revision

Question 1

Test for alkenes (double carbon bond)

Answer 1

alkene + orange bromine water turns colourless when shaken

addition reaction because double carbon bonds are split and bromine is added to each (dibromoethane)

Question 2

Test for alkanes

Answer 2

alkane + halogen + UV light 
make haloalkane (bromomethane)

Question 3

rust

Answer 3

iron + oxygen + water = hydrated iron (III) oxide

soft and crumbly so flakes off to allow more to rust

Question 4

barrier methods (rust)

Answer 4

SACRIFICIAL placing a more reactive iron to react instead of iron ( eg. forming zinc oxide)

GALVANISING sprayed coating of zinc
PAINTING / PLASTIC
OILING - moving parts (bike chains)

Question 5

extracting iron raw materials

Answer 5

haematite - iron ore (Fe2O3)
coke - almost pure carbon
limestone - used to remove impurities
Found in Australia and canada

Question 6

extracting iron method (blast furnace)

Answer 6

C + O2 = CO2 coke burns in oxygen to produce carbon dioxide (at 1500 C)
CO2 + C = 2CO
3CO + FeO3 = 3CO2 + 2FE carbon monoxide reduces iron ore to iron (molten and dense) where it is tapped off.

Question 7

extracting iron removing impurities

Answer 7

main impurity is sand (SiO2) - removed using limestone
CaCO3 = CaO + CO2
CaO + SiO2 = CaSi3 calcium oxide reacts with silicon oxide to form calcium silicate (slag)
Can be used for road building and fertiliser

Question 8

Iron (II) test

Answer 8

add sodium hydroxide and turns sludgy green

Question 9

Iron (III) test

Answer 9

add sodium hydroxide and turns reddish brown

Question 10

Sulfates test

Answer 10

Dilute HCl and barium chloride makes white precipitate
(HCl makes sure there are not any traces of carbonate or sulphite ions, which form precipitates and would confuse results)

Question 11

ammonia gas (NH3) test

Answer 11

turns damp red litmus paper blue
strong smell (can be harmful to eyes)

Question 12

ammonium ions (NH4) test

Answer 12

sodium hydroxide and ammonia gas given off (check litmus paper)

Question 13

copper (II) test

Answer 13

sodium hydroxide forms blue precipitate

Question 14

methyl orange

Answer 14

acid - red

alkaline - yellow

Question 15

simple molecular substances (covalent)

Answer 15

• atoms within molecule are held together using very strong covalent bonds, however between molecules (intermolecular) are very weak
• makes melting and boiling points very weak
• often gases or liquid at room temperature

Question 16

giant covalent structures

Answer 16

similar to giant ionic structures (but no charged particles)

• all atoms are bonded together by strong covalent bonds and it takes a lot of energy to break them so have high melting and boiling points
• don’t conduct electricity (not even molten) except graphite

Question 17

Methylbenzene

Answer 17

HCl does not dissociate in methylbenzene into ions, there are no H+ ions so it’s not acidic
HCl in methylbenzene with blue litmus paper stays blue
If there is moisture it turns red

Question 18

Haber process conditions

Answer 18

200atm
iron catalyst
450C

Question 19

Cracking hydrocarbons conditions

Answer 19

powdered catalyst of silica or alumina

600 - 700C

Question 20

filtration

Answer 20

used to separate an insoluble substance from a liquid

can be used to filter impurities

Question 21

crystallisation

Answer 21

separates a soluble solid from a solution
heat solution ( some of solvent will evaporate and stop heating when crystals form)
evaporate and dry product ( using drying oven or desiccator) contains chemicals that remove water from surroundings

Question 22

water of crystallisation

Answer 22

solid salts consist of a lattice of positive and negative ions.
water in a lattice is called water of crystallisation
water molecules contain a small positive charge (from h+ ions) and a small negative charge (on oxygen atoms)
they are attracted to the ions in the lattice and make the salt hydrated