Higher Chemistry Unit 3- equilibria and redox

Question 1

what are the rates like at equilibrium

Answer 1

the rates are equal

Question 2

what are concentrations like at equilibrium

Answer 2

the concentrations are constant

Question 3

what is the symbol used to show a reversible reaction

Answer 3

arrow going forward and backward

Question 4

in what types of reactions can equilibrium form

Answer 4

reactions in which the reversible reaction occurs spontaneously.

Question 5

what is equilibrium

Answer 5

where the reaction continues to go backwards and forwards at the same rate and so the concentration of reactants and products appear to remain constant

Question 6

what does a graph of concentration and time look like for a reaction approaching equilibrium

Answer 6

the concentration of the reactants decreases and the concentration of the products increases. when they reach equilibrium the lines become horizontal lines and so the concentration is constant.

Question 7

What does a graph of rate and time look like for a reaction approaching eqm

Answer 7

the forward rate decreases and the reverse rate increases. when the graph reaches eqm the two lines co-inside and the rates become constant and equal

Question 8

what does eqm lies to the left mean

Answer 8

when the concentration of reactants is greater tan the concentration of products.

Question 9

what dos eqm lies to the right mean

Answer 9

when the concentration of products is greater than the concentration of the reactants

Question 10

what does a graph of eqm lies to the left look like

Answer 10

the concentration of reactants levels out higher than that of the products

Question 11

what does a graph of eqm lies to the right look like

Answer 11

the concentration of reactants is initially higher but it decreases as the concentration of the products increases and when eqm is achieved the concentration of products is higher. (looks like a fish)

Question 12

what is the basic eqm equation

Answer 12

A + B <=> C + D

Question 13

does the reaction stop when eqm is achieved

Answer 13

no

Question 14

does eqm consist 50% reactants and 50% products?

Answer 14

no

Question 15

what is le Chatelier’s principle

Answer 15

if a system at equilibrium is subjected to a change, the system will adjust to oppose the effect of the change

Question 16

why is the position of the equilibrium changed in industry

Answer 16

to gain a higher yield or to increase the rate of reaction

Question 17

where does the eqm move towards when you decrease the concentration

Answer 17

eqm moves towards the thing you’re removing

Question 18

where does the eqm move toward when you increase the concentration

Answer 18

eqm moves away from the thing you’re changing

Question 19

what happens to eqm when you increase the concentration of A + B

Answer 19

you speed up the forward reaction. the eqm position moves to the right to counteract this change (more C and D are produced)

Question 20

what happens to eqm when you decrease the concentration of C + D

Answer 20

you slow down the backward reaction. this means the eqm will move to the right in order to counteract the changes (more C and D are produced)

Question 21

what happens to eqm when you increase the concentration of C and D

Answer 21

it will speed up the backwards reaction. the eqm therefore moves to the left to counteract this change (more A + B) are produced.

Question 22

what factors affect the position of eqm

Answer 22

concentration; temperature; pressure; catalyst

Question 23

what happens to eqm when you increase the temperature

Answer 23

• the reaction attempts to decrease it
• endothermic reaction is favoured
• eqm moves in the reaction of the endothermic reaction (I.e. left)

Question 24

what happens to eqm when you decrease the temperature

Answer 24

• reaction attempts to increase it
• exothermic reaction is favoured
• eqm moves in direction of exothermic reaction (i.e. right)

Question 25

how do you remove a H+ from an equation

Answer 25

add an OH- (H20)

Question 26

how do you remove an OH- from an equation

Answer 26

add an H+ (H20)

Question 27

how do you remove a silver ion from an equation

Answer 27

add a halide ion - e.g. CL^- add AgNO3 (formed precipitate)

Question 28

how do you remove a halide ion from an equation

Answer 28

add a silver ion - e.g. Ag^+ add NaCl to form precipitate

Question 29

how do you remove Ba2+

Answer 29

add a SO4^2- compound- e.g. Ba2+ + Na2SO4

Question 30

how do you remove SO4^2-

Answer 30

add a Ba^2+ compound

Question 31

what affect does removing a chemical from an equation have on the position of the eqm

Answer 31

it will affect the concentrations - eqm move from there

Question 32

if the forward reaction is exothermic the reverse reaction will be...

