Equilibrium Definition Class Demo with hall • Chemical Equilibrium – when the rate of the forward and reverse reactions are equal • Dynamic – Reactions at eq never stop • Equilibrium DOES NOT mean that the amount of reactants and products are equal. They have reached an unchanging ratio

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Definition Equilibrium GI

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Definition 

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N2O4(g) 2NO2(g) Clear Brown Cold Hot 1. Starting with all reactants (N2O4) N2O4(g) 2NO2(g)

Graphs

2. Starting with all products (NO2)

Eq. Constants 1. Kc = Eq. Constant involving molarity a. Molarity = [ ] b. Example = [0.50 M] 2. Kp = Eq. Constant involving pressure a. Atmospheres b. We live at about 1 atm 3. Generic Example aA + bB cC + dD

Heterogeneous Equilibrium 1. More than one state is present 2. Exclude solids and liquids from K. (not considered to have a molarity or pressure)

Eq. Constants 2O3(g)

3O2(g)

2NO(g) + Cl2(g) H2(g) + I2(g)

2NOCl(g) 2HI(g)

Heterogeneous Eq. SnO2(s) + 2CO(g)

Sn(s) + 2CO2(g)

Pb(NO3)2(aq)+Na2SO4(aq) PbSO4(s) +2NaNO3(aq)

Ba2+(aq) + SO42-(aq)

BaSO4(s)

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A Note About Water 1. Exclude liquid water (often the solvent) 2. Keep gaseous water 3. Examples CO2(g) + H2(g) 3Fe(s) + 4H2O(g)

CO(g) + H2O(l) Fe3O4(s) + 4H2(g)

1. Does the following reaction favor the products or reactants? N2(g) + O2(g) 2NO(g) Kc = 1 X 10-30 2. For the following reaction, Kc = 794 at 298 K and Kc = 54 at 700 K. Should you heat or cool the mixture to promote the formation of HI? H2(g) + I2(g) 2HI(g)

1. Kc= 2.5 X 10-30 for N2(g) + O2(g) 2NO(g) calculate Kc for: 2NO(g) N2(g) + O2(g) 2. Calculate Kc for ½ N2(g) + ½ O2(g)

NO(g)

3. The Kc for N2(g) + 3H2(g) 2NH3(g) is 4.43 X10-3. Calculate Kc for: 2N2(g) + 6H2(g) 4NH3(g)

Calculate Kp for the following reaction at 300 oC:

Converting Between Kc and Kp Kp = Kc (RT)

1. An example CO(g) + Cl2(g) COCl2(g) Kc = 4.6 X 109 2. Rules K>>1 Favors the products K