Presentation is loading. Please wait.

Presentation is loading. Please wait.

Chemical equilibrium is a state in which the forward and reverse reactions balance each other because they take place at equal rates. Rateforward reaction.

Similar presentations


Presentation on theme: "Chemical equilibrium is a state in which the forward and reverse reactions balance each other because they take place at equal rates. Rateforward reaction."— Presentation transcript:

1

2 Chemical equilibrium is a state in which the forward and reverse reactions balance each other because they take place at equal rates. Rateforward reaction = Ratereverse reaction

3 Reversible reactions Chemical Equilibrium: Basic Concepts You can recognize that the ammonia-forming reaction reaches a state of chemical equilibrium because its chemical equation is written with a double arrow like this. Topic 22 Topic 22 At equilibrium, the concentrations of reactants and products are constant. However, that does not mean that the amounts or concentrations of reactants and products are equal.

4 Factors Affecting Chemical Equilibrium Chemical Equilibrium: Basic Concepts Topic 22 Topic 22 Le Châtelier’s principle states that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress. If an additional amount of reactant (NO or Br 2 ) is added to the system, the equilibrium will shift to the right, that is, more product (NOBr) will be formed. For example, consider the equilibrium system

5 Factors Affecting Chemical Equilibrium Chemical Equilibrium: Basic Concepts Topic 22 Topic 22 Conversely, adding more NOBr to the system will result in a shift to the left, forming more NO and Br 2. The removal of a reactant or product also results in a shift in the equilibrium. Removing a reactant causes the equilibrium to shift to the left, forming more reactants. Removing the product causes a shift to the right, forming more product.

6 Changes in volume Chemical Equilibrium: Basic Concepts Topic 22 Topic 22 Le Châtelier’s principle also applies to changes in the volume of the reaction vessel containing the equilibrium system. The equilibrium will shift to relieve the stress of increased pressure. Suppose the volume of the reaction vessel for the system is decreased, resulting in an increase in pressure.

7 Changes in volume Chemical Equilibrium: Basic Concepts Topic 22 Topic 22 In this case, the shift will be to the right because three moles of reactant gas combine to form only two moles of product gas. Thus, a shift toward the product will reduce the pressure of the system. If the volume of the reaction vessel was increased, the equilibrium would shift to the left, and more of the reactants would be formed.

8 Changes in volume Chemical Equilibrium: Basic Concepts Topic 22 Topic 22 Note that changing the volume of the reaction vessel causes no shift in the equilibrium when the number of moles of product gas equals the number of moles of reactant gas; an example is the equilibrium

9 Changes in temperature Chemical Equilibrium: Basic Concepts Topic 22 Topic 22 Consider the thermochemical equation for the reversible formation of hydrogen chloride gas from its elements. The forward reaction releases heat, so you can consider heat as a product in the forward reaction and a reactant in the reverse reaction.

10 Changes in temperature Chemical Equilibrium: Basic Concepts Topic 22 Topic 22 Raising the temperature of this system requires the addition of heat, which shifts the equilibrium to the left and reduces the concentration of hydrogen chloride. Lowering the temperature of the system means that heat is removed, so the equilibrium relieves the stress by shifting to the right, increasing both the concentration of hydrogen chloride.


Download ppt "Chemical equilibrium is a state in which the forward and reverse reactions balance each other because they take place at equal rates. Rateforward reaction."

Similar presentations


Ads by Google