GCSE Chemistry - Analysis Tests

1. What test is used to detect Hydrogen (H₂) gas?  

Lit splint – Squeaky pop 🎈

Tip to remember: Hydrogen makes a high-pitched pop like a balloon popping.

2. What test is used to detect Oxygen (O₂) gas? 

Answer: Glowing splint – Relights 🔥

Tip to remember: Oxygen helps things burn, so it relights the splint. 

3. How do you test for Carbon Dioxide (CO₂)? 

Answer: Bubble through limewater – Turns milky/cloudy ☁

Tip to remember: Think "Cloudy CO₂". 

4. What test is used to detect Chlorine (Cl₂) gas? 

Answer: Damp blue litmus paper – Turns white (bleached) 🧼

Tip to remember: Chlorine is in bleach, so it bleaches the paper. 

5. What test detects Ammonia (NH₃)? 

 

 

Answer: Damp red litmus paper – Turns blue 🧪 

Tip to remember: Ammonia is alkaline, so "A for Ammonia, A for Alkaline." 

6. What is the flame color for Lithium (Li⁺)? 

Answer: Crimson red ❤

Tip to remember: "Love is Red." 

7. What flame color is observed for Sodium (Na⁺)? 

Answer: Yellow/orange 🧀 

Tip to remember: "Nacho cheese is yellow." 

8. What flame color indicates Potassium (K⁺)? 

Answer: Lilac/Purple 👑 

Tip to remember: "King’s Royal Purple." 

9. What flame color indicates Calcium (Ca²⁺)? 

 

Answer: Brick red 🧱 

Tip to remember: "Red Cat bricks." 

10. What flame color indicates Copper (Cu²⁺)? 

 Answer: Blue-green 🥒

Tip to remember: "Cucumbers are green."

11. How do you perform a flame test? 

Answer: Dip a nichrome/platinum wire loop in HCl to clean it. Hold it in a blue Bunsen burner flame. Observe the colour and match it to the table. 

12. What is the precipitate color for Copper (Cu²⁺) when reacted with Sodium Hydroxide (NaOH)? 

Answer: Blue ☁

Tip to remember: "Copper sky is blue." 

13. What is the precipitate color for Iron (II) (Fe²⁺) when reacted with NaOH? 

Answer: Green 🟢🟢

Tip to remember: "Iron II - Think of the 2 green Hulk fists!" 

14. What precipitate color appears when Iron (III) (Fe³⁺) reacts with NaOH? 

Answer: Brown 🏚

Tip to remember: "Iron III - Rusty brown." 

15. What precipitate is observed for Aluminium (Al³⁺) with NaOH? 

Answer: White, dissolves in excess NaOH 🔄 

Tip to remember: "Aluminium Always dissolves." 

16. What precipitate is observed for Calcium (Ca²⁺) with NaOH? 

Answer: White, does NOT dissolve in excess NaOH 🚫

Tip to remember: "Can’t dissolve." 

17. What precipitate is observed for Magnesium (Mg²⁺) with NaOH? 

Answer: White, does NOT dissolve in excess NaOH 📌

Tip to remember: Same as calcium, so just memorise together! 

18. What test is used to detect Carbonates (CO₃²⁻)? 

Answer: Add dilute acid – Fizzes (CO₂ produced) 🫧 

Tip to remember: "Carbonates Create Carbon Dioxide Bubbles." 

19. How do you test for Sulfates (SO₄²⁻)? 

Answer: Add HCl + BaCl₂ – White precipitate (BaSO₄) ☁

Tip to remember: "Sulfur smoke is white." 

20. How do you test for Chlorides (Cl⁻)? 

Answer: Add Nitric acid + AgNO₃ – White precipitate 🌨

Tip to remember: "Cloudy White for Chloride." 

 

21. How do you test for Bromides (Br⁻)? 

Answer: Add Nitric acid + AgNO₃ – Cream precipitate ☕

Tip to remember: "Bromide is Beige/Cream." 

22. How do you test for Iodides (I⁻)? 

Answer: Add Nitric acid + AgNO₃ – Yellow precipitate 🎨

Tip to remember: "Iodide is like Inky Yellow." 

23. How do you test for Water using Anhydrous Copper (II) Sulfate (CuSO₄)? 

Answer: White → Blue 💧

Tip to remember: "White CuSO₄ is Thirsty for Water." 

24. How do you test for Water using Cobalt Chloride Paper? 

 

Answer: Blue → Pink 🌅

Tip to remember: "Think of blue to pink like a sunset."

25. What is the boiling and freezing point of pure water? 

Answer: Boils at 100°C, Freezes at 0°C 🧊🔥

Tip to remember: Pure water always sticks to these values.