C5.6- Rate And Extent Of Chemical Change

Question 1

What is rate of reaction a measure of?

Answer 1

How quickly a reactant is used up or a product is formed.

Question 2

How can rate of reaction be calculated?

Answer 2

Quantity of reactant used/taken or quantity of product form/time taken

Question 3

What are the units for rate of reaction?

Answer 3

g/s
cm3/s
mol/s

Question 4

What does collision theory state?

Answer 4

Chemical reactions only occur when reacting particles collide with each other, and with sufficient energy to react

Question 5

What are the five factors talked about in collision theory?

Answer 5

Concentration
Temperature
Pressure
Surface area.
Catalyst

Question 6

What factors affect the frequency of collisions?

Answer 6

Concentration
Temperature
Pressure
Surface area

Question 7

What factors affect how successful each collision is?

Answer 7

Temperature
Catalyst

Question 8

Explain how temperature affects the rate of reaction

Answer 8

The higher the temperature, the greater of the rate of reaction. As the kinetic energy of the reacting particles increases they move faster. This would increase the frequency of collisions which would lead to more successful collisions. More energetic collisions will also provide sufficient activation energy.

Question 9

Explain how pressure will affect the rate of reaction

Answer 9

The smaller, the volume the higher, the pressure and the faster the rate of reaction. This is because as the reacting particles are closer together, there are more frequent collisions between the reacting particles.

Question 10

Explain how surface area will affect the rate of reaction

Answer 10

The larger the surface area to volume ratio, the greater the rate of reaction. As more reacting particles are exposed and able to collide this would increase the frequency of collisions at the surfaces.

Question 11

What is activation energy?

Answer 11

The minimum amount of energy for a collision to be successful

Question 12

What does a catalyst do and how does it do it?

Answer 12

Lowest the activation energy for a reaction by providing an alternative pathway for a reaction to happen through

Question 13

What is a reversible reaction?

Answer 13

A reversible chemical reaction is, when the products of the reaction can react to produce the original reactants

Question 14

What are the energy changes in reversible reactions?

Answer 14

If one reaction is endothermic, the other is exothermic
The same amount of energy is transferred forward as is backwards

Question 15

What is Le Chateliers principle?

Answer 15

If a dynamic equilibrium is disturbed by changing the conditions, the reaction will move to counteract the change

Question 16

What is dynamic equilibrium?

Answer 16

When the Ford rate of a reversible reaction is equal to the backward rate of reaction

Question 17

Reaction is exothermic in the forward direction and endothermic in the backward direction. If I heat the system, will I get more products or more reactant?

Answer 17

Reaction will try and counteract it by increasing the backward reaction as it is endothermic, and they store more energy in their bonds and therefore increased the mass of the reactants.

Question 18

If I increase the concentration of the reactants, how will the equilibrium shift?

Answer 18

Products will be favoured and their mass will increase

Question 19

How will the equilibrium shift if I increase pressure?

Answer 19

The equilibrium will shift to reduce the pressure by favouring the side with fewer gas molecules

Question 20

Does adding a catalyst shift the equilibrium?

Answer 20

No, it just increases the rate of how quickly equilibrium is reached

Question 21

What is the equation for the Haber process?

Answer 21

N2+3H2=\2NH3

Question 22

What catalyst, pressure and temperature does the Haber process happen at?

Answer 22

200 atm pressure
450° C.
Iron catalyst

Question 23

Why are these pressures and temperatures used in the Haber process?

Answer 23

Pressure– if too high safety issue, not as much change/benefit
Temperature – too high and lower percentage shield, higher temperature means faster reaction

Question 24

Describe the Haber process

Answer 24

1. nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes
2. the pressure of the mixture of gases is increased to 200 atmospheres
3. the pressurised gases are heated to 450°C and passed through a tank containing an iron catalyst
4. the reaction mixture is cooled so that ammonia liquefies and can be removed
5. unreacted nitrogen and hydrogen are
   recycled

Question 25

What is three compounds are typically found in fertilisers?

Answer 25

Nitrogen
Phosphorus.
Potassium

Question 26

Why must fertiliser compounds be soluble in water?

Answer 26

So root hair cells can absorb them

Question 27

What two irons are sources of soluble nitrogen?

Answer 27

Ammonium ions NH4+
Nitrate ions NO3-

Question 28

What ions are soluble sources of phosphorus?

Answer 28

Phosphate ions, PO43-

Question 29

What are the four common fertiliser compounds?

Answer 29

Ammonium nitrate NH4NO3
Ammonium sulphate (NH4)2S04
Ammonium phosphate (NH4)3PO4
Potassium nitrate KNO3

Question 30

What reacts with ammonia to make ammonium nitrate?

Answer 30

Nitric acid

Question 31

What reacts with ammonia to make ammonium sulphate?

Answer 31

Sulphuric acid

Question 32

What reacts with ammonia to make ammonium phosphate?

Answer 32

Phosphoric acid
H3PO4