Topic 4 - Cation Tests Flashcards
what colour flame does Li burn with?
red
what colour flame does Na burn with?
yellow
what colour flame does K burn with?
purple
what colour flame does Ca burn with?
orange-red
what colour flame does Cu burn with?
blue-green
What do flame tests identify?
metal ions (cations)
what is the precipitate colour of copper(II)?
blue
How do flame tests work?
compounds of some metals burn with a characteristic colour
How do precipitation reactions work?
A few drops of dilute sodium hydroxide solution are added at a time to the test solution. Different metal ions produce different coloured hydroxide precipitates.
what is the precipitate colour of iron(II)?
green
what is the precipitate colour of iron(III)?
reddish-brown
if there is no coloured precipitate what ion may be present?
ammonium ions
how do you check for ammonia gas?
use a damp piece of red litmus paper. if there is ammonia present the paper will turn blue
