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WTM Flashcards

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1
Q

Define electrolysis

A

The decomposition of a molten or aqueous iconic compound using electricity

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2
Q

OIL RIG

A

Oxidation is loss, reduction is gain

Of electrons

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3
Q

What happens at the cathode ?

A

The positive cations in the electrolyte move towards the negative cathode and are reduced (gain electrons)

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4
Q

What happens at the anode

A

The negative anions in the electrolyte move towards the positive anode and are oxidised (lose electrons)

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5
Q

What happens when the ions gain or lose electrons

A

They because uncharged substances and are discharged form the electrolyte

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6
Q

Write the half equation for sodium losing one electron

A

Na -> Na+ + e-

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7
Q

Write the half equations for hydrogen gaining an electron

A

2H+ +2e- -> H2

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8
Q

What is an electrochemical cell

A

A circuit made up of the anode, cathode electrolyte, a power source and the wires that connect the two electrodes

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9
Q

How do you set up an electrochemical cell if the electrolyte is a solution

A

Get two inert electrodes like graphite or platinum and clean the surfaces of them using emery paper. Be careful now to not touch the surface of them to prevent grease transfer. Place both electrodes into a beaker if your electrolyte (50cm2) connect the electrodes to the power supply using crocodile clips and wires and when you turn the power supply on a current with flow through the cell

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10
Q

How do you set up an electrochemical cell if you substance is a molten ionic substance

A

Put your solid ionic substance into a crucible and heat with a Bunsen unto the solid is molten you should do this in a fine cupboard to avoid releasing toxic fumes into the room. Once the solids molten dip two clean inert electrodes into the electrolyte and connect to power supply

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11
Q

Why can’t an ionic solid be electrolysed

A

Because their ions are in fixed positions and can’t move

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12
Q

What happens to positive metal ions in the electrolysis of molten ionic solids ?

A

Positive metal ions are reduced to metal atoms at the cathode

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13
Q

What happens to negative ions in electrolysis of molten ionic solids

A

Negative ions are oxidised to atoms or molecules at the anode

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14
Q

What happens in the electrolysis of molten ionic solid PbBr2

A

You see a brown vapour of bromine gas at the anode and a silver coloured liquid at the cathode as a molten lead is formed

Pb2+
Br-

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15
Q

What happens with the molten electrolyte potassium chloride KCl

A

Potassium at the cathode
K+ + e- -> K

Chlorine at anode
2Cl- -> Cl2 + 2e-

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16
Q

What happens with the molten electrolyte aluminium oxide Al2O3

A

Aluminium at the cathode
Al3+ + 3e- -> Al

Oxygen at the anode
2O2- -> O2 + 4e-

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17
Q

What else is present as well as the ions from the ionic compound in the electrolysis of aqueous solutions

A

Hydrogen ions H+
Hydroxide ions OH-

From the water

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18
Q

What happens at the cathode in the electrolysis of aqueous solution

A

At the cathode if H+ ions and metal ions are present, hydrogen gas will be produced if the metal is more reactive than hydrogen
If the metal is less reactive than the hydrogen then a solid layer of the pure metal will be produced instead

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19
Q

What happens at the anode in the electrolysis of aqueous solution

A

At the anode if OH- and halide ions are present molecules of chlorine, bromine or iodine will be formed. If no halide ions are present the oxygen will be formed

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20
Q

A solution of sodium chloride (NaCl) contains four different ions Na+, Cl-, OH- and H+

A

At the cathode hydrogen has will be produced because it is less reactive than sodium metal
2H+ + 2e- -> H2

Chloride ions are present in the solution so at the anode chlorine gas is produced
2Cl- -> Cl2 + 2e-

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21
Q

What will be produced in the electrolysis of aqueous electrolyte copper chloride CuCl2

A

Copper at the cathode
Cu2+ + 2e- -> Cu

Chlorine at the anode
2Cl- -> Cl2 + 2e-

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22
Q

What will be produced in the electrolysis of aqueous electrolyte sodium sulfate Na2 SO4

A

Hydrogen at the cathode
2H+ + 2e- -> H2

Oxygen at the anode
4OH- -> O2 + 2H2O + 4e-

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23
Q

What will be produced in the electrolysis of aqueous electrolyte water acidified with sulfuric acid H2O/H2SO4

A

Hydrogen at the cathode
2H+ + 2e- -> H2

Oxygen at the anode
4OH- -> O2 + 2H2O + 4e-

24
Q

What does the electrolysis of copper sulfate with inert electrodes produce

A

Copper is less reactive than hydrogen so forms at the cathode
Cu2+ + 2e- -> Cu

They aren’t any halide ions present so oxygen and water are produced at the anode (you see bubbles of gas forming)
4OH- -> O2 + 2H2O + 4e-

