marks each: Atom and Thermodynamics
Constants and formulas, with page numbers
Common traps, corrected
Periodic trends from the real data
pH, buffers and solubility product

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CBSE Class 11 · Chemistry

Organic basics: 11 marks, the biggest unit

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10 marks: Hydrocarbons
Every reaction with reagent and condition
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Oxidation-number rules and balancing

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Summary

This unit develops the idea of equilibrium for both physical and chemical systems. Physical equilibria — solid-liquid, liquid-vapour, solid-vapour and the dissolution of solids and gases in liquids (Henry's law) — are dynamic, with opposing processes proceeding at equal rates in a closed system so that measurable properties stay constant. Chemical equilibrium is likewise dynamic, demonstrated by the Haber synthesis of ammonia and by isotope-scrambling experiments. The law of chemical equilibrium (the law of mass action of Guldberg and Waage) gives the equilibrium constant \(K_c\) as the ratio of product to reactant concentrations each raised to its stoichiometric coefficient. For gaseous reactions \(K_p\) is used, with \(K_p=K_c(RT)^{\Delta n}\); pure solids and liquids are omitted from heterogeneous equilibrium constants. The magnitude of \(K\) indicates the extent of a reaction, while the reaction quotient \(Q\) predicts the direction of net change. Equilibrium connects to thermodynamics through \(\Delta G^{\circ}=-RT\ln K\). Le Chatelier's principle explains how concentration, pressure, temperature and catalysts affect equilibrium, a catalyst speeding both directions equally without shifting the position. The unit then turns to ionic equilibrium: strong and weak electrolytes; the Arrhenius, Brønsted-Lowry (conjugate acid-base pairs) and Lewis concepts of acids and bases; ionisation of acids and bases; the ionic product of water \(K_w=1\times10^{-14}\), the pH scale, buffer solutions and solubility product.

Equilibrium in physical processes and Henry's lawDynamic chemical equilibriumLaw of mass action and equilibrium constantKp-Kc relationship and heterogeneous equilibriaReaction quotient and Gibbs energyLe Chatelier's principleAcid-base concepts and conjugate pairsIonic product of water and pH scaleBuffers and solubility product

Key terms

Dynamic equilibrium

A state in which the forward and reverse processes occur at equal rates, so concentrations remain constant though both processes continue.

Equilibrium constant

The constant ratio of product to reactant concentrations, each raised to its stoichiometric coefficient, at a given temperature.

Reaction quotient

The same expression as the equilibrium constant but evaluated for non-equilibrium concentrations; comparing it with \(K\) predicts the reaction direction.

Le Chatelier's principle

When a system at equilibrium is disturbed, it shifts so as to counteract the imposed change.

Conjugate acid-base pair

A Brønsted acid and base related by the gain or loss of a single proton.

Ionic product of water

The constant \(K_w=[H^+][OH^-]=1\times10^{-14}\) at 298 K for the self-ionisation of water.

Extra questions & answers

Try one from this chapter

At dynamic equilibrium, the rates of the forward and reverse reactions are:

Flashcards & interactive practice