WTM Flashcards by Abbie Graves

Define electrolysis

The decomposition of a molten or aqueous iconic compound using electricity

How well did you know this?

Not at all

Perfectly

OIL RIG

Oxidation is loss, reduction is gain

Of electrons

How well did you know this?

Not at all

Perfectly

What happens at the cathode ?

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

How well did you know this?

Not at all

Perfectly

What happens at the anode

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

How well did you know this?

Not at all

Perfectly

What happens when the ions gain or lose electrons

They because uncharged substances and are discharged form the electrolyte

How well did you know this?

Not at all

Perfectly

Write the half equation for sodium losing one electron

Na -> Na+ + e-

How well did you know this?

Not at all

Perfectly

Write the half equations for hydrogen gaining an electron

2H+ +2e- -> H2

How well did you know this?

Not at all

Perfectly

What is an electrochemical cell

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

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

Why can’t an ionic solid be electrolysed

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

How well did you know this?

Not at all

Perfectly

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

Positive metal ions are reduced to metal atoms at the cathode

How well did you know this?

Not at all

Perfectly

What happens to negative ions in electrolysis of molten ionic solids

Negative ions are oxidised to atoms or molecules at the anode

How well did you know this?

Not at all

Perfectly

What happens in the electrolysis of molten ionic solid PbBr2

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-

How well did you know this?

Not at all

Perfectly

What happens with the molten electrolyte potassium chloride KCl

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

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

How well did you know this?

Not at all

Perfectly

What happens with the molten electrolyte aluminium oxide Al2O3

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

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

How well did you know this?

Not at all

Perfectly

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

Hydrogen ions H+
Hydroxide ions OH-

From the water

How well did you know this?

Not at all

Perfectly

What happens at the cathode in the electrolysis of aqueous solution

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

How well did you know this?

Not at all

Perfectly

What happens at the anode in the electrolysis of aqueous solution

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

How well did you know this?

Not at all

Perfectly

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

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-

How well did you know this?

Not at all

Perfectly

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

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

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

How well did you know this?

Not at all

Perfectly

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

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

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

How well did you know this?

Not at all

Perfectly

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

Study These Flashcards

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

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

What does the electrolysis of copper sulfate with inert electrodes produce

Study These Flashcards

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-

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

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

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

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

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

it pulls electrons off copper atoms at the anode Cu -> Cu2+ + 2e- offering electrons at the cathode to nearby Cu2+ ions Cu2+ + 2e- -> Cu

how can copper be extracted from its ore

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

what happens when copper is purified using electrolysis

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

what colours does litmus go

red in acidic purple in neutral blue in alkaline

what colours does methyl orange

red in acidic yellow in neutral yellow in alkaline

what colour does phenolphthalein

colourless in acidic colourless in neutral pink in alkaline

what is neutralisation

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

acid + metal oxide (base)

forms a salt and water

acid + metal hydroxide (base)

salt and water

acid + metal

salt and hydrogen

acid + metal carbonate

salt + water + carbon dioxide

neutralisation reaction equation in aqueous solution

H+ + OH- -> H2O

Where do we extract hydrogen from for the haber process

From hydrocarbons from sources such as natural gas and crude oil

Where do we get nitrogen from for the haber process

The air

What are the conditions of the haber process

450 degrees 200 atmosphere pressure Iron catalyst

What happens to equilibrium if you decrease the pressure

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

What happens if you increase the direction of the haber process

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

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

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

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

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

Why is the haber process temperature at 450 degrees

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

In what condition only can equilibrium be reached

In a closed system where no products can escape

What is the mass and charge of the three atom particles

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

What charge does the nucleus have

Positive

How did Mendeleev sort the periodic table

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

How do you calculate relative formula mass

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

How do you calculate empirical formula

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

How do you calculate molecular formula from empirical formula

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

Mass calculation

Moles x relative atomic mass of molecular mass

Mass of solute

Concentration x volume

What are the properties of giant covenant structures

High mp and bp Don’t conduct electricity Insoluble

Diamond

Network of carbon atoms that form four covelant bonds | High mp

WTM Flashcards

(57 cards)