Qualitative Analysis Flashcards
(31 cards)
What charge ions do flame tests test for?
Positive ions
Why can you use flame tests to identify the metal ion of a compound?
Metals burn with a characteristic colour and therefore goes a distinctive colour over a flame
Describe the lab method of a flame test.
Clean the nichrome wire with hydrochloric acid and hold in a blue flame.
Dip wire into solid sample
Hold over a blue flame
Determine colour and identify ions.
Colour of Li+ ions
Crimson
Colour of Na+ ions
Yellow
Colour of K+ ions
Lilac
Colour of Cu2+ ions
Blue/green
The colour of Ca2+ ions
Orange/red
What colour precipitate is formed when copper compounds react with NaOH
Blue precipitate
What colour precipitate is formed when Iron(II) compounds react with NaOH
A green precipitate
What colour precipitate is formed when iron(III) compounds react with NaOH
Brown precipitate
What colour precipitate is formed when magnesium compounds react with NaOh
White precipitate
What colour precipitate is formed when aluminium compounds react with NaOH
White precipitate that’s soluble in excess
What colour precipitate is formed when calcium compounds react with NaOH
White precipitate
How to test for carbonate ions
Add 3cm3 or dilute HCl to carbonate solid salt
Test gas with limewater -> cloudy if CO2
How to test for alkenes
Bromine water orange to colourless
Test for chlorine
Bleaches damp litmus paper white
Test for hydrogen
Burns with a squeaky pop
Test for oxygen
Relights a glowing splint
What compound do you use to detect halide ions?
Silver nitrate
Method for determining halide ions
Acidify salt with few drops of nitric acid then add drops of silver nitrate
What colour would a chloride precipitate turn with silver nitrate?
White precipitate (WC-bleach toilet, white chlorine)
What colour would bromide precipitate turn with silver nitrate?
Cream precipitate ( BC )
What colour would a iodide precipitate turn with silver nitrate?
yellow precipitate