sc25, quantative analysis: tests for ions (paper 2) Flashcards
what is the flame test
test for metal ions
what happens during the flame test
dip the clean loop in a solution of the ions and hold at the edge of a blue flame, which will change colour
what’s a precaution you should take during the flame test
- clean the flame test loop in acid each time
- rinse with water
- check it’s clean with the flame
what colour is lithium in the flame test
red
what colour is sodium in the flame test
yellow
what colour is potassium in the flame test
lilac
what colour is calcium in the flame test
orange-red
what colour is copper in the flame test
blue-green
what happens during the hydroxide test
the sample solution is placed in a test tube and a few drops of dilute sodium hydroxide solution are added
what colour is copper in the hydroxide test
blue
what colour is iron (II) in the hydroxide test
green
what colour is iron (III) in the hydroxide test
brown
how do you test for sulfate ions
- add dilute hydrochloric acid then barium chloride solution
- white precipitate of barium sulfate forms
how do you test for carbonate ions
- add acid
- bubbles of carbon dioxide forms
how to test for chloride ions
- add dilute nitric acid then silver nitrate solution
- white precipitate
how to test for bromide ions
- add dilute nitric acid then silver nitrate solution
- cream precipitate
how to test for iodide ions
- add dilute nitric acid then silver nitrate solution
- yellow precipitate
how to test for ammonium ions
- add sodium hydroxide solution
- heat it
- ammonia is produced
how do you test for ammonia gas
- the reaction produces water + ammonia
- test for the gas by:
- damp red litmus paper turning blue
- hydrogen chloride gas (from concentrated hydrochloric acid) reacts with ammonia to form ammonium chloride
describe what instrumental methods of analysis does
use machines to detect and analyse substances
what are the three improved things intrumental methods offer over simple chemical tests
- sensitivity
- accuracy
- speed
how is sensitivity improved in instrumental methods than chemical methods
they can detect and analyse very small amounts of different substances
how is accuracy improved in instrumental methods than chemical methods
they can measure amounts of different substances very accurately
how is speed improved in instrumental methods than chemical methods
they carry out each analysis quickly, and the machine can run all the time
what can the data from a flame photometer tell us
- identify the metal ions present in the sample by comparing the spectrum with a reference spectrum from a known substance
- determine the concentration of ions in a solution using a calibration curve
