Chemical Analysis

Pure memory stuff

Testing for Oxygen

Relights a glowing splint

Carbon dioxide - gas test

Bubbles through limewater

( lime water turns cloudy )

Hydrogen - gas test

Lit splint makes a squeaky pop

Chlorine

Bleaches damp blue litimus paper

Blue to white

Lithium - flame test

Crimson

Sodium - flame test

Yellow

Potassium- flame test

Lilac

Calcium - flame test

Orange - red

Testing for Magnesium

Add NaOH

white precipitate

Testing for Aluminium

Add NaOH

White precipitate

Magnesium VS Aluminium

Aluminium redissolves in excess NaOH

Testing for copper

Flame = green

OR

Add NaOH - blue ppt

Testing for Fe²⁺

Add NaOH

Green ppt

Testing for Fe³⁺

Add NaOH

Brown ppt.

Finding group 7 ions

Add Ag(NO₃)_aq. (+HNO₃)

Cl^-

white ppt

Br^-

Cream ppt

I^-

yellow ppt.

why add nitric acid when checking for group 7 ions

to remove carbonate impurities as they would give a false positive result.

testing for Sulphate ions - SO^2-₄

add barium chloride and hydrochloric acid

Sulphate = insoluble in solution = white ppt.

Testing for Carbonates - CO^2-₃

add acid

Test bubbles of gas w/ lime water

Lime water = cloudy.

how to test for metals

Flame test

Flame emission spectroscopy

chromatography - RP

• draw a pencil line

• Put a dot of black ink on the pencil line

• Place the chromatography paper in the solvent

• Leave to run

  Mark the position of solvent fronts

• Measure the distance that is travelled by ink

  ( using ruler )

• Measure the distance that is travelled by solvent fronts by the different dots

• Determine R_f value distance travelled by ink ÷ distance travelled by the solvent front

• Calculate R_f values of all dots

• Compare w/ known R_{f values}

Main problems w/ chromatography (3)

• start line in ink - ink runs up the paper

• Solvent above the start line - ink washes off the paper

• Wrong solvent used - ink must be insoluble.

R_f

Retention factor

Some inks have a greater force of attraction to the stationary phase, and so don't move up the paper as much.