Qualitative Analysis Flashcards
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
How do you identify sulphate ions SO4^2-
Acidly with a few drops HCl then add barium chloride = white precipitate
How do you determine anions?
Using precipitation reaction
What colour do sulphate ion precipitate go with barium chloride?
White precipitate
What is Flame emission spectroscopy?
Measure of wavelength of light in a flame to identify all of the ions in that mixture
In flame emission spectroscopy how do you find concentration of ions?
Measure the light intensity of the flame with that wavelength for the ion
Advantages of flame spectroscopy machine
Very quick and accurate, can find more data as it is density e
DisAdvantages of flame spectroscopy machine
Expensive, need training to understand, complex data findings
