approaching equilibrium lesson 1
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Approaching Equilibrium Lesson 1. Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products. Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products - PowerPoint PPT PresentationTRANSCRIPT
ApproachingEquilibrium
Lesson 1
Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products
Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ ProductsAlways on left Always on right
Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products
Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products
Forward Rate is fromleft to right
Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products
Reverse Rate is from right to left
Lets see what happens to some reactants if they are placed in a reaction vessel and allowed to react.
Reactants Products
Approaching Equilibrium
Forward Rate
Reverse Rate
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Are Equal
Reactants Products
Approaching Equilibrium
Reverse Rate
Forward Rate
Are Equal
Are Constant
Reactants Products
Reverse Rate
Forward Rate
Are Equal
Are ConstantSame as before
Approaching Equilibriumfrom Products
Time [Reactant] Forward Rate [Product] Reverse Rate Net Rate 0 8000 170 0 0 170 5 7500 160 1000 16 144 10 6800 145 2000 20 125 15 5600 120 2500 30 90 20 4600 100 3200 40 60 25 3600 84 4000 50 34
30 2900 75 4900 56 19
35 2000 65 6000 58 7
40 1600 60 6000 60 0
45 1600 60 6000 60 0
50 1600 60 6000 60 0
Equilibrium has been attained after 40 minutes. The forward and reverse rates are equal and the reactant and product concentrations are constant.
Graph the [reactant] and [product] as equilibrium is approached.
Concentration 8000
7000 6000
5000
4000
3000
2000
1000
0 15 30 Time
equilibrium
Graph the forward, reverse, & net rates as equilibrium is approached.
Rate 160
140 120
100
80
60
40
20
0 15 30 Time
equilibrium
Approaching Equilibrium
Reactant concentrations start high and decrease as the reaction proceeds. The forward rate, which depends on collisions of the reactants, also decreases. Product concentrations start at zero and increase as the reaction proceeds. The reverse rate, which depends on collisions of the products, also increases. Eventually the forward rate is equal to the reverse rate and the concentrations are constant. This is equilibrium.
Characteristics of a System at Equilibrium The Forward rate = The Reverse rate The Reactant and Product concentrations are constant The Macroscopic (observable) properties are constant The system is Dynamic as the forward and reverse reactions continue. The equilibrium can be approached from starting with reactants or starting with products.
Reactants Products
Approaching Equilibriumfrom Products
Reverse Rate
Forward Rate
Reactants Products
Reverse Rate
Forward Rate
Approaching Equilibriumfrom Products
Reactants Products
Reverse Rate
Forward Rate
Approaching Equilibriumfrom Products
Reactants Products
Reverse Rate
Forward Rate
Approaching Equilibriumfrom Products
Reactants Products
Reverse Rate
Forward Rate
Approaching Equilibriumfrom Products
Reactants Products
Reverse Rate
Forward Rate
Are Equal
Are ConstantSame as before
Approaching Equilibriumfrom Products
If you start with products all aspects of the approach to equilibrium are reversed!
Products and Reverse Rate decrease
Reactants and Forward Rate increases
Conditions Necessary for Equilibrium The system is closed. The temperature is constant. The Ea is low enough so that the reaction is reversible.
Simulation1