25
Q

what happens when you electrolyse copper sulphate using non-inert copper electrodes

A

as the reaction continues the mass of the anode will decrease and the mass of the cathode will increase because the copper is transferred from the anode to the cathode. the reaction takes a while so leave the cell running for 30 minutes so you get a good change in mass. You can then measure the change in the mass of your electrodes by calculating their difference in mass before and after the experiment
make sure electrodes are dry before weighing them to give an accurate mass

26
Q

what happens if you increase the current when using non-inert electrodes

A

if you increase the current you will increase the rate of electrolysis which means there will be a bigger difference between the mass of the two electrodes after the same amount of time

27
Q

how the does the electrical supply act in electrolysis of copper sulphate using non-inert electrodes

A

it pulls electrons off copper atoms at the anode
Cu -> Cu2+ + 2e-

offering electrons at the cathode to nearby Cu2+ ions
Cu2+ + 2e- -> Cu

28
Q

how can copper be extracted from its ore

A

by reduction with carbon but copper made this way is impure. Electrolysis is used to purify it - this method use an electrochemical cell with copper electrodes

29
Q

what happens when copper is purified using electrolysis

A

the anode starts off as being a big lump of impure copper the electrolyte is copper (II) sulphate solution and the cathode starts off as a thin piece of pure copper

the impure copper anode is oxidised dissolving the electrolyte to form copper ions
the copper ions are reduced at the pure copper cathode and add it to it as a layer of pure copper

any impurities from the impure copper anode sink to the bottom of the cell forming a sludge

30
Q

what colours does litmus go

A

red in acidic
purple in neutral
blue in alkaline

31
Q

what colours does methyl orange

A

red in acidic
yellow in neutral
yellow in alkaline

32
Q

what colour does phenolphthalein

A

colourless in acidic
colourless in neutral
pink in alkaline

33
Q

what is neutralisation

A

the reaction between an acid and a base
and it produces salt and water

HCl + NaOH -> NaCl + H2O

in the product the conc of hydrogen ions is equal to the hydroxide ions

34
Q

acid + metal oxide (base)

A

forms a salt and water

35
Q

acid + metal hydroxide (base)

A

salt and water

36
Q

acid + metal

A

salt and hydrogen

37
Q

acid + metal carbonate

A

salt + water + carbon dioxide

38
Q

neutralisation reaction equation in aqueous solution

A

H+ + OH- -> H2O

39
Q

Where do we extract hydrogen from for the haber process

A

From hydrocarbons from sources such as natural gas and crude oil

40
Q

Where do we get nitrogen from for the haber process

A

The air

41
Q

What are the conditions of the haber process

A

450 degrees
200 atmosphere pressure
Iron catalyst

42
Q

What happens to equilibrium if you decrease the pressure

A

The equilibrium will move in the exothermic direction to produce more heat

43
Q

What happens if you increase the direction of the haber process

A

The equilibrium will move in the endothermic direction to absorb the extra heat

44
Q

What happens to equilibrium if you increase and decrease the pressure (only in a gas)

A

The equilibrium will move to the side that has the fewer moles to reduce pressure

If you decrease the pressure the equilibrium will move towards the side that has more moles of gas to increase pressure

45
Q

What happens to the equilibrium if you decrease and increase the concentration

A

If you increase the concentration of the reactants the equilibrium will move to the right to use up the reactants making more products

If you increase the concentration of the products the equilibrium will move to the left to use up the products making more reactants

Decreasing does the opposite

46
Q

Why is the haber process temperature at 450 degrees

A

So it is hot enough for the reaction to take place but not too hot so the equilibrium won’t shift so you get the maximum yield

47
Q

In what condition only can equilibrium be reached

A

In a closed system where no products can escape

48
Q

What is the mass and charge of the three atom particles

A

Proton 1. +1
Neutron. 1. 0
Electron. 1/1835. -1

49
Q

What charge does the nucleus have

A

Positive

50
Q

How did Mendeleev sort the periodic table

A

Groups and periods based on their number of electrons and chemical properties

51
Q

How do you calculate relative formula mass

A

Find the relative atomic masses of each atom and add them up

52
Q

How do you calculate empirical formula

A

Put it into a ratio and simplify the ratio by dividing them by the largest number that goes into each

53
Q

How do you calculate molecular formula from empirical formula

A

Find Mr by adding up all of the relative atomic masses
Divide the Mr of the compound by the Mr of the empirical formula
Multiply everything in empirical formula by the result

54
Q

Mass calculation

A

Moles x relative atomic mass of molecular mass

55
Q

Mass of solute

A

Concentration x volume

56
Q

What are the properties of giant covenant structures

A

High mp and bp
Don’t conduct electricity
Insoluble

57
Q

Diamond

A

Network of carbon atoms that form four covelant bonds

High mp

Chemistry (13 decks)

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