Topic 9 Flashcards
what do you use the flame test to identify
metal ions
what colour do the metal ions go in the flame test
lithium - red sodium - yellow potassium - lilac calcium - red-orange copper - blue-green
how do you carry out flame test
clean a nichrome wire loop by dipping it into hydrochloric acid and rinsing it in distilled water
dip wire loop into metal compound and put in clear blue part of flame
what is the test for metal hydroxides other than flame
add sodium hydroxide to metal compound and a precipitate will form because some metal hydroxides are insoluble aluminium - white colourless in excess calcium white copper blue iron 2 green iron 3 brown
what is the test for ammonia
add sodium hydroxide
gently heat
damp red litmus blue
what is the test for halide ions
dliute nitric acid and silver nitrate
chlorine white
bromine cream
iodine yellow
nitric acid added first to get rid of any carbonate ions - they produce a pale precipitate with silver nitrate too which would confuse the results
you cant use HCl because you would be adding chloride ions
what is the test for carbonates
add dilute hydrochloric acid
mixture fizz because carbonate react with acid to form CO2
gas produced bubble through lime water and turn cloudy
what is the test for sulfate ions
add dilute HCl to stop ant precipitate reactions not involving sulfate ions from taking place and barium chloride
white precipitate will form of barium sulfate
what is flame photometry
- accurately identify different metal ions in a solution and their concentration
- instrumental method allowing you to identify ions in a solution
- each ion produces a unique line spectrum
- the intensity of the measured wavelength indicated the concentration of that ion in solution
- work out conc from a calibration curve
- it can be used to identify different ions in mixtures making it more useful than flame tests which only work for substances that contain a single metal ion
what are the advantages of using instrumental analysis like flame photometry
- very sensitive and can detect even the tiniest amounts of substances
- n very fast and tests can be automated
- very accurate as it removes human error
what are alkanes
- homologous series of hydrocarbons
- formula CnH2n+2
- saturates
- orange in bromine water
what are alkenes
- homologus series of hydrocarbons with one C=C functional group
- formula CnH2n
- unsaturated as can make more bonds as the double bond can open up
- colourless in bromine water as addition reaction takes place where bromine is added across the alkene double bond
what happens to hydrocarbons in combustion reactions
- they are oxidised
- alkanes and alkenes burn in oxygen in combustion reactions
- during complete combustion they’re oxidised to form carbon dioxide and water
ethane + oxygen -> carbon dioxide and water
ethene + oxygen -> carbon dioxide and water
what is addition polymerisation
- polymers are substances of high average relative molecular mass made by joining small repeating units called monomers together
- the monomers that make up addition polymers have a double covalent bond
- lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains. this is called addition polymerisation
what are the uses of polymers
poly(ethene):
plastic bags, bottles, wire insulation
poly(propene):
crates, garden furniture, ropes
poly(chloroethene) (PVC):
window frames and water pipes
poly(tetrafluroethene) (PTFE):
nonstick pans and waterproof clothing
why are the properties of polymers
poly(ethene)
flexible, cheap, electrical insulator
poly(propene)
flexible, strong, trough and mouldable
poly(chloroethene)
tough and cheap
poly(tetrofluroethene)
unreactive, tough and nonstick
what is condensation polymerisation
- usually involves two different types of monomer
- the monomers react together and bonds form between them making polymer chains
- each monomer has at least two functional groups one on each end of the molecule
- each functional group can react with the functional group of another monomer creating a long chain of alternating monomers
- for each new bond that forms a small molecule (water) is lost