Regent’s Warm-Up Which is an empirical formula?

Regent’s Warm-Up

• Which is an empirical formula?

• (1) P2O5 (3) C2H4

• (2) P4O6 (4) C3H6

Regent’s Warm-Up

• Which is an empirical formula?

• (1) P2O5 (3) C2H4

• (2) P4O6 (4) C3H6

Reaction Equilibrium

• AIM:

• How does a reaction at equilibrium change when it is disturbed?

• DO NOW:

• What is equal at equilibrium?

Reaction Equilibrium

• We can change the concentrations of reactants and products by disturbing or “stressing” a reaction

Reaction Equilibrium

• When disturbed the reaction will make adjustments to restore equilibrium

• The new equilibrium position is different, which means the amounts of reactants and products are changed

Henri Le Chatelier

• The chemist Henri Le Chatelier studied equilibrium conditions

• He developed rules for changing equilibrium based on his experiments

Le Chatelier’s Principle

• Any stress applied to a reaction in dynamic equilibrium causes the reaction to make a “shift” to relieve the stress

• A shift towards product formation is a shift to the right

• A shift towards reactant formation is a shift to the left

Stress 1: Concentration

• Changes in the amount or concentration of a product OR reactant will disturb (stress) an reaction at equilibrium

• The reaction adjusts to minimize any stresses

Stress 1: Concentration

• Given the reaction (see image) at equilibrium: What occurs when the concentration of H2(g) is increased?

• 1. The rate of the forward reaction increases and the concentration of N2(g) decreases.

• 3. The rate of the forward reaction and the concentration of N2(g) both increase.

• 2. The rate of the forward reaction decreases and the concentration of N2(g) increases.

• 4. The rate of the forward reaction and the concentration of N2(g) both decrease

Stress 2: Pressure/Volume

• If the volume of a reaction changes the equilibrium is disturbed

•  in volume causes an  in pressure

• The equilibrium will shift to relieve pressure if the pressure is  and  pressure if the pressure is 

Stress 2: Pressure/Volume

• Ammonia is produced commercially by the Haber reaction: . . . (see image)

• The formation of ammonia is favored by

• 1. an increase in pressure

• 3. removal of N2(g)

• 2. a decrease in pressure

• 4. removal of H2(g)

Stress 3: Temperature

• Changing temperature alters both the equilibrium position and the equilibrium constant

• Reactions are either endothermic or exothermic

Stress 3: Temperature

• What occurs when the temperature is increased in a system at equilibrium at constant pressure?

• 1. The rate of the forward reaction increases, and the rate of the reverse reaction decreases.

• 2. The rate of the endothermic reaction increases.

• 3. The rate of the forward reaction decreases, and the rate of the reverse reaction increases.

• 4. The rate of the exothermic reaction decreases.

Stress: Temperature

• Given the equilibrium reaction in a closed system as shown: What will be the result of an increase in temperature?

• 1. The equilibrium will shift to the left and [H2] will increase.

• 3. The equilibrium will shift to the right and [HI] will increase.

• 2. The equilibrium will shift to the left and [H2] will decrease.

• 4. The equilibrium will shift to the right and [HI] will decrease.

Le Chatelieres Principle

• Given the reaction at equilibrium: . . . (see image) Which change will cause the equilibrium to shift?

• 1. increase in pressure

• 3. addition of heat

• 2. increase in volume

• 4. addition of a catalyst

Le Chatelieres Principle

• Given the reaction at equilibrium (see image): The concentration of A(g) can be increased by

• 1. lowering the temperature

• 3. increasing the concentration of AB(g)

• 2. adding a catalyst

• 4. increasing the concentration of B(g)

Le Chatelieres Principle

• Given the reaction at equilibrium: . . . (see image) Which change will shift the equilibrium to the right?

• 1. increasing the temperature

• 3. decreasing the amount of SO2(g)

• 2. increasing the pressure

• 4. decreasing the amount of O2(g)