chemical tests

test for hydrogen and positive result

a lit splint produces a squeaky pop

test for oxygen and positive result

a glowing splint relights

test for carbon dioxide and positive result

bubble the gas through limewater; limewater goes cloudy/white precipitate forms

test for ammonia and positive result

damp red litmus paper turns blue

test for chlorine and positive result

damp blue litmus paper turns red then white

describe how to carry out a flame test

cleanse a nichrome wire in hydrochloric acid to remove any oxidation, place into a hot bunsen flame until no colour is shown

take a sample of the metal on a wire and put it in a flame which will turn a specific colour

what is the flame test mainly used for?

cations

flame test colour for lithium ions

red

flame test colour for sodium ions

orange

flame test colour for potassium ions

lilac

flame test colour for calcium ions

orange-red

flame test colour for copper (II) ions

blue-green

test for ammonium (cation)

add sodium hydroxide solution, and warm it, which will cause ammonia gas to be produced - damp red litmus paper will then turn blue

test for copper (II) ions

add to sodium hydroxide solution, blue precipitate formsa

test for iron (II) ions

add to sodium hydroxide solution, green precipitate forms

test for iron (III) ions

add to sodium hydroxide solution, brown precipitate forms

which anions do we test for

halide

sulphate

carbonate

test for halide ions

add dilute nitric acid then silver nitrate solution

positive result for chloride

white precipitate

positive result for bromide

cream precipitate

positive result for iodide

yellow precipitate

describe the test and positive result for sulfate ions

add hydrochloric acid to acidify the solution removing any carbonate, then add barium chloride solution

a white precipitate will form

describe the test for carbonate ions and the positive result

add a dilute acid which will form carbon dioxide gas then perform the carbon dioxide test to identify it

describe the chemical test for the presence of water

anhydrous copper (II) sulfate turns blue in the presence of water (from white)

describe the physical test for purity of water

water will boil at exactly 100*C - impure water will boil at a range of temperatures