Answer 32

endothermic (and vice versa)

Question 33

in which state does changing the pressure affect the position of the eqm

Answer 33

only gases- ignore others

Question 34

what happens to eqm when you increase the pressure

Answer 34

- eqm attempts to decrease it | - moves to the smaller moles (total moles of each side)

Question 35

what happens to eqm when you decrease the pressure

Answer 35

- eqm attempts to increase it | - moves to larger moles (total moles of each side

Question 36

what happens to the forward and backward rates if a catalyst is added

Answer 36

the rates of both the forward and backward reactions will be increased by the same amount

Question 37

how does a catalyst affect the position of the eqm

Answer 37

it does not alter the position of equilibrium

Question 38

which bit of eqm does a catalyst affect

Answer 38

although it does not increase the percentage conversion of reactants into products it does speed up the rate of attainment of equilibrium

Question 39

what does the haber process make

Answer 39

ammonia

Question 40

what does the Ostwald process make

Answer 40

nitric acid

Question 41

what does the Contact process make

Answer 41

sulphuric acid

Question 42

what are the feedstocks of the Haber process

Answer 42

hydrogen and nitrogen

Question 43

what are the feedstocks of the Ostwald process

Answer 43

Ammonia, oxygen and water

Question 44

what are the feedstocks of the Contact process

Answer 44

sulphur and oxygen

Question 45

what are the ideal conditions for the Haber process

Answer 45

- 450*C - iron catalyst - 200 atmospheres

Question 46

what are the ideal conditions for the Ostwald process

Answer 46

- 800*C - platimun catalyst - 4-10 atmospheres

Question 47

what are the ideal conditions for the Contact process

Answer 47

- 400-450*C - V205 catalyst - 1-2 atmospheres

Question 48

what happens to the position of the eqm if you add a reactant or remove a product

Answer 48

eqm moves to right (forward reaction)

Question 49

what happens to the position of eqm if you add a product or remove a reactant

Answer 49

eqm moves to the left (backwards reaction)

Question 50

what does acid have in it which could be important in influencing the position of the eqm

Answer 50

H+ and OH-

Question 51

what is oxidation

Answer 51

the loss of electrons

Question 52

what is reduction

Answer 52

gain of electrons

Question 53

how do you remember oxidation and reduction

Answer 53

OILRIG

Question 54

what is the reducing agent

Answer 54

causes reduction, it is oxidised, loss of electrons

Question 55

what is the oxidising agent

Answer 55

causes oxidation, it is reduced, gains electrons

Question 56

what is a redox equation

Answer 56

a reaction involving both oxidation and reduction

Question 57

in an exam how will you recognise a redox equation

Answer 57

it has the element on one side; and the ion of the element on the other side

Question 58

how do you write a redox equation

Answer 58

1. write down ion electron equation for both 2. balance so the electrons are equal 3. add together omitting electrons

Question 59

what does an element need to be a good reducing agent

Answer 59

have a low ionisation energy as they need to be good at donating electrons to other substances

Question 60

what does an element need to be a good oxidising agent

Answer 60

high electronegativity as they need to be good at accepting electrons from other substances

Question 61

how do you figure out which ions are reacting in a redox equation

Answer 61

1. draw a box (like the page in the data booklet) 2. put all the ions in their position in the table 3. the arrows MUST move anti clockwise (C shape). 4. there should only be one option. if there is multiple it is the ones that are the furthest away.

Question 62

how do you recognise an oxidation equation

Answer 62

it loses electrons ( electrons are on right side of equation

Question 63

how do you recognise a reduction equation

Answer 63

it gains electrons (electrons are on the left side of the equation

Question 64

what way do you figure out which way to write the ion electron equation

Answer 64

move in a C shape. (Anticlockwise)

Question 65

what is the electrochemical series

Answer 65

it lists substances I order of how well they act as reducing/oxidising agents

Question 66

what is the reactivity like of the halogens

Answer 66

-as you go down group 7, the reactivity decreases (the lower down they are in the electrochemical series the more reactive they are)

Question 67

what is needed for a redox reaction to occur

Answer 67

the oxidising agent must be below the reducing agent | the OIL is below the RIG

Question 68

what can oxidising agents be used for

Answer 68

in the breakdown of colour compounds or to kill fungi

Question 69

what oxidising agent can break down coloured compounds

Answer 69

hydrogen peroxide- bleach, breakdown of coloured compounds; bleach wool, cotton, paper and lighten hair and teeth.

Question 70

what oxidising agent can be used to kill fungi

Answer 70

potassium permanganate - antiseptic, used to treat mild skin condition + fungal infections of the hands and feet.

Question 71

how do you figure out an ion electron equation

Answer 71

1. check the main atoms are balanced 2. check the oxygens are balanced- add water if they are not 3. check the hydrogens are balanced- at H+ if not 4. check the charges are balanced. - add electrons if not

Question 72

how do you recognise an oxidising/reducing agent in a redox equation

Answer 72

reducing agent- one being oxidised (losing e) | oxidising agent- one being reduced (gaining e)

Question 73

what group has the strongest reducing agents

Answer 73

group 1

Question 74

what group has the strongest oxidising agents

Answer 74

group 7

Question 75

give an example of a strong oxidising agent

Answer 75

hydrogen peroxide

Question 76

name an example of a gas that can be used as a reducing agent

Answer 76

carbon dioxide