2.2 Rates of Reaction

Question 1

The Rate of Reaction

Answer 1

Is the change in concentration of a reactant or product per unit time

Question 2

What are the units for the rate of reaction?

Answer 2

moldm^-3s^-1

Question 3

Usually rate is the fastest at the … of a reaction

Answer 3

Start

Question 4

Rate decreases as the reaction proceeds because the … of the … decreases

Answer 4

Concentration
Reactants

Question 5

Collision Theory

Answer 5

For a reaction between two molecules to occur an effective collision must take place

Question 6

What is reaction rate a measure of

Answer 6

How frequently effective collisions occur

Question 7

What are the five factors that effect the rate of reaction?

Answer 7

Concentration (Pressure for gases), Temperature, Particle size, Catalysts, Light

Question 8

Why does Concentration effect the rate of reaction?

Answer 8

The increased concentration means there is an increased number of molecules in the same volume, So the distance between molecules is reduced so there is an increase in the number of collisions.

Question 9

Why does Temperature effect the rate of reaction?

Answer 9

Increasing the temperature provides the molecules with more kinetic energy so they will move faster, this means that on collision more molecules will have enough energy to react.

Question 10

Why does Particle Size effect the rate of reaction?

Answer 10

Increasing the surface area of a solid means there are more surfaces to collide with each other and the molecules will now be closer together so there is an increase in collisions per unit time leading to an increase in reaction rate

Question 11

How do Catalysts effect the rate of reaction?

Answer 11

A catalyst increases the rate of reaction without itself undergoing a permanent change

Question 12

How does light effect the rate of reaction?

Answer 12

Some reactions are much more vigorous when carried out in bright light

Question 13

Activation Energy

Answer 13

Is the minimum energy required to start a reaction by breaking bonds

Question 14

For Exothermic reactions ΔH is?

Answer 14

Negative

Question 15

For Endothermic reactions ΔH is?

Answer 15

Positive

Question 16

ENdothermic

Answer 16

ENters

Question 17

EXothermic

Answer 17

EXits

Question 18

For a successful collision to occur what two things must be true?

Answer 18

The orientation must be favourable
The molecules colliding must have enough energy

Question 19

Catalyst

Answer 19

Is a substance that increases the rate of a chemical reaction without being used up in the process, it increases the rate of reaction by providing an alternative route of lower activation energy.

Question 20

Short version for catalyst

Answer 20

Reduces the required activation energy in a reaction

Question 21

Homogeneous Catalyst

Answer 21

Is in the same physical state as the reactants

Question 22

Heterogeneous Catalyst

Answer 22

Is in a different physical state from the reactants

Question 23

Name three industry’s Enzymes are used in?

Answer 23

Dairy industry (Rennin)
Brewing industry (Yeast and Amylase)
Washing powders and detergents (Lipase and Protease)

Question 24

What are the benefits of using Enzymes?

Answer 24

Lower temperatures and pressures can be used.
They do not harm fabrics or food.
They are biodegradable.
They often allow reactions to take place which form pure products with no side reactions.

Question 25

What are the four ways to measure the rate of chemical reaction?

Answer 25

Change in gas volume (Gas syringe)
Change in pressure (Manometer)
Change in mass (Weighing Scales)
Colorimetry