Last time we had as an example the hydrogenation of
unsaturated organic molecules.
Cornered by Mike Baldwin
A sample exam is posted online. Give it a try under
simulated conditions: 45 min, closed book, etc.
Solutions are now posted online. 1 2
Unit 2 – Chemical Equilibrium and applications Chapter 17 – Chemical Equilibrium
Principles of chemical equilibrium Chapter 17 Qualitative
What is chemical equilibrium
Acid–baEsquilibria Chapt1 8r,
91 r e t pyathi l i bul oS Equilibrium constant
Compleixns Chapt1er Direction of the reaction
Le Chatelier’s principle
Determination of K
Calculation of equilibrium positions
Volume and temperature effects
Chemical equilibrium N 2 –4NO eq2ilibrium system
All chemical reactions reach a state of equilibrium. NO dark brown gas poisonous, corrosive
That is, they reached a state in which reactants are left,
N 2 4 colorless gas
products are present but nothing seems to be happening.
In a sealed flask at room temperature both exist
Wrong !!! together.
N 2O 4 (g) 2 NO 2 (g)
Reaction is continuing on the microscopic level, but the
rate at which the products are formed, equals exactly to The amounts of each gas in the flask are dictated by the
the rate at which reactants are formed, so there is No equilibrium constant.
NET change. Figure 17.1
stoich coefficients stoich coefficients
k1[reactants] = k –1[products]
(products = reactant of the reverse reaction)
K = equil. constant =k –1= [reactants]stoich coefficients
Note: Equi. Constant is capital K, rate const. is small k. 5 6
Figure 17.3 When the concentrations are constant, the rxn is at
3 different terms we’ll encounter:
The position of equilibrium is defined by the
collection of concentrations of the reactants and
products at equilibrium.
The direction of reaction
The equilibrium consta.Kt
K is constant if the temperature is constant.
The equilibrium constant In terms of partial pressures
P P m
jA (g) kB (g) C (g) mD