Rates of Equilibrium

Question 1

How to find out the rate of reaction is

Answer 1

How quickly reactants are used up as they make products
OR
How quickly products of reaction are made

Question 2

Three techniques to collect type of data in experiments

Answer 2

1) Measure the rate at which the mass of a reaction mixture changes if the reaction gives off a gas
Put on scale, reaction mass decreases if gas is given off
2) Use gas syringe to see increasing volume of gas given off
3) Decreasing light passing through solution = cloudy

Question 3

Mean rate of reaction equation

Answer 3

Mean rate of reaction = quantity of reactant used / time
OR
Quantity of product formed / time

Question 4

Collision theory

Answer 4

Particles need to collide with enough energy to cause a reaction

Question 5

What is activation energy

Answer 5

Minimum amount of energy particles reactants must have before they can react

Question 6

What affects the rate of reaction and how?

Answer 6

Big surface area
Size of pieces of solid affects the rate of the reaction
Particles around solid can only affect surface of reactant
Small lumps or powder have larger surface area surrounded by solution = more particles exposed

Question 7

Why does raising the temperature increase the rate of reaction?

Answer 7

Particles collide more often

Particles collide with more energy

Question 8

How do particles collide more frequently?

Answer 8

Heat substance
Energy transferred to its particles
Particles move around faster
Particles collide more frequently, have more chances to react

Question 9

How do particles collide with more energy?

Answer 9

Particles move around more quickly = have more energy

Collisions are more energetic

Question 10

Rule of greater collisions

Answer 10

An increased proportion of particles exceeding the activation energy has a greater effect on rate than increased frequency of collisions

Question 11

Effect of concentration

Answer 11

More particles of reactants moving around in same volume of solution
More crowded together so more likely they will collide
Increased frequency = faster reaction

Question 12

Effect of pressure

Answer 12

Squashes gas particles more closely together
More particles of gas in given space
Increases chance to collide and react
Produces more frequency collisions

Question 13

What does a catalyst do

Answer 13

Changes rate of reactions
Products do not change
Speeds up rate of a chemical reaction by reducing energy

Question 14

Catalysts forms

Answer 14

Different catalysts needed for different reactions

Usually in form of powders, pellets or fine gauzes = biggest possible SA:V

Question 15

How catalysts work

Answer 15

Do not increase collision frequency
Increase rates of reaction by providing an alternative reaction pathway to products
higher proportion of reactant particles have sufficient energy to react

Question 16

Advantages and disadvantages of catalysts

Answer 16

-expensive
\+cheaper than having to pay for extra energy
\+help environment 
\+save money
-used multiples times
-become poisoned over certain time

Question 17

What happens in a reversible reaction

Answer 17

Products of reaction can react to make original reactants

Question 18

What is the reverse reaction if the forward reaction is exothermic?

Answer 18

Endothermic

Question 19

Stages of a closed system reaction

Answer 19

1) reactants only at start of reaction
2) rate of forward reaction is greater than reverse reaction
3) rate of reverse reaction increases as products build up and rate of forward slows as reactants get used up
4) eventually the rates of the forward and reverse reaction are equal

Question 20

Is there a change in a reaction in reactants and products?

Answer 20

No change

Question 21

Equilibrium rule

Answer 21

At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction

Question 22

La Chatelier’s Principle and who uses it

Answer 22

Change the conditions introduces a system at equilibrium, position of equilibrium shifts to cancel out change
Industrial chemists use it to find the perfect conditions to give as much product as possible

Question 23

What happens if the forward reaction produces more/fewer gas molecules?

Answer 23

More molecules of gas:
Increase pressure = decreases amount of products formed
Decrease pressure = increases amount of products formed
Fewer molecules of gas:
Increase pressure = increases amount of products
Decrease pressure = decrease amount of products

Question 24

What happens in a reversible reaction changes the number of gas molecules?

Answer 24

Altering pressure affects equilibrium

More molecules of gas on one side of equation

Question 25

Where does equilibrium shift

Answer 25

In favour of the reaction that produces fewer gas molecules | E.g. 2NO2 -> N2O4 (shifts to right because only has 1 as big number at front not 2)

Question 26

What happens to the equilibrium is there is an equal number of molecules of gas on both sides?

Answer 26

Changing pressure has no effect on the composition of the equilibrium mixture

Question 27

Temperature and equilibrium

Answer 27

Closed system = no substances are added or taken away from mixture Relative amounts of reactants and products in a reversible reaction at equilibrium depend on the temperature

Question 28

What happens if the forward reaction is exothermic/endothermic?

Answer 28

Forward reaction is exothermic: Increase in temperature = decreases the amount of products formed Decrease in temperature = increases the amount of products formed Endothermic: Increase in temperature = increases amount of products formed Decrease in temperature = decreases the amount of products formed

Question 29

What happens to equilibrium if temperature is increased?

Answer 29

Temperature increases = equilibrium shifts to reduce temperature Endothermic is forward = equilibrium favours reverse reaction (exothermic)