Homogenous & Heterogeneous Equilibria. Homogenous Equilibria equilibrium conditions for rxns in which all the reactants & products are in the same state eg. 2CO (g) + O 2(g) 2CO 2(g) Heterogenous Equilibria
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equilibrium conditions for rxns in which all the reactants & products are in the same state
eg. 2CO(g) + O2(g) 2CO2(g)
equilibrium conditions for rxns that involve substances in more than 1 state
eg. NH4Cl(s) NH3(g) + HCl(g)
 of solids & liquids in a chem. rxn. do not change substantially and so are not included in the equilibrium constant
[solid & liquid] change during a rxn, left out of Keq
eg. C(s) + H2O(g) CO(g) + H2(g)
Keq = [CO][H2] .
It is hard to tell if a rxn. has reached equilibrium
The “reaction quotient” (Q) is used to determine if a rxn. is @ equilibrium
Q is calculated like Keq except the ’s are taken @ the time of measurement, not necessarily @ equilibrium
Thus we can compare the value of Q to the value of Keq to see how the rxn. is progressing
Rxn. is @ equilibrium when Keq = Q
At 473°C, nitrogen gas is reacted with hydrogen gas to produce ammonia. A measurement was taken as the reaction proceeded and it was found that there was 0.15 M of nitrogen gas, 0.0020 M of hydrogen gas, and 0.15 M of ammonia. Given that the Keq is 0.105, is the reaction at equilibrium?
temp. = 473°C [NH3] = 0.15 M
Keq = 0.105 [N2] = 0.15 M
[H2] = 0.0020 M
Keq = [NH3]2Q = (0.15)2 .
= 1.9 x 107
Keq Q this rxn. is NOT @ equilibrium
Q < Keq
Q is less thanKeq
denominator is too large and numerator is too small
too much of reactants, too little of products
rxn. will proceed to the right (in the direction of products)
Q is greater thanKeq
denominator is too small and numerator is too large
too much products, too little reactants
rxn. will proceed to the left (in the direction of reactants)
COCl2(g) CO(g) + Cl2(g)Keq = 170
At the time of measurement:
[CO] = 0.15 M
[Cl2] = 0.15 M
[COCl2] = 1.1 x 103 M
Is the rxn. @ equilibrium? If not, which direction will it proceed?
[COCl2] (1.1 x 103)
Q < Keq thus rxn. is NOT @ equilibrium
there is too much reactants
rxn. will shift right in the direction of products