paper 2

Question 1

what material is used for the electrodes in electrolysis and why

Answer 1

graphite - it can conduct electricity and it is inert

it needs to be inert so that they don’t participate in a side reaction with the electrolyte

Question 2

what is the name for the positive electrode

Answer 2

anode (BECAUSE IT ATTRACTS THE ANIONS)

Question 3

what is the name for the negative electrode

Answer 3

cathode (because it attracts the cations)

Question 4

what is a binary ionic compound

Answer 4

a compound consisting of just two elements

Question 5

how do you make an ionic compound molten

Answer 5

• by heating them beyond their melting point

Question 6

what can you observe during the electrolysis of lead (II) bromide

Answer 6

• bubbling at the anode as brown bromine gas is given off
• grey lead metal at the cathode

Question 7

what collects at the cathode in the electrolysis of aqueous solutions

Answer 7

• H+ ions and positive ions

Question 8

what collects at the anode in the electrolysis of aqueous solutions

Answer 8

• OH- ions and negative ions

Question 9

how can the electrolysis equipment be modified for the collection of gases

Answer 9

by using inverted test tubes over the electrodes

Question 10

how to predict the products of electrolysis in an aqueous solution

Answer 10

• cathode: the LESS reactive ion becomes an element (between the ion and H+)
• anode: always chlorine, bromine, or iodine if present, otherwise the OH- ions will form H2O and oxygen

Question 11

what is the half equation for when OH- ions react in electrolysis

Answer 11

4OH- -> O2 + 2H2O + 4e-

Question 12

what happens to the ions that did not react during electrolysis

Answer 12

they remain as a third product in the solution

Question 13

what can you observe during the electrolysis of aqueous sodium chloride

Answer 13

• bubbles of pale green chlorine gas
• bubbles of colourless hydrogen gas

Question 14

what can you observe during the electrolysis of aqueous copper sulfate

Answer 14

• bubbles of colourless oxygen gas
• a pink-orange solid of copper

Question 15

what can you observe during the electrolysis of dilute sulfuric acid

Answer 15

• bubbles of colourless oxygen gas (as sulfate is not a halide ion)
• colourless gas hydrogen

Question 16

describe an experiment to set up electrolysis for molten compounds

Answer 16

• add to a crucible and heat
• add two graphite rods and connect this to a battery pack

Question 17

describe an experiment to set up electrolysis for aqueous solutions

Answer 17

• add solution and electrodes
• invert two small test tubes to collect gaseous products
• connect to a battery pack and turn on

Question 18

uses of aluminium

Answer 18

• aeroplane bodies - high strength to weight ratio (low density)
• saucepans - goods conductor of heat
• overhead power cables - good conductor of electricity

Question 19

uses of copper

Answer 19

• electrical wires - malleable and good conductor of electricity
• water pipes - unreactive and malleable

Question 20

use of low carbon (mild) steel

Answer 20

car body panels and wires - soft and malleable

Question 21

use of high carbon steel

Answer 21

tools and chisels - hard

Question 22

uses of stainless steel

Answer 22

cutlery, sinks and chemical plants - strong and resistant to corrosion

Question 23

what are the makeups of the three different types of steel

Answer 23

iron alloyed with:

• low-carbon (mild) - 0.25%carbon
• high-carbon - 0.5-1.4% carbon
• stainless - 20% chromium and 10% nickel

Question 24

what is an alloy

Answer 24

a mixture of a metal and one or more elements

Question 25

what are the three ways that ethanol can be oxidised

Answer 25

• complete combustion
• reaction with oxygen in air (aerobic oxidation)
• heating with dilute potassium dichromate in dilute sulfuric acid

Question 26

what observations can you see during the complete combustion of ethanol

Answer 26

• burns readily with an almost invisible blue flame

Question 27

what is the equation for the microbial oxidation of ethanol

Answer 27

ethanol + oxygen -> ethanoic acid + water

Question 28

observations when treating ethanol with an oxidising agent during the oxidation of ethanol

Answer 28

• potassium dichromate turns from orange to green
• very slow reaction so mixture is heated to its boiling point for an hour and a condenser is placed above to prevent the liquids from escaping

Question 29

describe the reactions of aqueous solutions of carboxylic acids with metals and metal carbonates

Answer 29

they act exactly the same as acids

the salts formed by the reaction all end in - anoate

eg. magnesium + ethanoic acid -> magnesium ethanoate + hydrogen

Question 30

what is vinegar

Answer 30

an aqueous solution containing ethanoic acid

Question 31

what is the key difference between addition polymers and condensation polymers

Answer 31

• addition polymers form the polymer molecule only
• condensation polymers form the polymer molecule and one water molecule per linkage

Question 32

what is a diol

Answer 32

an alcohol with a functional group at either end

Question 33

during condensation polymerisation what substance loses what

Answer 33

• dicarboxylic acid loses -OH
• diol loses -H