IGCSE Colours and Tests

Alkanes and bromine water

• remains orange
• orange goes to colourless

Chlorine with damp litmus

• blue goes to red then white/bleached
• blue goes to red
• white goes blue
• red goes to blue

Test for the presence of water - anhydrous copper sulphate

• white goes to blue
• blue goes to red
• blue goes to red then white/bleached
• red goes to blue

Reaction of iron(II) salts with sodium hydroxide - test for Fe2+

• green solution goes to green precipitate.

• orange brown solution goes to red brown precipitate.

• blue solution and colourless solution goes to light blue precipitate.

• white precipitate forms

Reaction of iron(III) salts with sodium hydroxide - test for Fe3+

• orange brown solution goes to red brown precipitate.

• green solution goes to green precipitate.

• blue solution and colourless solution goes to light blue precipitate.

• colourless solution goes to white precipitate

Test for bromide ion. Acidify with dilute nitric acid, then add aqueous silver nitrate

• colourless solution goes to pale cream precipitate.
• colourless solution goes to white precipitate.
• colourless solution goes to yellow precipitate.
• green solution goes to green precipitate.

Test for sulfate ion. Acidify with hydrochloric acid, then add aqueous barium chloride.

• colourless solution goes to white precipitate.
• colourless solution goes to yellow precipitate.
• colourless solution goes to pale cream precipitate.

Zinc or magnesium in copper sulphate solution

• grey metal in blue solution goes to colourless solution and pink-brown solid
• green solid goes to black solid
• colourless solution goes to white precipitate. White precipitate is barium sulfate.
• colourless solution goes to yellow precipitate. Yellow precipitate is silver iodide.

Bromine water and sodium iodide solution

• two colourless solutions goes to yellow-orange solution

• two colourless solutions goes to brown solution

• pale yellow-orange solution turns darker

• two colourless gases goes to white solid

Test for potassium ion. Flame test.

• Lilac colour

• Red colour.

• Green colour

• Orange colour