Lesson on Equilibrium

Chemical Equilibrium

Open Ended

What is chemical equilibrium in reactions?

Chemical Equilibrium

• Rate at which products are formed is the SAME rate at which reactants are formed

• Many reactions are reversible

• When a reaction has reached equilibrium we can't see any changes in the reactants concentration or in the products concentration

Chemical equilibrium is DYNAMIC because the reaction doesn't finish, the reactants continue to change into products and viceversa

https://www.youtube.com/watch?v=crr5ZMHCJ_Y

https://www.youtube.com/watch?v=n91fiyEmT-s

Le Chatelier's Principle

• If dynamic equilibrium is disturbed by changing the conditions, then the position of the equilbrium moves to counteract the change.

• Conditions that can be changed: TEMPERATURE, PRESSURE AND CONCENTRATION.

Multiple Choice

If we add CaCl₂ to the test tube, the equilibrium switches to the...?

• right (blue)

• left (pink)

• it reaches dynamic equilibrium (purple)

Multiple Select

If we add water (a product), the equilibrium switches to...?

• left (pink)

• right (blue)

• it reaches dynamic equilibrium (purple)

Temperature

• If a reaction is exothermic (releases heat), an increase in the temperature will force the equilibrium to the left, causing the system to absorb heat and thus partially ofsetting the rise in temperature.

• The opposite effect occurs for endothermic reactions, which are shifted to the right by rising temperature

Pressure

• The effect of pressure on equilibrium

  is significant only for reactions which involve different numbers of moles of gases on the two sides of the equation. 

• If the number of moles of gases increases, then an increase in the total pressure will tend to initiate a reverse reaction that consumes some the products, partially reducing the effect of the pressure increase.

Multiple Select

If we open a bottle of soda (decrease the pressure) we can see all the bubbles of gas forming and rising. This means the equilibrium shifted to the...?

• left (reactants)

• right (products)

• it doesn't shift