Chem

Question 1

Testing for gases

Answer 1

Hydrogen-place a burning splint into a tube containing gas . Pop sound will occur if hydrogen is present

Oxygen-place glowing splint into gas. If it is oxygen the splint will relight

Carbon dioxide-lime water turns cloudy

Chlorine gas-red litmus paper goes white

Question 2

Flame colours

Answer 2

Lithium-crimson 
Potassium-lilac
Copper-green
Calcium-orange 
Sodium-yellow

Question 3

Problems with flame test

Answer 3

If chemical is low in concentration then the flame is hard to distinguish

Sample could contain a mix which would mask the colour

Question 4

Flame emission spectroscopy

Answer 4

Place metal solution into flame
Light emitted is passed into a spectroscope
This machine converts light into a line on a spectrum
Position of line allows us to identify the metal

Question 5

Pros of instrumental methods

Answer 5

Much quicker
Much more sensitive
These methods are more accurate

Question 6

Metal hydroxide percipatates

Answer 6

If you react magnesium or aluminum or calcium with sodium hydroxide then the precipitate is white.

Copper2 forms a blue precipitate
Iron 2 forms a green precipitate
Iron3 forms a brown precipitate

Question 7

Identifying non metal ions

Answer 7

Carbonate - add dilute acid . If present fizzing will occur and a gas is formed . Funnel gas into lime water . If it goes cloudy then the gas was carbon dioxide

Sulfate-add dilute HCL to sample , add barium chloride to sample .white precipitate forms .

Halide-add dilute nitric acid , add dilute silver nitrate , each halide will form a different colour

Chloride-white
Bromide-cream
Iodide-yellow

Question 8

Modern atmosphere composition

Answer 8

78 percent nitrogen

21 percent oxygen

Question 9

Early atmosphere

Answer 9

During the first billion years it is is believe that there were intense waves of volcanic activity which released lots of water vapour. This water formed the oceans

Volcanoes also released lots of carbon dioxide . The atmosphere at this point was primarily all carbon dioxide, little to no oxygen was present

Question 10

How did atmosphere change ?

Answer 10

Carbon dissolved into water slowly forming carbonate rock on sea beds. This absorbed lots from the atmosphere

Photosynthetic algae developed the ability to photosynthesise replacing huge amounts of carbon dioxide with oxygen

Question 11

Formation of fossil fuels

Answer 11

Coal-formed by the remains of plant life . If the die in wet marshlands decomposition will not occur due to a lack oxygen. Over time these remains are compacted and compressed under high pressure and temp forming coal

Crude oil-formed from plankton. When the do not decompose they are compressed and subjected to high temperatures forming oil

Natural gas-found near pockets of oil

Question 12

What is the general formula of alkanes

Answer 12

CnH2n+2

Question 13

Properties of hydrocarbons

Answer 13

Viscosity-As the size of the hydrocarbons increase so does their viscosity

Flammability-short chain hydrocarbons are much more flammable

Boiling point-short chain hydrocarbons have a lower boiling point

Question 14

Fractional distillation process

Answer 14

Crude oil is heated to a very high temperature
The oil boils and vapour is fed into the column
The vapours rise , the different hydrocarbons condense at different temperatures in the fractionating column.
Very long hydrocarbons condense at the bottom

Question 15

Cracking

Answer 15

Long chained hydrocarbons are not as useful as smaller chained hydrocarbons

So they are separated into smaller hydrocarbons this is done through breaking the bonds between the atoms using high temperatures

However by separating the hydrocarbons alkenes are formed

Question 16

What is an alkene ?

Answer 16

Unlike alkanes , alkenes are unsaturated hydrocarbons. They have double bonds between 2 carbon atoms and have 2 less hydrocarbons than the alkanes of the same name

To test for alkenes use bromine water,it will turn from orange to colourless

Question 17

General formula for alkenes

Answer 17

CnH2n

Question 18

What the is the functional group of alkenes

Answer 18

The double bond between 2 carbon atoms

Members of a homologous series all have the same functional group

Question 19

Hydrogenation

Answer 19

When an alkenes reacts with hydrogen to form the alkane of the same name

A nickel catalyst is needed
Double bond converts into 2 single bonds

Question 20

Hydration

Answer 20

Reacting alkenes with water forms an alcohol
The double bond is broken
Pressure 70 atm
Temp at 300
Phosphoric acid as a catalyst

Question 21

Reacting with halogens

Answer 21

Reacting halogens with alkenes causes the alkene to break it’s double bond . The 2 bonds connect to the 2 halogen atoms

Question 22

What produces ethanol

Answer 22

Hydration with ethene

Fermentation of sugar in anaerobic conditions causes ethanol to form

Question 23

Reacting alcohol with oxidising agent

Answer 23

Forms a carboxylic acid with a functional group of cooh

Question 24

What happens when you place a carboxylic acid in water

Answer 24

Does not fully dissociate

CH3COO-
H2+

Both ions

Question 25

What is an ester

Answer 25

When an alcohol and carboxylic acid reacts the ester is formed.

Remember that the hydrogen from the hydroxide is lost from both sides

Question 26

What is a polymer

Answer 26

Long chained molecules made from smaller identical molecules called monomers.

Question 27

When drawing a poly(alkene)

Answer 27

Remember to break double bond
The new bonds overlap the brackets you have placed on either side
Place a small n next to the bracket

Question 28

What is polytetrafluoroethene used for

Answer 28

Teflon

Question 29

What is poly(methyl2-cyanpropenoate) used for

Answer 29

Super glue

Question 30

What is poly(methyl2-propenoate)used for

Answer 30

Perspex

Question 31

Concentrations

Reversible reactions

Answer 31

If we increase the reactants then the product yield will increase to oppose change

If we decrease products then more reactants will be made so that more products can be produced

Question 32

Temperatures and reversible reactions

Answer 32

If forward reaction is exothermic

Temperature increase will cause equilibrium to shift to endothermic side which is reactant side increasing reactants

I

Question 33

Pressure and equilibrium

Answer 33

When the pressure is increased the equilibrium will shift to the side that has less gas molecules

Question 34

Potable water

Answer 34

Contains dissolved substances. It is not pure but safe to drink.

Question 35

Waste water treatment

Answer 35

Sewage is passed through mesh removing large solids
Sewage settles in tanks producing a sludge that sinks. The sludge is removed

Air is bubbled through the sewage allowing bacteria to multiply and digest any organic materials remaining

Question 36

Phytomining

Answer 36

Grow plants on land containing the metal compound
These plants absorb the metal and transfers it into their tissue
These plants are burnt . Their ash containing the metal compound

Question 37

Bioleaching

Answer 37

Bacteria are mixed with low grade ore . They react and produce a solution called leachate which contains the metal

Question 38

Reacting alcohols

Answer 38

Oxygen-burns well .
Sodium-fizz
Water-neutral solution

Question 39

Thermosetting

Answer 39

Polymers that do not melt when exposed to heat as they have covalent bonds linking different chains together

Question 40

Thermosoftening

Answer 40

These polymers melt when exposed to heat as there are no bonds between chains

Question 41

Addition polymers

Answer 41

Formation of polymers form lots of small molecules that all join together,no other product is formed

Question 42

Condensation

Answer 42

When these polymers form other products such as water are produced