chemical anaylsis Flashcards
what is a pure substance
a single element or compound not mixed with any other substances
how to test for a pure substance?
2
- measure melting and boiling points and compare against known data of its pure substance
- chromotography - pure substance will produce one dot
what is a formulation
and give examples
a mixture that has been designed as useful product
- paint, medicine, fertilisers alloys
how are formulations made
mix components in carefully measured quanties to ensure product has required properties
test for hydrogen?
positive result?
lit splint at open end of test tube
squeaky pop noise
test of oxygen?
positive result?
glowing splint in test tube
relights
glOwing Oxygen
test for carbon dioxide
postive result?
bubble gas through limewater
turns cloudy
test for chlorine
postive result?
damb blue litmus paper
turns red than bleached white
how do you do a flame test to test for metal ions?
dip inoculating loop (non-reactive metal) into dilute acid to clean
then dip in metal ion sample and place in edge of blue flame
dilute acid- to prevent contamination
flame colours of:
- Lithium
- Sodium
- Potassium
- Calcium
- Copper
- lithium- crimson
- sodium- yellow
- potassium- lilac
- calcium- orange-red
- copper- green
HAVE TO BE SPECIFIC!
cimium, sodilow, potasiliac, calcor, coppeen
process of flame emission spectroscopy
- metal ion into flame
- light from flame passed through spectroscope
- spectroscope converts light to line spectrum
- lines are specific for metal ion
how can you use the line spectrums from flame emission spectroscopy to know the concentration for metal
the more intense the lines are- the more concentrated
what metal ions react with sodium hydroxide to form white precipitates?
and how do you tell ONE of them apart from the rest?
- calcium
- magnesium
- aluminium- reacts with excess sodium hydroxide and dissolves
colour of preciptates formed by sodium hydroxide reacting with:
- Iron II?
- Iron III?
- Copper III?
and the formula
- Iron II- green precipitate- Fe(OH),2
- Iron III- brown precipitaes- Fe(OH),3
- Copper II- blue precipitates- Cu(OH),2
the NUMBER is alos the number used when balancing- NaOH, Na…
how do you test for a carbonate?
react with dilute acid
carbonates form CO2
CO2 can be identified by bubbling through limewater- and becomes cloudy
how to test for halide ions
react with dilute nitric acid
& dilute nitrate solution
forms silver halides
colour of precipitates of:
- silver chloride
- silver bromide
- silver iodide
- silver chloride- white
- silver bromide- cream
- silver iodide- yellow
how to test for sulfates
react with dilute acid
& barium chloride solution
to form white precipitates
what is chromatography used for?
to seperate mixtues and help identify substances
what is the mobie phase in chromatography
where molecules can move- the solvent
what is the stationary phase in chomatography?
where molecules cant move- the paper
if a substance in chromatography is more soluble- what will happen
they will spend more time in the mobile phase, meaning they will move faster and further
how to work out Rf value and why is it important
distance travelled by subtance/ distance travelled by solvent
different compounds have different Rf values
