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flame test for cations steps

• take a platinum wire loop and dip it in HCl and then rinse it in distilled water

• heat it over a Bunsen burner

• dip the wire in HCl again and the compound you want to test

• hold the wire loop in the blue part of the flame

• see what colour the flame turns

Lithium ions (Li⁺) burn with a

crimson / red  flame.

Sodium ions (Na⁺) burn with a

yellow flame

Potassium ions (K⁺) burn with a

 lilac flame.

Calcium ions (Ca²⁺) burn with an

orange-red flame.

Copper ions (Cu²⁺) burn with a

green flame.

what is the metal hydroxide test ?

add few drops of sodium hydroxide solution to the compound and if a hydroxide precipitate forms, the colour helps identify the metal ion in the compound

what colour precipitate do copper ions form

blue

what colour precipitate do calcium ions form

white

what colour precipitate do Fe 2+ ions form

green

what colour precipitate do Fe 3+ ions form

brown

what colour precipitate do aluminium ions form

white at first but if there‘s excess NaOH it forms a colourless solution

how to test for carbonate ions

react substance with dilute acids ( HCl ) , if it contains a carbonate ion , carbon dioxide will be produced

how to test for sulphate ions

acidify with HCl and add barium chloride. If white precipitate forms, sulphate ions are present

how to test for halide ions

acidify with nitric acid , add silver nitrate and watch the colour of the precipitate

when chloride ions react with silver nitrate they form a

white precipitate

when bromide ions react with silver nitrate they form a

cream precipitate

when iodide ions react with a silver nitrate they form a

yellow precipitate

test for ammonia gas

turns damp red litmus paper blue

advantages of instrumental method

more accurate / sensitive, faster , can test much smaller samples

disadvantages of instrumental method

expensive , complex, need to compare with known data

flame emission spectroscopy

put metal in flame and pass the light through a flame photometer and analyse line spectrum with known line spectrums to identify sample

what is true about each ion in a line spectrum

each metal ion has a unique line spectrum with different lines in different places

what does the intensity of the wavelength tell you in flame photometry

concentration of ion in solution

alkenes

unsaturated hydrocarbons which had at least one carbon-carbon double bond .

test for alkenes

alkenes turn bromine water colourless, alkanes see no colour change.

combustion of alkane or alkene

alkane/alkene + oxygen —> carbon dioxide + water

addition of hydrogen to alkene

alkene + hydrogen —> alkane

addition of halogen to alkene

alkene + halogen —> di-halo-alkane

alcohol functional group

OH

alcohol general formula

CnH(2n+1)OH

first 4 alcohols

methanol , ethanol , propanol , butanol

alcohol combustion word equation

alcohol + oxygen —> carbon dioxide + water

uses of alcohol

biofuels (ethanol/methanol) , as a solvent, as an alcoholic drink

oxidation of alcohols

alcohol + oxidising agent —> carboxylic acid + water

practical investigating the combustion of alcohols

pour 20cm³ of alcohol in an alcohol burner. Measure the mass of alcohol burner
Pour 100cm³ of water in a conical flask above the burner in a clamp
measure initial water temp and heat it until the temperature rises by approximately 40 degrees
find new mass of alcohol burner
find mass of alcohol burner to produce a 1 degree rise. compare results of other alcohols

fermentation reaction

glucose —> ethanol + carbon dioxide

fermentation method

mix yeast ( contains an enzyme ) with a solution of a carbohydrate . Keep the mixture between 30 and 40 degrees and in anaerobic conditions.

method to concentrate ethanol

ethanol has a lower BP than water. Heat solution to ethanol BP which separates it from the water by fractional distillation.

what happens when alcohols react with oxidising agents ?

the 2 hydrogens o the last carbon react with oxygen to form water and the oxygen and carbon form a double bond

reaction between metal carbonate and carboxylic acid

metal carbonate + carboxylic acid —> salt + water + carbon dioxide

carboxylic acid dissociation when it is dissolved in water ,word equation

carboxylic acid ←→ hydrogen ions + carboxylate ions

why are carboxylic acids weak acids

not all of the acid dissociated into ions which is why it is reversible

esterification reaction

diol + dicarboxyliuc acid --> ester + water

what is used to catalyse esterification

strong acid

carboxylic acid general formula

CnH2nO2

what is the functional group of carboxylic acid

COOH

first 4 carboxylic acids

methanoic acid, ethanoic acid, propanoic acid, butanoic acid

what happens in addition polymerisation

monomer double bond is broken to make polymer

how is addition polymerisation represented

n(monomer) → (polymer)n

condensation polymerisation definition

when a diol and dicarboxylic acid monomer react to make a polymer with ester functional group and water

what is the monomer with 2 alcohol functional groups called ?

