Test for ions and radicals Flashcards
Thiosulphate: equation
S₂O₃2-
Thiosulphate: reagent
Add dilute HCl to get four products.
Thiosulphate: observations
- A yellow precipitate of sulphur forming.
- Sulfur dioxide gas given off = distinct smell as it is quite pungent.
- the ppt is sulphur (S)
Thiosulphate: How to identify sulphur dioxide gas
By putting a spot of potassium permanganate on filter paper and hold over reaction, purple colour disappears as sulphur dioxide acts as a reducing agent reducing Mn (+7) which is purple to Mn (+2) which is colourless.
Sulphate equation
SO₄2-
Sulphate reagent
Add barium chloride solution, a white ppt of barium sulfate is formed.
Sulfate - why is dilute HCl added?
To distinguish - no reaction (white ppt remains) as barium sulphate is insoluble in dilute acid.
Sulphite equation
SO₃2-
Sulphite reagent
Add barium chloride solution, a white ppt of barium sulfite is formed.
Sulphite - to distinguish between the two precipitates.
Add dilute HCl solution to distinguish, the ppt disappears and sulphur dioxide gas is given off if a sulfite ion is present.
Sulphite reaction - what happens if you add dilute HCl solution to the white ppt of barium sulfate?
The ppt remains as no reaction occurs.
Carbonate and hydrogen carbonate equations.
CO₃2- and HCO₃-
Carbonate and hydrogen carbonate reaction - reagent.
Add dilute acid
Carbonate and hydrogen carbonate: what happens when you add dilute acid and how do you know?
if a carbonate or hydrogen carbonate is present then carbon dioxide will be given off and can be noted by light effervescence
Carbonate and hydrogen carbonate: how to test for CO2 gass
bubble the carbon dioxide through a colourless solution of limewater. it turns milky white
what is limewater?
an aqueous solution of calcium hydroxide
to distinguish between a Carbonate and hydrogen carbonate: reagent
add magnesium sulfate to both
formula for magnesium sulfate
MgSO4
to distinguish between a Carbonate and hydrogen carbonate: if a carbonate is present
white ppt is produced - magnesium carbonate
to distinguish between a Carbonate and hydrogen carbonate: if a hydrogen carbonate is present and why
no ppt present as magnesium hydrogen carbonate is soluble in the solution
what happens if you boil magnesium hydrogen carbonate and why
you get a white ppt as hydrogen carbonates decompose on heating
Nitrate: reagents
freshly made Iron (II) sulphate solution
concentrated H2SO4
Nitrate: H2SO4
sulphuric acid
Nitrate: is there a ppt in aqueous nitrate solution and why
no because nitrate ion is soluble in water
Nitrate: what colour is the fresh Iron (II) sulphate solution
a greenish colour
Nitrate: how do you add the conc. H2SO4 soln.?
slowly ad carefully down the inside of the test tube
Nitrate: what falls to the bottom of the test tube?
the sulphuric acid
Nitrate: how do you confirm that it’s a nitrate
a brown ring forms at the junction of the substances
Nitrate: formula for the substance that is the brown ring
FeSO4.NO
Nitrate: formula for nitrate ion
NO3-
chloride: ion
Cl-
chloride: reagents
silver nitrate solution and concentrated nitric acid
chloride: confirmation
immediate white ppt forms
chloride: why is the reaction immediate
it is an ionic reaction
chloride: what does the immediate formation of the white ppt tell us?
that there are chloride ions present in the aqueous soln. tested
phosphate: ion
PO4 3-
phosphate: reagents
ammonium molybdate and 5 drops of conc. nitric acid
phosphate: what condition is needed?
heat gently