Rates of reaction

Question 1

What are the variables that affect rates of reaction?

Answer 1

Temperature
Concentration
Surface area
Pressure

Question 2

What has to happen for a reaction to take place?

Answer 2

Collisions with activation energy

Question 3

What is the activation energy?

Answer 3

The lowest amount of energy that collision particles must have to react together

Question 4

What will happen if you increase one of the variables?

Answer 4

The rate of reaction will increase as the frequency of collisions will increase

Question 5

What happens if the concentration is high?

Answer 5

There is more particles per unit volume so there is more frequent collisions so it is faster

Question 6

What happens if the concentration is low?

Answer 6

There is fewer particles so there is less collisions so it is slower

Question 7

If the particles are smaller is the surface area bigger?

Answer 7

Yes as the SA:Vol is bigger

Question 8

What happens if the surface area is bigger?

Answer 8

There is more frequent collisions so it is faster

Question 9

What happens if the pressure is high?

Answer 9

The particles are closer together so there is more collisions so it is faster

Question 10

What happens if the pressure is low?

Answer 10

The particles are further apart so there is less collisions so the rate is slower

Question 11

What happens if the temperature is higher?

Answer 11

The particles have more energy so they move faster, colliding so more of these collisions have the activation energy so it is faster

Question 12

What happens if the temperature is lower?

Answer 12

The particles have less energy so they move slower, colliding less so less of these collisions have the activation energy so it is slower

Question 13

What is a catalyst?

Answer 13

A substance that speeds up the rate of reaction by lowering the activation energy of the reaction

Question 14

How do catalysts lower the activation energy?

Answer 14

By providing an alternative reaction pathway

Question 15

Are catalysts ever used up?

Answer 15

no so they can be reused

Question 16

In reversible reactions if one way is exothermic, what will the other way be?

Answer 16

Endothermic

Question 17

What is Le Chatelier’s Principle?

Answer 17

The idea if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract the change

Question 18

What can Le Chatelier’s Principle be used to do?

Answer 18

To predict the effect of any changes you make to a reaction system

Question 19

What will happen to equilibrium if you decrease the temperature?

Answer 19

It will move in the exothermic direction to produce more heat so there will be more products in the exothermic side and fewer in the endothermic

Question 20

What will happen to equilibrium if you increase the temperature?

Answer 20

It will move in an endothermic direction to decrease the temperature so there will be more products on the endothermic side and fewer on the exothermic

Question 21

What will happen to equilibrium if you increase the pressure?

Answer 21

Equilibrium tries to reduce it so moves in the direction of fewer molecules of gas

Question 22

When does changing the pressure only ever affect?

Answer 22

When an equilibrium involves a gas

Question 23

What will happen to equilibrium if you decrease the pressure?

Answer 23

Equilibrium tries to increase so moves in the direction of more molecules of gas

Question 24

What happens when you change the concentration of either the reactants?

Answer 24

The system will no longer be at equilibrium

Question 25

What will happen to equilibrium if you increase the concentration?

Answer 25

The system tries to decrease it by making more products

Question 26

What will happen to equilibrium if you decrease the concentration?

Answer 26

The system tries to increase it by reducing the amount of reactants