Chemical Tests

These flashcards cover the chemical tests for gases, cations, anions, and the tests for water purity as outlined in the Edexcel IGCSE Chemistry notes.

What is the test for hydrogen gas?

Use a burning splint held at the open end of a test tube of the gas, which creates a ‘squeaky pop’ sound.

How do you test for oxygen gas?

Insert a glowing splint into a test tube of the gas; the splint will relight in oxygen.

What happens when carbon dioxide is bubbled through limewater?

It turns milky (cloudy).

How can you test for ammonia gas?

Damp red litmus paper turns blue, and it forms white smoke of ammonium chloride when HCl gas is held near.

What color will damp litmus paper turn when exposed to chlorine gas?

Bleached and turns white.

How do you perform a flame test?

Take a sample of the metal on a wire and put it in a flame; the flame will change color based on the metal.

What is the flame color for lithium cations (Li+)?

Red.

What flame color indicates the presence of sodium cations (Na+)?

Yellow.

What is the flame color for potassium cations (K+)?

Lilac.

What flame color is produced by calcium cations (Ca2+)?

Orange-red.

What color does copper cations (Cu2+) produce in a flame test?

Blue-green.

What is the result of adding NaOH(aq) to NH4+?

It produces ammonia gas (NH3) and damp red litmus paper turns blue.

What color precipitate is formed when copper(II) is tested with NaOH(aq)?

Blue precipitate.

What precipitate color results from testing Fe2+ with NaOH(aq)?

Green precipitate.

What color precipitate does Fe3+ produce when tested with NaOH(aq)?

Brown precipitate.

How do you test for chloride ions (Cl-) using silver nitrate?

Add dilute nitric acid, followed by silver nitrate; chloride gives a white precipitate.

How can you identify bromide ions (Br-) with silver nitrate?

Add dilute nitric acid, followed by silver nitrate; bromide gives a cream precipitate.

What precipitate color indicates iodide ions (I-) in a silver nitrate test?

Yellow precipitate.

How do you test for sulfate ions (SO4 2-)?

Add dilute hydrochloric acid followed by barium chloride; a white precipitate will form.

What happens when carbonate ions (CO3 2-) react with hydrochloric acid?

They produce carbon dioxide gas; bubbling through limewater will turn it cloudy if CO2 is present.

What is the test for the presence of water using anhydrous copper(II) sulfate?

Anhydrous copper(II) sulfate will turn blue when water is present.

How can you test the purity of water?

By evaporating it or measuring its boiling point.