chemistry practical

Al³⁺ + NaOH(aq)

White ppt, soluble in excess (colourless solution)

Al³⁺ + NH₃(aq)

White ppt, insoluble in excess

NH₄⁺ + NaOH(aq)

No ppt; ammonia gas produced on warming

Ba²⁺ + NaOH(aq)

Faint white ppt (unless [Ba²⁺] very low)

Ba²⁺ + NH₃(aq)

No ppt

Ca²⁺ + NaOH(aq)

White ppt (unless [Ca²⁺] very low)

Ca²⁺ + NH₃(aq)

No ppt

Cr³⁺ + NaOH(aq)

Grey-green ppt, soluble in excess giving dark green solution

Cr³⁺ + NH₃(aq)

Grey-green ppt, insoluble in excess

Cu²⁺ + NaOH(aq)

Pale blue ppt, insoluble in excess

Cu²⁺ + NH₃(aq)

Pale blue ppt, soluble in excess giving dark blue solution

Fe²⁺ + NaOH(aq)

Green ppt turning brown on contact with air, insoluble in excess

Fe²⁺ + NH₃(aq)

Green ppt turning brown on contact with air, insoluble in excess

Fe³⁺ + NaOH(aq)

Red-brown ppt, insoluble in excess

Fe³⁺ + NH₃(aq)

Red-brown ppt, insoluble in excess

Mg²⁺ + NaOH(aq)

White ppt, insoluble in excess

Mg²⁺ + NH₃(aq)

White ppt, insoluble in excess

Mn²⁺ + NaOH(aq)

Off-white ppt rapidly turning brown on contact with air, insoluble in excess

Mn²⁺ + NH₃(aq)

Off-white ppt rapidly turning brown on contact with air, insoluble in excess

Zn²⁺ + NaOH(aq)

White ppt, soluble in excess

Zn²⁺ + NH₃(aq)

White ppt, soluble in excess

Carbonate, CO₃²⁻ test

CO₂ gas liberated by dilute acids

Chloride, Cl⁻ test

White ppt with Ag⁺(aq), soluble in NH₃(aq)

Bromide, Br⁻ test

Cream/off-white ppt with Ag⁺(aq), partially soluble in NH₃(aq)

Iodide, I⁻ test

Pale yellow ppt with Ag⁺(aq), insoluble in NH₃(aq)

Nitrate, NO₃⁻ test

NH₃ liberated on heating with OH⁻(aq) and Al foil

Nitrite, NO₂⁻ test

NH₃ liberated on heating with OH⁻(aq) and Al foil; decolourises acidified aqueous KMnO₄

Sulfate, SO₄²⁻ test

White ppt with Ba²⁺(aq), insoluble in excess dilute strong acids

Sulfite, SO₃²⁻ test

White ppt with Ba²⁺(aq), soluble in excess dilute strong acids; decolourises acidified aqueous KMnO₄

Thiosulfate, S₂O₃²⁻ test

Off-white/pale yellow ppt slowly forms with H⁺

Test for ammonia, NH₃

Turns damp red litmus paper blue

Test for carbon dioxide, CO₂

Gives a white ppt with limewater

Test for hydrogen, H₂

'Pops' with a lighted splint

Test for oxygen, O₂

Relights a glowing splint

Test for iodine, I₂

Gives blue-black colour with starch solution

Fehling's reagent positive test

Orange/red ppt — indicates aldehyde functional group

Tollens' reagent positive test

Silver mirror/black ppt — indicates aldehyde functional group

Alkaline aqueous iodine positive test

Yellow ppt — indicates CH₃CO– or CH₃CH(OH)– group

Acidified KMnO₄ positive test

Colour changes purple to colourless — indicates a compound that can be oxidised