SCH 4U1
EQUILIBRIUM
EQUILIBRIUM DEALS WITH THE QUESTION: WILL A
REACTION GO TO COMPLETION?
SOME REACTIONS WILL GO TO COMPLETION. H2(g) + O2(g) ---> H2O(g)
THERE ARE MANY REACTIONS THAT DO NOT GO TO
COMPLETION. THE PRODUCTS REFORM THE REACTANTS. THIS IS
INDICATED BY A DOUBLE ARROW.
H2CO3(aq) ↔ H2O(l) + CO2(g)
THIS INDICATES THE REACTION IS PROCEEDING IN BOTH
DIRECTIONS SIMULTANEOUSLY. SINCE THE REACTION
CONTINUES THIS IS CALLED A DYNAMIC EQUILIBRIUM. AN
EQUILIBRIUM CONSTANT CAN BE EXPRESSED FOR EACH
REACTION. THIS NUMBER SHOWS THE EXTENT OF THE
EQUILIBRIUM (LEFT OR RIGHT).
CONSIDER THE GENERIC REACTION, THE EQUILIBRIUM
CONSTANT CAN BE FOUND BY:
aA + bB ↔ cC + dD
K = [C]c[D]d
[A]a[B]b
FOR EXAMPLE, THE REACTION: H2(g) + I2(g) <-> 2 HI(g)
HAVE EQUILIBRIUM CONCENTRATIONS OF:
H2 = 4.8 x 10-4 mol/L; I2 = 4.8 x 10-4 mol/L; HI = 3.5 x 10-3 mol/L
K=
[HI]2
[H2][I2]
K = ____
*THIS VALUE IS SPECIFIC FOR THE TEMPERATURE 698 K.
ex. GIVE THE EXPRESSION FOR THE EQUILIBRIUM CONSTANT.
a) 2 SO2(g) + O2(g) <-> 2 SO3(g)
b) CH4(g) + H2O(g) <-> CO(g) + 3 H2(g)
c) CaCO3(s) <-> CaO(s) + CO2(g)