Question 1: Oxygen is a colourless, odourless gas that supports combustion. It makes up about 21% of the Earth's atmosphere. In laboratory tests, oxygen can be identified using specific methods. Explain the principle behind the test for oxygen using a glowing splint.

Answer: When a glowing splint is placed in oxygen, it relights because oxygen supports combustion, reigniting the glowing splint.

Question 2: Describe the mechanism by which oxygen supports combustion in a test tube experiment.

Answer: Oxygen reacts with the fuel in the flame, increasing the combustion rate and causing the flame to rekindle or burn more brightly.

Question 1: Define oxygen in terms of its chemical composition.

Answer: Oxygen is a diatomic molecule with the chemical formula O2.

Question 2: Explain why oxygen is essential for most forms of life on Earth.

Answer: Oxygen is essential for respiration, a process that releases energy from food in most living organisms.

Question 1: Calculate the volume of oxygen (O2) at room temperature and pressure (RTP) occupied by 2 moles of oxygen gas. (Use the molar volume of 24 dm³/mol at RTP.)

Answer: Volume = 2 mol × 24 dm³/mol = 48 dm³

Question 2: If 16 grams of oxygen gas are available, how many moles does this represent? (Molar mass of O2 = 32 g/mol.)

Answer: Number of moles = 16 g ÷ 32 g/mol = 0.5 mol

Question 1: Outline the key safety precautions to observe when handling oxygen in a laboratory setting.

Answer: Ensure good ventilation, avoid open flames or sparks, handle cylinders securely, and wear safety goggles and gloves.

Question 2: Design a simple experiment to test for oxygen using a glowing splint. State the variables you would control and measure.

Answer: Insert a glowing splint into a test tube containing oxygen. Control variables such as temperature and pressure. Measure the time taken for the splint to relight and compare it with results in other gases.

Question 1: A student measures the volume of oxygen produced from the decomposition of potassium chlorate (KClO3) and records a volume of 48 dm³ at RTP. If the decomposition produces 1 mole of oxygen gas, does this data support the theoretical molar volume of 24 dm³ per mole? Explain your reasoning.

Answer: Yes. 48 dm³ corresponds to 2 moles of oxygen (since 2 × 24 dm³ = 48 dm³), indicating the data is consistent if 2 moles were produced. If only 1 mole was expected, the volume is double, suggesting excess oxygen or measurement error.

Question 2: A sample of oxygen was tested using a glowing splint, which relit after 10 seconds. Another sample took 30 seconds to relight. What might account for the difference in relighting times?

Answer: The sample with a shorter relight time likely had a higher concentration or purity of oxygen, while the longer time indicates possible impurities or lower oxygen concentration.

Question 1: Describe how oxygen is used in medical treatments and why its purity is important.

Answer: Oxygen is administered to patients with respiratory issues to support breathing; high purity ensures safe and effective treatment without harmful impurities.

Question 2: Explain the role of oxygen in the steel-making industry and how it benefits the process.

Answer: Oxygen is used to remove impurities like sulphur and carbon from molten iron, producing steel more efficiently and improving its quality.