Topic 6 - The rate and extent of chemical changes

Question 1

rate of reaction =

Answer 1

rate of reaction = amount of reactant used (product formed) / time

Question 2

What 2 units can be given to the rate of reaction?

Answer 2

g/s
cm^3/s

Question 3

Name the 5 factors that affect the rate of reaction

Answer 3

1. pressure of reacting gases
2. concentration of reactants
3. surface area of solid reactants
4. temperature
5. presence of catalysts

Question 4

How does increasing the pressure of reacting gases affect the rate of reaction?

Answer 4

increasing the pressure means that the same number of particles will now occupy a smaller volume which leads to more frequent successful collisions between reacting particles and an increase in the rate of reaction.

Question 5

How does increasing the concentration of reactants in a solution affect the rate of reaction?

Answer 5

Increasing the concentration increases the rate of reaction because there are a greater number of particles in the same volume to react which means that more frequent successful collisions between particles will occur.

Question 6

How does increasing the temperature affect the rate of reaction?

Answer 6

increasing the temperature increases the kinetic energy of particles and increases the energy of each collision resulting in more frequent successful collisions between reacting particles. this means the rate of reaction increases

Question 7

How does increasing the surface area of reactants affect the rate of reaction?

Answer 7

increasing the surface area of solid reactants increases the number of particles exposed and available to react which increases the frequency of collisions and rate of reaction

Question 8

How does the presence of catalysts affect the rate of reaction?

Answer 8

They increase the rate of reaction by providing an alternate reaction pathway with lower activation energy. they do this without being used up.

Question 9

What elements are most catalysts?

Answer 9

transition metals or there compounds

Question 10

True or false:
Catalysts can be reused

Answer 10

true

Question 11

Why do catalysts eventually need to be replaced?

Answer 11

they can become poisoned by impurities in the reaction

Question 12

What type of catalysts are enzymes?

Answer 12

biological
(They work in biological systems)

Question 13

What is ‘collision theory’ ?

Answer 13

chemical reactions can occur only when particles collide with eachother with sufficient energy and at the right orientation. The more frequent collisions, the higher the rate of reaction

Question 14

What is activation energy?

Answer 14

the minimum amount of energy required for particles to react.

Question 15

what is a reversible reaction?

Answer 15

the products of the reaction can react to produce the original reactants

Question 16

The direction of the reaction can be changed by changing the __________

Answer 16

conditions (e.g forward hot backward cool)

Question 17

True or false:
reversible reactions never reach equilibrium

Answer 17

FALSE
REVERSIBLE REACTIONS WILL REACH EQUILIBRIUM

Question 18

What is dynamic equilibrium?

Answer 18

Dynamic equilibrium is when the rate of the forward reaction is equal to the rate of the reverse reaction in a closed sytem and the concentration of the reactants and products remain constant.

Question 19

What is an example of a reversible reaction?

Answer 19

Hydrated copper sulfate (blue) —– anhydrous copper sulfate (white) + water

Question 20

In this reversible reaction:
Hydrated copper sulfate (blue) —– anhydrous copper sulfate (white) + water
The forward reaction is endothermic. Is the reverse reaction endothermic or exothermic?

Answer 20

exothermic

Question 21

What is Le Chatelier’s principle?

Answer 21

If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change

Question 22

What is Le Chatelier’s principle?

Answer 22

If you change the conditions of a reversible reaction, the system will try to counteract the change.