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Specification

a) Recognise the results of reactions of compounds specifically mentioned in Units 1 and 2 of the

specification and the results of tests for simple ions: carbonate, hydrogencarbonate, sulphate(VI),

sulphite, chloride, bromide, iodide, nitrate, ammonium, lithium, sodium, potassium, magnesium,

calcium, strontium and barium

Tests

Ion Formula Test Observations

Carbonate CO32-

Test 1Heat the solid in a test tube with a Bunsenburner.

It should decompose producing the oxideand carbon dioxide. E.g.

Test for the gas using limewater solution.

Limewater should turnfrom colourless tocloudy in the

presence of carbondioxide due toprecipitation ofcalcium carbonate.

Test 2Add dilute HCl to the solid.Test for the gas evolved using limewatersolution.

Vigorouseffervescence.Limewater should turnfrom colourless tocloudy in the

presence of carbondioxide due toprecipitation of

calcium carbonate.

Hydrogencarbonate HCO3-

TestAdd calcium chloride to ahydrogencarbonate solution.

No precipitate formssince calciumhydrogencarbonate issoluble.

Sulphate (VI) SO42-

TestAdd barium chloride solution acidified withdilute HCl to the test solution.

White precipitate ofbarium sulphateforms.

Sulphite SO32-

TestWarm the sulphite with dilute HCl.

Test for gases using acidified potassiumdichromate(VI) solution (or paper)

The solution turns

green.

Chloride Cl-

Test 1Add concentrated sulphuric acid to thesolid chloride.

White steamy acidicfumes are seen - HClfumes.

Test 2Add dilute nitric acid to a solution of achloride to acidify the solution. Thiseliminates any carbonates or sulphites.

White precipitate ofAgCl forms.

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Add silver chloride to the solution.Add dilute ammonia solution. Solid dissolves.

Bromide Br-

Test 1Add concentrated sulphuric acid to thesolid bromide.

Steamy brownishacidic fumes are seen.

Test 2'Add dilute nitric acid to a solution of abromide to acidify the solution. Thiseliminates any carbonates or sulphites.Add silver nitrate to the solution.Add concentrated ammonia solution.

Cream precipitate ofAgBr forms.

Solid dissolves.

Iodide I-

Test 1Add concentrated sulphuric acid to thesolid iodide.

Purple acidic fumesare seen. The mixtureturns to a brownslurry.

Test 2Add dilute nitric acid to a solution of a

iodide to acidify the solution. Thiseliminates any carbonates or sulphites.

Add silver nitrate to the solution.

Add concentrated ammonia solution.

Yellow precipitate ofAgI forms.

Solid is insoluble.

Nitrate NO3-

Test 1Heat solid nitrate.

If group 1 solid (not Li) then willdecompose to give the nitrite and oxygen.

All other solid nitrates decompose to givethe metal oxide, nitrogen dioxide andoxygen.

Oxygen gas is evolvedthat will relight aglowing splint.

Brown gas is seen(NO2). Oxygen gas isalso evolved and willrelight a glowingsplint.

Test 2Boil nitrate solution withaluminium/Devardas alloy, in sodium

hydroxide solution.Test vapour with red litmus paper.

Litmus paper turnsblue in the presence

of ammonia.

Ammonium NH4+

TestWarm ammonium compound withNaOH.Test vapours immediately using damp

red litmus paper.

NH3turns the litmus paperblue.

Lithium Li+

TestDip nichrome wire in HCl.

Dip wire in solid.

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Heat wire in centre of flame.

Observe colour of flame.

A carmine red flameis seen.

Sodium Na+

TestDip nichrome wire in HCl.

Dip wire in solid.

Heat wire in centre of flame.

Observe colour of flame.

A yellow flame isseen.

Potassium K+

TestDip nichrome wire in HCl.

Dip wire in solid.

Heat wire in centre of flame.

Observe colour of flame.

A lilac flame is seen.

Magnesium Mg2+TestAdd NaOH solution to the magnesium

solid.

A white solid formswhich is insoluble inexcess NaOH(aq).This is Mg(OH)2(s)

Calcium Ca2+

TestDip nichrome wire in HCl.

Dip wire in solid.

Heat wire in centre of flame.

Observe colour of flame.

A brick red flame isseen.

Strontium Sr2+

TestDip nichrome wire in HCl.

Dip wire in solid.

Heat wire in centre of flame.

Observe colour of flame.

A crimson red flame isseen.

Barium Ba2+

TestDip nichrome wire in HCl.

Dip wire in solid.

Heat wire in centre of flame.

Observe colour of flame.

A apple green flame isseen.