This document discusses chemical equilibrium. It defines chemical equilibrium as a state where the rates of the forward and reverse reactions are equal, such that the concentrations of reactants and products no longer change over time. It describes how equilibrium can be altered according to Le Chatelier's principle - if a stress such as a change in concentration, temperature, or pressure is applied to a system at equilibrium, the position of equilibrium will shift to counteract the applied change and re-establish equilibrium. Specific examples are provided of how changing concentration, temperature, and pressure can shift equilibrium in reversible reactions.
7. Effect of Change in Concentration on Equilibrium
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+ ve
8. Effect of Change in concentration and temperature
on Equilibrium constant
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Add water
Add conc. HCl
Add CaCl2
Hot water
bathCold
water
bath
9. Effect of Change in Pressure on Equilibrium
• Adding CaCl2 or NaCl or conc. HCl results in concentration of reactant (Cl-
)
to increase, (Qc < Kc), the reactions shifts to the right to consume increased
amount of Cl-
, more [CoCl4]2-
(aq) (blue) is produced.
• Adding water, (Qc > Kc), the reactions shifts to the left as more water is
consumed in making [Co(H2O)6]2+
• Placing [Co(H2O)6]2+
in boiling water, reaction shifts towards forward
direction as this reaction is endothermic.
• Placing [CoCl4]2-
(aq) (blue) in ice bath shifts reaction towards to backward
direction.
• Adding or releasing pressure on gaseous reactions also has the same effect
as concentration.
Adding Catalyst has no effect on equilibrium.
10. Learning Check
Write the equilibrium constant expression for each reaction.
•2SO2(g)+O2(g) 2SO⇌ 3(g)
•N2O(g)+1/2O2(g) 2NO(g)⇌
•Cu(s)+2Ag+
(aq) Cu⇌ +2
(aq)+2Ag(s)
•CaCO3(g) CaCO(s)+CO⇌ 2(g)
•2NaHCO3(s) Na⇌ 2CO3(s)+CO2(g)+H2O(g)
•H+(aq)+OH–(aq)→H2O(l)
•Write the Partial Pressure Equilibrium: C(s)+O2(g)→CO2(g)
•What is the Kc of the following reaction?
2SO2(g)+O2(g) 2SO⇌ 3(g)
SO2(g)=0.2M, O2(g)=0.5M, SO3(g)=0.7M
Also, What is the Kp of this reaction? At room temperature?
The lower case letters represent the number of moles of each molecule, the upper case letters represent the molecule itself, and the letters in the parenthesis always represents the state of matter of the molecule.
The equilibrium constant of concentration gives the ratio of concentrations of products over reactants for a reaction that is at equilibrium
The lower case letters represent the number of moles of each molecule, the upper case letters represent the molecule itself, and the letters in the parenthesis always represents the state of matter of the molecule.
The equilibrium constant of concentration gives the ratio of concentrations of products over reactants for a reaction that is at equilibrium
It is usually supplied as the hexahydrate CoCl2. 6H2O, which is one of the most commonly used cobalt compounds in the lab. Because of the ease of the hydration/dehydration reaction, and the resulting color change, cobalt chloride is used as an indicator for water in desiccants
Since the two forms are in equilibrium by adjusting the chloride concentration about equal amounts of the pink and blue complexes can be obtained.