Question 1: Define chlorine in terms of its chemical properties and symbol from the periodic table.

Answer: Chlorine is a yellow-green toxic gas with the chemical symbol Cl, commonly used as a disinfectant and bleaching agent.

Question 2: Explain the chemical test used to identify the presence of chlorine gas in a sample.

Answer: Chlorine gas reacts with damp litmus paper, turning it white due to bleaching. It also produces a white precipitate with silver nitrate solution.

Question 3: Describe the mechanism by which chlorine bleaches coloured substances.

Answer: Chlorine acts as an oxidising agent, breaking down coloured molecules and removing their colour by bleaching.

Question 1: Calculate the volume of chlorine gas (at room temperature and pressure) contained in 0.5 mol of Cl₂. (Use 24 dm³ per mol as molar volume).

Answer: 12 dm³

Question 2: A sample of chlorine gas reacts completely with 10 grams of sodium. Write the balanced chemical equation and calculate the amount of sodium required in moles.

Answer: 2Na + Cl₂ → 2NaCl; Moles of Na = 10 g / 23 g/mol ≈ 0.435 mol

Question 3: If a 2.5 mol sample of chlorine gas is collected, what is its mass in grams?

Answer: 2.5 mol × 70.9 g/mol ≈ 177.25 g

Question 1: Describe a safe method for collecting chlorine gas in the laboratory, including safety precautions.

Answer: Chlorine gas can be collected over water in a fume cupboard with appropriate protective gear, avoiding inhalation and contact. Use a gas delivery tube and ensure proper ventilation.

Question 2: Identify the variables involved in a chlorine gas test using damp litmus paper.

Answer: Independent variable: presence of chlorine gas; dependent variable: colour change of litmus paper; controlled variables: amount of water, paper type, exposure time.

Question 1: A sample of unknown gas turns damp litmus paper white and reacts with silver nitrate solution, producing a white precipitate. What is the gas likely to be, and what evidence supports this?

Answer: The gas is likely chlorine. The white bleaching of litmus and the formation of a white silver chloride precipitate confirm its presence.

Question 1: Explain why chlorine is used in water treatment and discuss potential health risks associated with its use.

Answer: Chlorine is used in water treatment to kill bacteria and other pathogens, making water safe to drink. However, excessive exposure can lead to health risks such as respiratory issues, skin irritation, and the formation of harmful chlorinated compounds.

Question 2: A factory releases chlorine gas into the atmosphere. Describe the environmental impacts and safety measures that should be taken.

Answer: Chlorine release can lead to air pollution, harm to aquatic and terrestrial life, and health hazards for nearby populations. Safety measures include proper containment, gas scrubbers, regular monitoring, and emergency response plans to prevent leaks and exposure.