C8

Question 1

What is rate of reaction?

Answer 1

A measure of how quickly a reactant is used up, or a product formed.

Question 2

What are the two things required for a chemical reaction to occur?

Answer 2

• Reactant particles must collide with each other

- The particles must have enough energy for them to react

Question 3

What is a successful collision?

Answer 3

A collision between reactant particles that has enough energy for a reaction to happen.

Question 4

What is activation energy?

Answer 4

It is the minimum amount of energy needed for a collision to be successful.

Question 5

How do you calculate the rate of reaction?

Answer 5

1. Quantity of reactant used * time taken

2. Quantity of product formed * time taken

Question 6

On graphs the gradient of the line is usually equal to…

Answer 6

The rate of reaction.

Question 7

What are the units for rate usually?

Answer 7

Cm3/s
Cm3/min
Mol/s

Question 8

If the concentration of a reacting solution or the pressure of a reacting gas is increased what happens to the rate of reaction?

Answer 8

The reactant particles become more crowded so the frequency of collision between the reactant particles increases. Therefore the rate of reaction increases.

Question 9

What doesnt happen to the particles no matter the conditions?

Answer 9

The mean energy if the particles doesnt change.

Question 10

The steeper the tangent…

Answer 10

The faster the reaction.

Question 11

If a large lump is ground into a powder what happens?

Answer 11

Its total volume stays the same
The area of exposed surface increases
The surface area to volume ratio increases

Question 12

What happens to the rate of reaction if surface area to volume ratio is increased?

Answer 12

More reactant particles are exposed at the surface so the frequency of successful collisions between the particles increases. Therefore increasing rate of reaction.

Question 13

A faster reaction on a graph will…

Answer 13

Give a steeper line and finish sooner

Question 14

What happens to the rate of reaction as temperature increases?

Answer 14

The reactant particles move more quickly and the energy of the particles increases, so the frequency and proportion of successful collisions between the particles increases. Therefore the rate of reaction increases.

Question 15

What is a catalyst?

Answer 15

It is a substance that…

• speeds up the rate of reaction
• does not alter the products of the reaction
• is not chemically changed or used up at the end of the reaction

Question 16

How do catalysts work?

Answer 16

They provide an alternate pathway that has a lower activation energy than the uncatalysed reaction. This doesnt change the frequancy of collision but it does change the frquency of successful collisions as the particles have greater energy than the activation energy.

Question 17

What is a reversable reaction?

Answer 17

A chemical reaction where the products of the reaction can react together to produce the original reactants and vice versa.

Question 18

What may happen to the reaction mixtures reactants and products if the conditions are changed?

Answer 18

Their proportions may be changed.

Question 19

If a reaction is exothermic in one direction it will be…

Answer 19

Endothermic in the other direction (the same amount of energy is transferred in both forward and reverse reactions).

Question 20

When will a reversible reaction reach dynamic equilibrium?

Answer 20

When it is in a closed system.

Question 21

What are the properties of reversible reactions when they reach dynamic equilibrium?

Answer 21

• the forward and backward reactions are still happeningbut they both have the same rate of reaction.
• the concentration of all reacting substances remain constant.

Question 22

If the forward reaction is exothermic, when temperature increases…. and when temperature decreases…

Answer 22

As temperature increases the amount of product formed decreases
As temperature decreases the amount of product formed increases

Question 23

If the forward reaction is endothermic, when the temperature increases… and when the temperature decreases…

Answer 23

When the temperature increases the amount of products formed also increases.
When the temperature decreases the amount of products formed also decreases.

Question 24

What is Le Châtelier’s principle?

Answer 24

Whenever a change is introduced to a system at equilibrium, the position of equilibrium shifts so as to cancel out the change.

Question 25

When does pressure not effect a reaction at equillibrium?

Answer 25

If the elements are not gases (check if correct)