12) Experimental techniques and chemical analysis

Define solvent

A substance that dissolves a solute

Define solute

A substance that is dissolved in a solvent

define Saturated solution

A solution containing the maximum concentration of a solute dissolved in the solvent at a specified temperature.

define residue

A substance that remains after evaporation, distillation, filtration or any similar process.

Define filtrate

A liquid or solution that has passed through a filter.

Test for Carbonate anions, CO₃^2-

Test: Add dilute acid to sample

Observation: Bubbles/fizzing/effervescence

Pass gas through limewater, it will turn milky if carbon dioxide is present, meaning the sample contains carbonate ions.

Test for Chloride, Cl^-, Bromide, Br^-, and Iodide, I^-.

Test:

Add/acidify with dilute nitric acid

Then add aqueous silver nitrate

Observation:

If Chloride present: White precipitate

If Bromide present: Cream precipitate

If Iodide present: Yellow Precipitate

Test for nitrate, NO₃^-

Test:

Add aqueous sodium hydroxide, then add aluminium foil.

Warm the mixture carefully

Observation:

Ammonia will be produced if present. Hold damp red litmus paper near the gas; it will turn blue.

Test for sulfate, SO₄^2-

Test:

Acidify with dilute nitric acid.

Then add barium nitrate

Observation:

White precipitate

Test for Sulfite, SO₃^2-

Test:

Add a small volume of acidified aqueous potassium manganate (VII)

Observation:

Acidified aqueous potassium manganate (VII) decolourises; purple to colourless.