7 Chemical Reactions

Question 1

When does a reaction take place

Answer 1

when particles collide with a certain amount of energy

Question 2

What does a rate of reaction depend on (2)

Answer 2

Reacting particles must have the correct geometry

Particles must collide with sufficient energy

Question 3

Why does the rate of reaction slow down over time? (2)

Answer 3

As the reaction progresses, the concentration of reactants decreases

This reduces the frequency of collisions, slowing down the reaction

Question 4

How would a graph of a reaction look like?

Answer 4

u know it bro

Question 5

What are the two ways the rate of reaction can be measured (2)

Answer 5

how quickly a reactant is being used up

how quickly products are being formed

Question 6

Eqt for average rate of reaction

Answer 6

change in quantity/ change in time

Question 7

Define activation energy

Answer 7

minimum amount of energy required for a chemical reaction to take place

Question 8

What happens when particles collide with energy lower than the activation energy

Answer 8

successful collision will not occur and the particles will not react

Question 9

Why do reactant particles have to meet the activation energy (2)

Answer 9

To break old bonds of the reactant particles, in order to form new bonds of the products

Breaking bonds is an endothermic process and so requires energy to be put into the system

Question 10

Define collision geometry

Answer 10

position and co-ordination of particles as they collide

Question 11

What are the four factors that can speed up a chemical reaction (4)

Answer 11

Concentration

Temperature

Particle size/surface area

Use of catalyst

Question 12

Why does increasing concentration increase rate of reaction

Answer 12

there are more particles that can collide together and react

Question 13

Correlation between concentration and rate of reaction

Answer 13

higher the concentration, higher the rate of reaction

Question 14

Temperature is a measure of what?

Answer 14

measure of how much kinetic energy reactant particles have

Question 15

Relationship between temperature and rate of reaction

Answer 15

higher the temperature, the higher the rate of reaction

Question 16

Why do particles at higher temperature react at a faster rate (2)

Answer 16

Higher temperature particles have more kinetic energy and so move about more

Due to the particles moving, there is a greater chance of the particles colliding and so reaction happens faster

Question 17

Relationship between particle size and surface area

Answer 17

smaller the particle size, the greater the surface area

Question 18

Why are small particle sizes potentially dangerous in industry (2)

Answer 18

Incredibly fine particles have large surface area

If they catch fire, the rate of combustion will be very fast, leading to dust explosions

Question 19

Dangers in coal mines involving concentration and temperature (3)

Answer 19

At high concentrations, methane (flammable gas) can form an explosive mixture with air

This is because as there are more reactants colliding, there is more heat energy, this leads to an increase in temperature, leading to higher kinetic energy. This means particles have sufficient energy to collide

This further increases the temperature of the mixture until, eventually, the reaction mixture explodes.

Question 20

Define catalyst

Answer 20

substance that can be used to increase the rate of reaction without being used up and can be recovered unchanged at the end of a reaction

Question 21

catalysts are said to be “______ ______”

Answer 21

reaction specific

Question 22

What does a catalyst do to the activation energy

Answer 22

lowers activation energy

Question 23

Define oxidation

Answer 23

gain of electrons

Question 24

Define reduction

Answer 24

loss of electrons

Question 25

How can redox equations be formed

Answer 25

combining individual oxidation and reduction equations

Question 26

Know about redox equations

Answer 26

ok

Question 27

Define oxidising agent

Answer 27

substance which accepts electron

Question 28

Define reducing agent

Answer 28

substance which donates electrons

Question 29

What determines the effectiveness of reducing/oxidising agents

Answer 29

Reactivity Series

Question 30

Where are the strongest reducing agents found

Answer 30

top of reactivity series as they easily lose/donate electrons

Question 31

Where are the strongest oxidising agents found

Answer 31

bottom of reactivity series as they are better at accepting electrons

Question 32

What does an oxidation state represent

Answer 32

How many electrons an atom loses or gains to become an ion