Equilibrium
Class 11 · Chemistry
4 ideas in Class 11 Chemistry, explained in plain words, with games and quizzes to practise.
Dynamic Equilibrium and Mass Action
Part of: Balance and Shifts
Equilibrium never sleeps: forward and reverse runs match, holding concentrations steady. Mass action prices each state as products over reactants to powers. Huge constants mean product oceans; tiny ones mean reactant lakes.
Why it matters. Still levels hide busy traffic. The ratio predicts every mixture's fate.
Formulas
- Kc = products over reactants to powers.
- Doubling the equation squares K.
Key words
- Dynamic equilibrium
- : Equal opposing rates holding concentrations steady.
- Law of mass action
- : Each state priced as products over reactants to powers.
- Equilibrium constant
- : Huge means product oceans; tiny means reactant lakes.
- Catalyst rule
- : Speeds both directions equally, keeping K fixed.
Try it in two minutes
- Cover water and watch the level hold.
- Match two escalators head to head.
- Price a mixture by its ratio.
Try at home. Balance inflow and outflow in a sink.
Equilibrium Constants and Le Chatelier
Part of: Balance and Shifts
Pressure constants trade with concentration ones by RT powers of mole change. The reaction quotient points the way: above K it retreats, below it advances. Systems fight changes: cooling feeds heat-makers, pressure feeds the fewer-mole side, and temperature alone moves K.
Why it matters. Factories steer yield with these levers. Reading Q against K predicts every nudge.
Formulas
- Kp = Kc (R T)^(mole change)
- Q above K retreats; Q below K advances.
Key words
- Kp
- : Pressure constant, trading with Kc by RT powers of mole change.
- Reaction quotient
- : Above K it retreats; below it advances.
- Le Chatelier's principle
- : Systems fight changes in heat, pressure and concentration.
- Inert gas rule
- : No shift at fixed volume.
Try it in two minutes
- Compare Q with K for a mixture.
- Chill an exothermic mix and watch.
- Squeeze a gassy equilibrium.
Try at home. Shift tea colour with hot and cold water.
Acids, Bases and pH
Part of: Ions in Water
pH is the negative log of hydrogen ion concentration; water splits to one part in ten to the fourteen. Strong acids split fully, weak ones barely, priced by Ka. Conjugate pairs differ by one proton, and bases mirror the same rules through Kb and pOH.
Why it matters. Soils, rivers, food and rain all quote pH. Logs turn vast ranges into handy numbers.
Formulas
- pH = - log[H+]; pOH = - log[OH-]
- pH + pOH = 14 (at 298 K)
- Kw = [H+][OH-] = 1.0 x 10^-14
Key words
- pH
- : The negative log of hydrogen ion concentration.
- Strong acid
- : Splits fully in water.
- Weak acid
- : Splits barely, priced by Ka.
- Conjugate pair
- : Acid-base pairs differing by one proton.
- Ionic product of water
- : Kw = 1.0 times 10 to the power minus 14.
Try it in two minutes
- Test vinegar, soap and water with strips.
- Compute pH from a concentration.
- Compare strong and weak bottles.
Try at home. Rank kitchen liquids by pH strips.
Salts, Buffers and Solubility
Part of: Ions in Water
Weak ions hydrolyse, tilting water acidic or basic. Buffers pair weak with conjugate to soak additions. Insoluble salts price dissolving by Ksp with powers per ion; shared ions push solids back out, letting analysis separate metals group by group.
Why it matters. Lakes, soap, caves and labs all balance these. Ksp tables predict every precipitate.
Formulas
- AgCl type: s = root(Ksp)
- AX2 type: Ksp = 4 s^3
Key words
- Hydrolysis
- : Weak ions tilting water acidic or basic.
- Buffer
- : Weak plus conjugate soaking small additions.
- Solubility product
- : Dissolving priced by Ksp with powers per ion.
- Common ion effect
- : Shared ions pushing solids back out.
Try it in two minutes
- Test salt solutions with strips.
- Add drops to a buffer versus water.
- Mix lead with chloride and watch.
Try at home. Test baking soda versus vinegar buffers.
What your child will practise
- Acids, Bases and pH: Jungle Puzzle (Clue Puzzle)
- Acids, Bases and pH: Jungle Quick Fire (Quick Fire)
- Dynamic Equilibrium and Mass Action: Candy Puzzle (Clue Puzzle)
- Equilibrium Constants and Le Chatelier: Candy Quest (Flip and Match)
- Salts, Buffers and Solubility: Space Quick Fire (Quick Fire)
- Quiz: Acids, Bases and pH (8 questions)
- Quiz: Dynamic Equilibrium and Mass Action (8 questions)
- Quiz: Equilibrium Constants and Le Chatelier (8 questions)
- Quiz: Salts, Buffers and Solubility (8 questions)