2. Regent ’ s Warm-Up A substance is classified as an electrolyte because (1) it has a high melting point (2) it contains covalent bonds (3) its aqueous solution conducts an electric current (4) its aqueous solution has a pH value of 7.

3. Regent ’ s Warm-Up A substance is classified as an electrolyte because (1) it has a high melting point (2) it contains covalent bonds (3) its aqueous solution conducts an electric current (4) its aqueous solution has a pH value of 7.

4. Reaction Equilibrium Aim : What Is Reaction Equilibrium? Do Now : What Controls Equilibrium in the Body? How?

5. Reaction Equilibrium Equilibrium in Chemistry refers to a balance between products and reactants MOST chemical reactions are reversible, which means can go in the forward direction and form products or in the reverse direction and form reactants.

6. Reaction Equilibrium Once a rxn starts the fwd rxn over time will slow down or the rate of the fwd reaction decreases In the example, the concentration of reactants A and B will decrease as the reaction goes in the fwd direction, while the products C and D increases

7. Reaction Equilibrium As the rate of the fwd reaction decreases the rate of the rev reaction begins to increase After time the rates of the fwd and rev rxns will become equal CHANGE When the rates are equal the concentrations of reactants and products will no longer CHANGE THIS IS CALLED A DYNAMIC EQUILIBRIUM

8. Reaction Equilibrium The concentrations of reactants and products are NOT equal in a dynamic equilibrium If at equilibrium the PRODUCTS are greater the FORWARD reaction is favored That means in our example the concentrations of C and D will be greater than A and B

9. Reaction Equilibrium If at equilibrium the REACTANTS are greater the REVERSE reaction is favored That means in our example at equilibrium the concentrations of A and B will be greater than C and D

10. Reaction Equilibrium Therefore Dynamic Equilibrium occurs when opposing rates are equal (rate of fwd reaction = rate of rev reaction) The Law of Mass Action expresses the position of equilibrium numerically

11. Reaction Equilibrium Therefore Dynamic Equilibrium occurs when opposing rates are equal (rate of fwd reaction = rate of rev reaction) The Law of Mass Action expresses the position of equilibrium numerically

12. Reaction Equilibrium Let ’ s try some equilibrium basics Which statement correctly describes a chemical reaction at equilibrium? 1. The concentrations of the products and reactants are equal. 3. The rate of the forward reaction is less than the rate of the reverse reaction. 2. The concentrations of the products and reactants are constant. 4. The rate of the forward reaction is greater than the rate of the reverse reaction. Which statement correctly describes a chemical reaction at equilibrium? 1. The concentrations of the products and reactants are equal. 2. The rate of the forward reaction is less than the rate of the reverse reaction. 3. The concentrations of the products and reactants are constant. 4. The rate of the forward reaction is greater than the rate of the reverse reaction.

13. Reaction Equilibrium Let ’ s try some equilibrium basics Which statement correctly describes a chemical reaction at equilibrium? 1. The concentrations of the products and reactants are equal. 2. The rate of the forward reaction is less than the rate of the reverse reaction. 3. The concentrations of the products and reactants are constant. 4. The rate of the forward reaction is greater than the rate of the reverse reaction.

14. Reaction Equilibrium For a chemical reaction is at equilibrium. Compared to the rate of the forward reaction, the rate of the reverse reaction is: 1. faster and more reactant is produced 2. the same and the reaction has stopped 3. faster and more product is produced 4. the same and the reaction continues in both directions

15. Reaction Equilibrium For a chemical reaction is at equilibrium. Compared to the rate of the forward reaction, the rate of the reverse reaction is: 1. faster and more reactant is produced 2. the same and the reaction has stopped 3. faster and more product is produced 4. the same and the reaction continues in both directions

16. Reaction Equilibrium Given the equilibrium reaction at STP:... Which statement correctly describes this system? 1. The forward and reverse reaction rates are equal. 2. The concentrations of N 2 O 4 and NO 2 are equal. 3. The forward and reverse reaction rates are both increasing. 4. The concentrations of N 2 O 4 and NO 2 are both increasing.

17. Reaction Equilibrium Given the equilibrium reaction at STP:... Which statement correctly describes this system? 1. The forward and reverse reaction rates are equal. 2. The concentrations of N 2 O 4 and NO 2 are equal. 3. The forward and reverse reaction rates are both increasing. 4. The concentrations of N 2 O 4 and NO 2 are both increasing.

18. Reaction Equilibrium Which factors must be equal in a reversible chemical reaction at equilibrium? 1. the activation energies of the forward and reverse reactions 2. the concentrations of the reactants and products 3. the rates of the forward and reverse reactions 4. the potential energies of the reactants and products

19. Reaction Equilibrium Which factors must be equal in a reversible chemical reaction at equilibrium? 1. the activation energies of the forward and reverse reactions 2. the concentrations of the reactants and products 3. the rates of the forward and reverse reactions 4. the potential energies of the reactants and products