Rate of reaction

Question 1

Rate of reaction

Answer 1

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

Question 2

For a chemical reaction to happen what must be true (collision theory)

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 that produces a reaction

Question 4

Equations to measure mean rate of reaction

Answer 4

Quantity of reactant used / time taken

Quantity of product formed / time taken

Question 5

If a reacting gas increases in pressure explain what will happen (3)

Answer 5

The reactant particles become more crowded

The frequency of collisions between reactant particles increase

The rate of reaction increases

Question 6

If a reacting gas increases in concentration explain what will happen (3)

Answer 6

The reactant particles become more crowded

The frequency of collisions between reactant particles increase

The rate of reaction increases

Question 7

How to calculate the rate of reaction from a tangent formulae

Answer 7

Rate of reaction = change in mass or volume of a product / change in time

Question 8

Advantages of turning lumps into powders

Answer 8

Its total vol stays the same

Area of exposed sf area increase

The sf area to vol ratio increases

Question 9

Advantages of turning lumps into powders

Answer 9

Its total vol stays the same

Area of exposed sf area increase

The sf area to vol ratio increases

Question 10

Why does a powder give greater frequency of successful collisions (3)

Answer 10

More reactant particles are exposed at the surface

The frequency of collisions between reacting particles increase

The rate of reaction increases

Question 11

If the temperature of the reaction mixture is increased how does this benefit us

Answer 11

Reactant particles move more quickly

The energy of the particles increase

The frequency of successful collisions between a reactant particles increases

The proportion of collisions which are successful increase

The rate of reaction increases

Question 12

What does a catalyst do and not do (3)

Answer 12

Does:
Increase the rate of reaction

Does not:

Alter the products of a reaction

Is not chemically changed or used up at the end of the reaction

Question 13

What does a catalyst do and not do (3)

Answer 13

Does:
Increase the rate of reaction

Does not:

Alter the products of a reaction

Is not chemically changed or used up at the end of the reaction

Question 14

Required practical - measure the production of a gas formulae required to calculate the mean rate of reaction until it stops

Answer 14

Mean rate of reaction cm^3/s = total mass of gas produced cm^3 / reaction time (s)

Question 15

Required practical - measure the production of a gas

Give me a hazard the possible harm and possible precaution

Answer 15

Hazard: hydrochloric acid, possible harm being causes skin and eye irritation, a precaution would be to wear eye protection

Hazard: Fizzing in the reaction mixture, possible harm being acidic spray or foam escaping, which may damage skin and eyes to prevent this use a large conical flask so there is plenty of space inside; do not look over the top when adding calcium carbonate

Question 16

Required practical - investigate the rate of reaction by colour change

Give me two hazards the harm they could cause and a precaution

Answer 16

Hot sodium thiosulfate solution, burns the skin, do not heat above 60c

Sulfure dioxide can cause irritation to the eyes and lungs, particular to people with asthma make sure the room is well ventilated and don’t breath directly above the flash

Question 17

Dynamic equilibrium

Answer 17

• The forward and backward reactions are still happening
• The forward and backward reactions have the same rate of reaction
• The concentrations of all reacting substances remain constant

Question 18

Equilibrium position of a reversible reaction is

Answer 18

a measure of the concentrations of the reacting substances at equilibrium

Question 19

Equation for ammonia

Answer 19

N2(g) + 3H2(g) ⇌ 2NH3(g)

Question 20

Harber process

Answer 20

1.Nitrogen extracted from air and hydrogen
obtained from natural gas are pumped
through pipes

2. Pressure of the mixture of gases is
   increased to 200 atmespheres
3. The pressured gases are heated to 450c 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 21

The position of equilibrium will be left or right if N2 and H2 are greater than the concentration of NH3

Answer 21

left

Question 22

To the right or left if the concentration of NH3 is greater than the concentrations of N2 and H2

Answer 22

right

Question 23

Le Chatelier’s principle states what

Answer 23

The equilibrium position can be changed by changing the reaction conditions through pressure, concentration and temperature

Question 24

Le Chatelier’s principle pressure states

Answer 24

If the pressure is increased in a reaction involving gases, the equilibrium position moves in the direction with the fewest molecules of gas to reduce pressure

Question 25

If pressure increased in the habour process where does the equilibrium position go left tor righ

Answer 25

right

Question 26

Le Chatelier’s principle if a temprature is increased what happens to the equilibrium position and give e.g for a temperature increase

Answer 26

Moves to counteract the change that was made. For e.g position of equilibrium moves in endothermic direction

Question 27

Le Chatelier’s principle temprature

Answer 27

In a reversible reaction, if the reaction is exothermic in one direction, it is endothermic in the other direction. Therefore if temp is increased the equilbirium pos moves in the endothermic direction

Question 28

Le Chatelier’s principle concentration

Answer 28

If the concentration of a reactant is increased the equilibrium position moves in the direction away from this reactant, and so more of the products are produced