Diol

What are the conditions needed for condensation polymerisation

2 different polymers with atleast 2 functional groups

What happens in condensation polymerisation ?

The Hydrogens from the diols reacts with the the OH from dicarboxylic monomer to form water . The oxygen bonds with carbon from the dicarboxylic acid to form a polymer with an ester functional group

What is a monomer with 2 carboxylic acid functional groups called ?

Dicarboxylic acid monomer

when do polyesters form

dicarboxylic acid and diol monomers react

what polymer is formed by the monomer nucleotide

dna

what polymer is formed by monomer amino acids

polypeptides / proteins

what polymer is formed by monomer sugar

starch and cellulose

polyethene properties and uses

flexible , durable and water proof. used for plastic bags and bottles

polypropene uses and properties

strong and resistant to fatigue so is used in containers

poly chloroethene uses and properties

rigid and durable. used for pipes

poly(tetrafluoroethene) uses and properties

non reactive and heat resistant . used for non-stick coatings and insulating electrical wires

Low Density Poly(ethene)

branches chains, molecules aren’t closely packed , flexible

High density Poly ethene

straighter chains, closely packed, harder

how to go from LDPE to HDPE

catalyst, higher temperature and pressure

thermosoftening polymers

melt when heated because there are weak intermolecular forces between chains making It easier to separate

thermosetting polymers

do not melt when heated because there are strong covalent bonds, called cross-links , between polymer chains. heat resistant

what are the 2 tests for cations

forming coloured precipitate with sodium hydroxide, flame tests

how to test for ammonium ions

add to sodium hydroxide. if ammonium ions present ammonia gas is given off

why add HCl to the solution when testing for sulphate ions

to remove any impurities , like carbonate ions, that could form a white precipitate and give false positive result

why do you add dilute nitric acid to the solution when testing for halide ions

to remove any impurities , like carbonate ions, that could form a pale precipitate and give false positive result

why do you add nitric acid instead of HCl when trying to purify the solution when testing for halide ions

you cant add HCl as you would add chloride ions and give a false result

test for carbon dioxide

when bubbled through lime water, it turns it cloudy/milky

what is measured in flame emission spectroscopy

light intensity and wavelength

what can be plotted when you have the light intensity of the flame of an ion and its concentration in solution

calibration curve

why are flame emission spectroscopy better than normal flame testing

it can test a mixture of ions , more accurate , faster

what is this:

line spectrum - made from flame spectrometry

how can you use line spectrum to identify ions presence

lines are in the same pattern / position

in metal ion flame tests , why is the wire dipped in HCl and then held in the flame

to clean the wire and prevent contamination of the sample

in metal ion flame tests, why is the wire dipped in HCl before dipping it in the metal compound

so the solid sticks on the wire and vaporises easier

what device creates line spectrum

flame photometer

why is it so important that in qualitative testing , the test for an ion is unique to that ion

so it only detects that specific ion , and there is no confusion with other ions

what are nanoparticles

small particles 1-100nm in size , contain roughly a few hundred atoms

what property of nanoparticles makes it so useful

high surface area to volume ratio

uses of nanoparticles

catalysts , medicine , electricity , sunscreens and lubricants, added to plastics in sport equipment

why are nanoparticles good as catalysts

high surface-area to volume ratio so more collisions and faster rate of reaction

what are 2 applications of nanoparticles in medicine

silver nanoparticles in polymer fibres used to make surgical masks and wound dressings , delivering medicine

why are silver nanoparticles added to surgical masks and wound dressings

they have antibacterial properties and give those properties to the fibres

why are nanoparticles used in medicine

tiny fullerenes can allow medicine to be absorbed more easily , delivers drugs to target areas more effectively

why are nanoparticle used in cosmetics such as sunscreen

blocks UV light and provides better protection and coverage , doesn’t leave any white marks

why are nanoparticles added to plastics in sport equipment

they make the plastic stronger and more durable without adding much mass

why are nanoparticles used in electrical circuits

nanotubes conduct electricity

why are nanoparticles used as lubricant coatings

improve thermal conductivity , better surface coverage due to surface area to volume ratio

disadvantages of nanoparticles

unknown side-effects or long-term impact on human health ,

may be toxic to cells and cause damage ,

harmful environmental impacts ,

some nanoparticles don’t breakdown easily and could build up

glass ceramics

transparent, strong , heat-insulating and durable

Glass uses

Windows and building materials as it’s more durable than other materials like plastic

2 types of glass ceramics

Soda-lime , borosilicate

Soda lime glass

Made by heating a mixture of limestone , sand and sodium carbonate until it melts . Then it cools to form glass

Borosilicate glass

Made by mixing sand and boron trioxide