Presentation is loading. Please wait.

Presentation is loading. Please wait.

The Equilibrium Law. Write equilibrium law expressions from balanced chemical equations for heterogeneous and homogeneous systems. Use the value of the.

Similar presentations


Presentation on theme: "The Equilibrium Law. Write equilibrium law expressions from balanced chemical equations for heterogeneous and homogeneous systems. Use the value of the."— Presentation transcript:

1 The Equilibrium Law

2 Write equilibrium law expressions from balanced chemical equations for heterogeneous and homogeneous systems. Use the value of the equilibrium constant to explain how far a system at equilibrium has gone towards completion. Additional KEY Terms

3 Law of mass action (equilibrium law): A ratio to show the relationship between [reactants] and [products] at equilibrium. The value of this ratio is called the equilibrium constant. aA + bB cC + dD

4 k f [A] a [B] b = k r [C] c [D] d At equilibrium rates are equal: rate forward = k f [A] a [B] b rate reverse = k r [C] c [D] d If the forward and reverse reactions were elementary reactions, the rate laws would be: aA + bB cC + dD

5 The ratio of rate constants was condensed to one constant, K c, called the equilibrium constant. The law of mass action or equilibrium law then becomes = kfkf krkr [A] a [B] b [C] c [D] d = KcKc [A] a [B] b [C] c [D] d = KcKc Reactants Products

6 Homogeneous equilibria: Reactants and products are all in either gas (g) or aqueous (aq) phase. N 2 (g) + 3 H 2 (g) 2 NH 3 (g) Writing the Equilibrium Law = KcKc [N 2 ][H 2 ] 3 [NH 3 ] 2

7 Heterogeneous equilibria - reactants and products in more than one state. When writing the mass action expression, omit solids (s) or liquids (l). Concentration of solids and liquids don't change at constant temperatures. C (s) + H 2 O (g) CO (g) + H 2(g) = KcKc [CO][H 2 ] [H 2 O]

8 The Equilibrium Constant

9 As with most constants, the only factor affecting K c is temperature. The K c can indicate whether there are more products or reactants at equilibrium: = KcKc [A] a [B] b [C] c [D] d = KpKp P A a P B b P C c P D d

10 Rate Concentration Case 1: If K c = 1 [products] = [reactants] aA + bB cC + dD tete tete

11 Concentration Rate Case 2: If K c > 1 [product] > [reactant] Products are favoured. aA + bB cC + dD tete tete

12 Concentration Rate Case 3: If K c < 1 [product] < [reactant] Reactants are favoured. aA + bB cC + dD tete tete

13 Most chemical reactions are reversible. Chemical equilibrium can only occur in a closed system. Equilibrium is when rates are equal AND the [ ]s remains constant. K c can be used to determine the equilibrium position.

14 CAN YOU / HAVE YOU? Write equilibrium law expressions from balanced chemical equations for heterogeneous and homogeneous systems. Use the value of the equilibrium constant to explain how far a system at equilibrium has gone towards completion. Additional KEY Terms


Download ppt "The Equilibrium Law. Write equilibrium law expressions from balanced chemical equations for heterogeneous and homogeneous systems. Use the value of the."

Similar presentations


Ads by Google