Chemical Tests

test for hydrogen + result

burning splint - catches fire with a squeaky pop

equation for hydrogen

2H₂ (g) + O₂ (g) → 2H₂O (l)

test for oxygen + result

glowing splint → relight

test for chlorine + result

damp blue litmus paper → bleaches

test for carbon dioxide + result

bubble through limewater → turns cloudy

equation for carbon dioxide

CO₂ (g) + Ca(OH)₂ → CaCO₃ (s) + H₂O (l)

test for ammonia + result

add sodium hydroxide solution

damp red litmus paper → turns blue

method for flame tests

clean nichrome wire in concentrated hydrochloric acid

• dip in sample

• hold in blue Bunsen burner flame

result for lithium

red

result for sodium

yellow

result for potassium

lilac

result for copper

blue/green

result for calcium

orange/red

copper hydroxide equation + precipitate

Cu²⁺(aq) + 2OH^- (aq) → Cu(OH)₂ (s) blue ppt

iron (II) hydroxide equation + precipitate

Fe²⁺(aq) + 2OH^- (aq) → Fe(OH)₂ (s) green ppt

iron (III) hydroxide equation

Fe³⁺ (aq) + 3OH^-(aq) → Fe(OH)₃ (s) orange/brown ppt

ammonium hydroxide equation

NH₄⁺ (aq) + OH^-(aq) -(heat→ NH₃ (g) + H₂O (l)

ammonium hydroxide test result

turns damp red litmus paper blue

test for water (not pure)

anhydrous copper (II) sulfate → hydrated copper (II) sulfate

test for carbonate

add dilute acid → HCl and then test using bubble through limewater

equation for calcium carbonate with dilute hydrochloric acid

CaCO₃ (s) + 2 HCl (aq) ⟶ CaCl₂ (aq) + CO₂ (g) + H₂O (l)

test for sulfate

add HCl to remove impurities and add barium chloride to form a white ppt

colour change for anhydrous copper sulfate and water

white → blue