Tests for Ions - Quantitive analysis Flashcards
how do you carry out the flame test
- clean wire loop
- dip into HCL
- dip into metal compound and put on blue part of bunsen burner
why the test for any ion must be unique
Two or more ions means the colours will mix, making identification erroneous
why shouldn’t u make bunsen burner too hot
Avoid letting the wire get so hot that it glows red otherwise this can be confused with a flame colour
what colour does lithium give off what colour does sodium give off what colour does potassium give off what colour does calcium give off what colour does copper give off
- red
- yellow
- lilac
- orange/red
- blue/green
how can you identify metal from aqueous solutions
- adding sodium hydroxide and identify colour of precipitate
what colour does aluminium give off what colour does calcium give off what colour does copper give off what colour does iron II give off what colour does iron III give off
- white but when redissolved w excess NAOH form colourless
- white
- blue
- green
- brown
how can you figure out if ammonia is present
- add sodium hydroxide and heat
- place red litmus paper if turn blue alkali so ammonia
- strong smell but toxic and irritant
what is the test for halide ions
- first add nitric acid to halide then silver nitrate
why should you add nitric acid before silver nitrate
to remove any carbonate ions which would produce a precipitate of silver nitrate confusing results.
cannot use hydrochloric acid as already adding to chloride
what colour is given off in
chloride
bromide
iodide
- white
- cream
- yellow
test for carbonate
Add dilute acid and test the gas released.
Effervescence should be seen and the gas produced is CO2 which forms a white precipitate of calcium carbonate when bubbled through limewater:
what is test for sulfate ions
dilute hydrochloric acid and add aqueous barium chloride.
A white precipitate of barium sulfate is formed
what are the advantages of instrumental
- Modern instruments are very sensitive and can work with very small sample sizes
- They are faster and easier to use
- They provide greater accuracy
what is flame photometry
- instrumental method which allows u to identify ions, measure intensity and wavelength which produce line spectrum and can be used to work out concentration on calibration curve
how is flame photometry better than flame tests
- works with mixtures as compare it to reference spectra