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Approaching Equilibrium Lesson 1. Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products.

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Presentation on theme: "Approaching Equilibrium Lesson 1. Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products."— Presentation transcript:

1 Approaching Equilibrium Lesson 1

2 Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products

3 Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products Always on leftAlways on right

4 Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products

5 Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products Forward Rate is from left to right

6 Approaching Equilibrium Many chemical reactions are reversible if the activation energy is low. Reactants ⇌ Products Reverse Rate is from right to left

7 Lets see what happens to some reactants if they are placed in a reaction vessel and allowed to react.

8 Reactants Products Approaching Equilibrium Forward Rate Reverse Rate

9 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate

10 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate

11 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate

12 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate

13 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate

14 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate

15 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate Are Equal

16 Reactants Products Approaching Equilibrium Reverse Rate Forward Rate Are Equal Are Constant

17 Reactants Products Reverse Rate Forward Rate Are Equal Are Constant Same as before Approaching Equilibrium from Products

18 Time[Reactant] Forward Rate[Product] Reverse Rate Net Rate

19 Equilibrium has been attained after 40 minutes. The forward and reverse rates are equal and the reactant and product concentrations are constant.

20 Graph the [reactant] and [product] as equilibrium is approached. Concentration Time equilibrium

21 Graph the forward, reverse, & net rates as equilibrium is approached. Rate Time equilibrium

22 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.

23 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.

24 Reactants Products Approaching Equilibrium from Products Reverse Rate Forward Rate

25 Reactants Products Reverse Rate Forward Rate Approaching Equilibrium from Products

26 Reactants Products Reverse Rate Forward Rate Approaching Equilibrium from Products

27 Reactants Products Reverse Rate Forward Rate Approaching Equilibrium from Products

28 Reactants Products Reverse Rate Forward Rate Approaching Equilibrium from Products

29 Reactants Products Reverse Rate Forward Rate Are Equal Are Constant Same as before Approaching Equilibrium from Products

30 If you start with products all aspects of the approach to equilibrium are reversed! Products and Reverse Rate decrease Reactants and Forward Rate increases

31 Conditions Necessary for Equilibrium The system is closed. The temperature is constant. The Ea is low enough so that the reaction is reversible. Simulation1


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