C2.4

Question 1

What is a catalyst?

Answer 1

A substance that increases the rate of a chemical reaction without being altered or used up

Question 2

What are the factors that affect the rate of a reaction?

Answer 2

~ Temperature
~ Concentration of solutions
~ Pressure of gases
~ Surface area of solids
~ Use of a catalyst

Question 3

What is the activation energy?

Answer 3

The minimum amount of energy required to cause a reaction

Question 4

What are the particles like in a low temperature mixture?

Answer 4

~ Move slow

~ Less collisions as they have less energy so less particles can collide successfully

Question 5

What are the particles like in a high temperature mixture?

Answer 5

~ Move fast

~ More collisions as they have more energy so more particles can collide successfully

Question 6

What causes chemical reactions?

Answer 6

Reacting particles colliding with each other with sufficient energy

Question 7

What are the particles like in low concentrations?

Answer 7

~ Less of them in that volume
~ Spread out
~ Less collisions

Question 8

What are the particles like in high concentrations?

Answer 8

~ More of them in that volume
~ Close together
~ More collisions

Question 9

What unit are concentrations of solutions given in?

Answer 9

Mol/dm^3

Question 10

What does a decrease in surface area of a solid mean?

Answer 10

~ Fewer particles so less successful collisions

~ Less collisions = slower reaction

Question 11

What does an increase in surface area of a solid mean?

Answer 11

~ More particles so more successful collisions

~ More collisions = faster reaction

Question 12

What do catalysts lower?

Answer 12

The activation energy

Question 13

What’s one way that a catalyst lowers the activation energy?

Answer 13

By providing a surface for molecules to attach to, therefore increasing the chance of them colliding

Question 14

What are some processes that involve catalysts?

Answer 14

~ Cracking hydrocarbons

~ The manufacture of ammonia

Question 15

Why is increasing the rate of chemical reactions important in industry?

Answer 15

Because it helps to reduce costs

Question 16

What does lowering the activation energy mean for the industry?

Answer 16

Reactions can happen at a lower temperature, which reduces costs

Question 17

How can the rate of a chemical reaction be found?

Answer 17

Time

Question 18

How could you measure the amount of product formed in a decomposition reaction?

Answer 18

~ Weighing the mixture before and after the reaction

~ Or using a gas syringe to measure the volume of gas produced

Question 19

What is the test for oxygen?

Answer 19

Inserting a glowing splint into a jar of collected gas which will relight in the presence of oxygen

Question 20

Why could one reaction be faster than another?

Answer 20

It could have...
~ A greater surface area 
~ A higher temperature 
~ A higher concentration 
~ Used a catalyst

Question 21

How do measure the rate of reaction between acid and sodium thiosulphate?

Answer 21

By drawing a cross on paper, placing it under the glass and measuring the time it takes to disappear
(The solution goes from clear to cloudy)

Question 22

What happens when the reactants have been used up?

Answer 22

The volume of gas/mass of product collected will stay the same (a horizontal line on a graph)

Question 23

What does increasing the pressure do to the particles?

Answer 23

~ It reduces the space they have
~ Particles are closer together
~ More successful collisions

Question 24

What are some examples of a catalyst?

Answer 24

~ Manganese oxide
~ Iron
~ Platinum
~ Nickel

Question 25

What's a problem with increasing the temperature or pressure to speed up a reaction?

Answer 25

Costs money

Question 26

Different catalysts are used...

Answer 26

...for different reactions

Question 27

What are advantages of using catalysts?

Answer 27

``` ~ Less energy used ~ Speeds up reactions ~ Reusable ~ Lower production cost ~ Only needed in small amounts ```

Question 28

What are disadvantages of using catalysts?

Answer 28

~ Can be toxic | ~ Can be expensive

Question 29

Why do powders react faster than larger pieces of solid?

Answer 29

Because they have a larger surface area to volume relation

Question 30

What does a gas syringe measure?

Answer 30

The volume of gas produced