Equilibrium and le Chatelier's Principle

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Introduction for Year 12 Research Assignment

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Chemical Equilibrium:

Chemical Equilibrium Reversible Reactions Chapter 17

Equilibrium:

Equilibrium Equal? Stable? Balance? . =

Imagine – isolated zone – just Aus & NZ - No migration:

Imagine – isolated zone – just Aus & NZ - No migration

Population of Australia 20,600,900 Population of New Zealand 4,173,460:

Population of Australia 20,600,900 Population of New Zealand 4,173,460 Equilibrium Static

Population of Australia 20,600,900 Population of New Zealand 4,173,460:

Population of Australia 20,600,900 Population of New Zealand 4,173,460 Equilibrium Dynamic 20,000 pa 20,000 pa

Population of Australia 15,000,000 Population of New Zealand 3,000,000:

Population of Australia 15,000,000 Population of New Zealand 3,000,000 Equilibrium Not in 5,000 pa 20,000 pa

Population of Australia 18,000,000 Population of New Zealand 3,000,000:

Population of Australia 18,000,000 Population of New Zealand 3,000,000 Equilibrium Not in 20,000 pa 10,000 pa

Equilibrium populations remaining constant:

Equilibrium populations remaining constant Equilibrium Dynamic same same More important

Vapours above Liquids:

Vapours above Liquids CH 3 CH 2 OH (l)  CH 3 CH 2 OH (g) CH 3 CH 2 OH (l)

Rate Graph:

Rate Graph Time Rate Rate of evaporation Rate of condensation

Equilibrium Constant:

Equilibrium Constant N 2(g) + 3H 2(g)  2 NH 3(g) N 2(g) + H 2(g ) + H 2(g ) + H 2(g)  NH 3(g) + NH 3(g ) K = [NH 3 ] [NH 3 ] [N 2 ] [H 2 ] [H 2 ] [ H 2 ] K = [NH 3 ] 2 [N 2 ] [ H 2 ] 3

Equilibrium Constant:

Equilibrium Constant aA + bB + cC  zZ + yY + xX (a moles of A etc ) K = [Z] z [Y] y [X] x [A] a [B] b [C] c Size of K: High – little reactant remaining at equilibrium Low – little product formed at equilibrium Calculations p 566 - 570

Changing Equilibrium Constant:

Changing Equilibrium Constant Rigging it to get what we want

Equilibrium example:

Equilibrium example Equilibrium Dynamic

Le Chatelier’s Principle:

Le Chatelier’s Principle Any change that affects the position of an equilibrium, will cause the equilibrium to shift, if possible, in such as way as to oppose the effect of that change. Examples You make it hotter? Favours an endothermic reaction You increase the pressure? Favours the arrangement with less pressure. Opposite!

Temperature:

Temperature N 2(g) + 3H 2(g)  2 NH 3(g )  H = -46kJ kJ/ mol Exothermic – forward reaction make it hot Reduce temperature – favours this reaction Increase temperature – favours reverse reaction

Pressure:

Pressure Avogadro’s hypothesis: Equal volumes of gases (at the same pressure and temperature) contain the same number of molecules. Never mind the size of the molecules. n determines V

Pressure:

Pressure N 2(g) + 3H 2(g)  2 NH 3(g )  H = -46kJ kJ/ mol Volume of a gas depends on n n for left side? 4 n for right side? 2 Increase pressure– favours forward reaction Decrease pressure– favours reverse reaction

Concentration:

Concentration N 2(g) + 3H 2(g)  2 NH 3(g )  H = -46kJ kJ/ mol Pump in more N 2(g) Favours forward reaction Pump in more NH 3(g ) Favours reverse reaction Pump in more H 2(g ) Favours forward reaction

Dilemma – chemical manufacturing:

Dilemma – chemical manufacturing Manipulate factors to obtain the highest equilibrium constant Improve yield Problems? Expensive equipment C onflict with reaction rates