C8: Rates and Equilibrium

Question 1

Name the things that affect the rate of a reaction

Answer 1

Concentration
Pressure
Volume
Temperature
SA:V
Catalyst

Question 2

What is collision theory?

Answer 2

Chemical reactions can only take place when the reacting particles collide with each other and the collisions have sufficient energy and frequency

Question 3

What determines the rate of a reaction?

Answer 3

The frequency of successful collisions
Number of successful collisions per second

Question 4

Why do some reactions tend to slow down?

Answer 4

There is initially a large number of reactant molecules, increasing the frequency of successful collisions, but over time, they begin to run out and the frequency of successful collisions is lesser

Question 5

How does concentration affect rate of reaction?
(solutions only)

Answer 5

Higher conc. = Faster rate
The more particles in a fixed volume, the higher the frequency of successful collisions, and thus, the faster the reaction
(Applies to solutions)

Question 6

How does surface area affect the rate of a reaction?
(solids only)

Answer 6

Higher surface area = faster reaction
The particles in fluids only react with the surface of solids
If a solid is broken up, it has more particles on its surface, thus increasing the frequency of collisions

Question 7

How does pressure affect the rate of a reaction?
(gasses only)

Answer 7

dunno lol

Question 8

How does temperature affect the rate of a reaction?

Answer 8

Higher temperature = faster reaction
Increasing the temp. increases the energy of the particles, therefore they collide faster and with more energy

Question 9

How do catalysts affect the rate of a reaction?

Answer 9

Catalysts increase the rate of chemical reactions, but are not used up by the reaction.
They do this by providing a different pathway for the reaction, that has a lower activation energy,
thus, it take less energy to cross the energy barrier, meaning more particles can successfully collide per second.

Question 10

What is are some benefits of using catalysts?

Answer 10

They allow reactions to take place quickly without increasing the temperature, which saves money.
They are not used up, meaning they can be reused.

Question 11

What are the energy changes in reversible reactions?

Answer 11

If it is endothermic in one direction, it is exothermic in the opposite direction

Question 12

What is dynamic equilibrium?

Answer 12

When the rate of the forward reaction is equal to the rate of the backward reaction
the same amount of energy is transferred in each case

Question 13

Describe the reversible reaction involving copper sulfate and water

Answer 13

endothermic
Hydrate copper sulfate (blue) <=> anhydrous copper sulfate (white) + water exothermic

Question 14

What happens when a system is in equilibrium, and a change is made to the conditions (Le Chatelier’s principle)?

Answer 14

The system reacts to counteract the change as the system is no longer in equilibrium

Question 15

What happens when concentration of a reactant/product is increased in a reversible reaction in a system in equilibrium?

Answer 15

More of the other reactant/product (reversible) will be made to counteract it, and bring the system back into equilibrium.

Question 16

What happens when you change the temperature in a reversible reaction in a system in equilibrium?

Answer 16

If it’s increased, the endothermic reaction will be favoured - energy is taken in to reduce outside temp..
If it’s decreased, the exothermic reaction is favoured, increasing the temperature of the surroundings to counteract the change

Question 17

What happens when you change the pressure in a reversible reaction in a system in equilibrium?

Answer 17

If increased, the reaction favours the direction with less molecules, to decrease pressure,
If decreased the reaction favours the direction with more molecules, to increase pressure.