Combined Science: Chemistry IGCSE
Practice Exam Answered Correctly.
What is the effect of adding NaOH to iron (III) (Fe³⁺)? Then adding ammonia solution? - Answer Adding
NaOH: red/brown precipitate. Insoluble in excess.
Adding ammonia solution: same as before.
What is the effect of adding NaOH to zinc (Zn)? Then adding ammonia solution? - Answer Adding
NaOH: white precipitate forms. Dissolves in excess to form colourless solution.
Adding ammonia solution: same as before.
State the colours for lithium (Li⁺), sodium (Na⁺), potassium (K⁺), and copper (Cu²⁺) - Answer In order:
red, yellow, lilac, blue/green
How can you identify carbonates (CO₃²⁻)? - Answer Test: add dilute acid and test the gas released.
Result: gas produced is CO₂, turns limewater milky.
How can you identify chlorides (Cl⁻)? - Answer Test: acidify with dilute nitric acid and add aqueous
silver nitrate
Result: white precipitate is formed.
How can you identify nitrates (NO₃²⁻)? - Answer Test: add aqueous NaOH and aluminium fil, warm
gently and test the gas released.
Result: ammonia gas is given off. Has a pungent smell and turns litmus blue.
How can you identify sulfates (SO₄²⁻)? - Answer Test: acidify with dilute nitric acid and add aqueous.
barium nitrate.
Result: white precipitate is formed.
Practice Exam Answered Correctly.
What is the effect of adding NaOH to iron (III) (Fe³⁺)? Then adding ammonia solution? - Answer Adding
NaOH: red/brown precipitate. Insoluble in excess.
Adding ammonia solution: same as before.
What is the effect of adding NaOH to zinc (Zn)? Then adding ammonia solution? - Answer Adding
NaOH: white precipitate forms. Dissolves in excess to form colourless solution.
Adding ammonia solution: same as before.
State the colours for lithium (Li⁺), sodium (Na⁺), potassium (K⁺), and copper (Cu²⁺) - Answer In order:
red, yellow, lilac, blue/green
How can you identify carbonates (CO₃²⁻)? - Answer Test: add dilute acid and test the gas released.
Result: gas produced is CO₂, turns limewater milky.
How can you identify chlorides (Cl⁻)? - Answer Test: acidify with dilute nitric acid and add aqueous
silver nitrate
Result: white precipitate is formed.
How can you identify nitrates (NO₃²⁻)? - Answer Test: add aqueous NaOH and aluminium fil, warm
gently and test the gas released.
Result: ammonia gas is given off. Has a pungent smell and turns litmus blue.
How can you identify sulfates (SO₄²⁻)? - Answer Test: acidify with dilute nitric acid and add aqueous.
barium nitrate.
Result: white precipitate is formed.
