C12 Chemical Analysis Flashcards
positive test for hydrogen
lighted splint into test tube ‘pops’
positive test for oxygen
glowing splint relights
positive test for carbon dioxide
turns limewater cloudy
positive test for chlorine
turns damp blue litmus paper white
positive test for water
cobalt chloride paper changes from blue to pink
or
white anhydrous copper sulfate changes from white to blue
what are flame tests for?
to identify the metal ion (cation) by the colour of its flame.
flame colour tests
lithium: crimson
sodium: yellow
potassium: lilac
calcium: orange-red
copper: green
describe the steps of a flame test
- dip into hydrochloric acid and high temperature to clean the loop,
- dip loop into metal compound being tested,
- hold it in blue flames,
- use the colour the flames turn to to identify what is the metal compound
describe the steps of a flame test
- dip into hydrochloric acid and high temperature to clean the loop,
- dip loop into metal compound being tested,
- hold it in blue flames,
- use the colour the flames turn to to identify what is the metal compound
ions that form white precipitates with sodium hydroxide solution
calcium
and magnesium ions
which metal ions form which-coloured precipitates in sodium hydroxide solution
copper II ions form blue precipitate
iron II ions form green precipitate
iron III ions form brown
3 negative ions you can perform chemical tests for
sulfates
carbonates
halides (group 7)
how to test for carbonates
add dilute acid: if it produces carbon dioxide effervescence (checked with limewater), it is a carbonate
how to test for halides
- add dilute nitric acid,
- add silver nitrate solution,
- if precipitate forms, halide ions are present and can be identified by the colour of the precipitate.
precipitate colours for halide ions when added to dilute nitric acid and silver nitrate solution
iodide: yellow
bromide: cream
chloride: white