SC12 Flashcards
(13 cards)
What is a reversible reaction?
A reaction in which the products can easily be changed back to the reactants.
What is a forward reaction?
A reaction that describes reactants changing into products.
What is a backward reaction?
A reaction that describes products changing back into reactants.
What is dynamic equilibrium?
When a reaction is still occurring (dynamic) but the substances remain in balance (equilibrium).
Why does dynamic equilibrium only occur in closed systems?
In open systems, gases could escape so equilibrium would not be achieved.
What are the characteristics of dynamic equilibrium?
- Concentration/amounts of reactants and products remain constant (not necessarily equal)
- Rate of forward reaction = rate of backward reaction
What are the factors affecting the position/rate of equilibrium?
- Temperature
- Concentration
- Pressure - for gaseous reactions
- Catalyst - doesn’t affect the position of equilibrium, only affects the rate
How does temperature affect the position of equilibrium?
When temperature increases: equilibrium position shifts to the endothermic direction (transferring energy from the surroundings, cooling them down)
When temperature decreases: equilibrium position shifts to the exothermic direction (transferring energy to the surroundings, heating them up)
Check equilibria rules chem booklet p3 slide 23.
How does pressure affect the position of equilibrium and what type of reactions does it affect?
When gas pressure increases: equilibrium position shifts to the direction that forms fewer gas molecules (this reduces pressure)
When gas pressure decreases: equilibrium position shifts to the direction that forms more gas molecules (this increases pressure)
Pressure only affects the equilibrium position if the reaction involves different number of gas molecules on each side.
Check equilibria rules chem booklet p3 slide 23.
How does concentration affect the position of equilibrium?
When a concentration increases: equilibrium position shifts to the direction that uses up the substance that has been added
When a concentration decreases: equilibrium position shifts to the direction that forms more of the substance that has been removed
Check equilibria rules chem booklet p3 slide 23.
How does a catalyst affect the position/rate of equilibrium?
Adding a catalyst increases the rate of both the forward and the backward reaction to the same extent, thus there is no change on the position of the equilibrium. The equilibrium is only reached faster.
Check equilibria rules chem booklet p3 slide 23.
What is the Haber Process and its chemical equation?
It is where ammonia is produced by the reaction of nitrogen obtained from the air and hydrogen from natural gas (methane).
N₂ (g) + 3H₂ (g) endo <–> exo 2NH₃ (g)
What are the operating conditions of the Haber Process?
- Temperature of 450°C
- Pressure of 200 atmospheres
- Iron catalyst
- Ammonia is cooled, liquefied and constantly removed
- Unreacted hydrogen and nitrogen are constantly recycled back into the reaction vessel
Check diagram chem booklet p4 slide 25.
