Chemistry - 8 Rates and Equilibrium - 8.7 Energy and Reversible Reactions & 8.8 Dynamic Equilibrium & 8.9 Altering Conditions

If a reversible reaction transfers energy to its surroundings in the forward direction...

it will take in that amount of energy in the backwards direction

Copper (II) sulfate reversible reaction

hydrated copper (II) sulfate ⇌ anhydrous copper (II) sulfate + water

Copper (II) sulfate forward reaction [3]:

- endothermic
- blue crystals are heated
- crystals turn white

Copper (II) sulfate reverse reaction [3]:

- exothermic
- water is added to white crystals
- crystals steam and turn blue

Dynamic equilibrium

the rate of the forward reaction is equal to the rate of the reverse reaction

How equilibrium is reached [4]:

- initially only reactants are present in their highest concentration
- as they react, concentration decreases, so rate of forward reaction decreases
- as they react, concentration of products increases, so rate of reverse reaction increases
- eventually become equal

Le Châtelier's Principle

if stress is applied to a system at equilibrium, the position of equilibrium shifts to relieve the stress

Stresses to a system at equilibrium [3]:

- temperature
- pressure
- concentration

(LCP) If the pressure of a system at equilibrium rises...

the reaction will shift in the direction of the substance with fewer moles of gas

(LCP) If the temperature of a system at equilibrium rises...

the reaction will shift in the direction of the endothermic reaction

(LCP) If the concentration of one substance (e.g. reactant) in a system at equilibrium rises...

the reaction will shift to the side of the other substance (e.g. product)

(LCP) If the pressure of a system at equilibrium falls...

the reaction will shift in the direction of the substance with more moles of gas

(LCP) If the temperature of a system at equilibrium falls...

the reaction will shift in the direction of the exothermic reaction

(LCP) If the concentration of one substance (e.g. reactant) in a system at equilibrium falls...

the reaction will shift in the direction of that substance (e.g. reactant)