1. 1
   A student adds a small amount of manganese(IV) oxide catalyst to hydrogen peroxide solution in a conical flask, and a colourless gas is rapidly produced. The student inserts a glowing splint into the mouth of the flask.

   (a)

   Which observation confirms the gas is oxygen?

   [1 mark]

   • AThe splint is extinguished
   • BA squeaky pop is heard
   • CThe splint relights
   • DThe gas turns limewater cloudy

   (b)

   What role does the manganese(IV) oxide play in this reaction?

   [1 mark]

   • AIt is a catalyst that speeds up the decomposition of hydrogen peroxide
   • BIt is oxidised and used up in the reaction
   • CIt reacts with the oxygen produced
   • DIt is the limiting reactant

   (c)

   Explain, in terms of why a glowing splint relights, why oxygen gives a positive result in this test.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   During the electrolysis of dilute sulfuric acid, a colourless gas collects at the positive electrode (anode) in half the volume of the gas collected at the cathode.

   (a)

   To confirm this anode gas is oxygen, which test should be applied?

   [1 mark]

   • ALighted splint test
   • BGlowing splint test
   • CDamp litmus paper test
   • DLimewater test

   (b)

   The student inserts a glowing splint into the gas collected at the anode, and it relights and burns brightly. What can be concluded?

   [1 mark]

   • AThe gas is hydrogen
   • BThe gas is a mixture of hydrogen and oxygen
   • CThe gas is carbon dioxide
   • DThe gas is oxygen

   (c)

   Describe how the student should prepare the glowing splint before use, and explain what result would indicate the gas at the anode was NOT oxygen.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A biology teacher wants to demonstrate that green pondweed produces oxygen during photosynthesis. The teacher plans to collect gas bubbles given off by the pondweed under bright light in an inverted funnel and test tube arrangement.

   (a)

   Describe how the teacher should collect and test the gas to confirm it is oxygen.

   [3 marks]

   (b)

   A student in the class suggests that the gas could instead be carbon dioxide, since plants also release carbon dioxide during respiration. Explain how the teacher could use two different tests to distinguish clearly between oxygen and carbon dioxide, describing the result expected for each gas in each test.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hospital engineer must verify that a cylinder labelled "medical oxygen" genuinely contains oxygen gas before it is connected to patient equipment, since supplying the wrong gas could be dangerous.

   (a)

   Describe, in detail, a safe and reliable procedure the engineer could follow to test a small sample of the gas from the cylinder, including precautions.

   [6 marks]

   (b)

   The engineer performs the glowing splint test and observes only a faint, brief brightening of the splint rather than a strong relighting. Evaluate what this result might mean, and discuss what further steps the engineer should take before concluding whether the cylinder is safe to use.

   [6 marks]

   Total for question 4: 12 marks

End of questions