Question 1: Chlorine is a halogen gas commonly used in water treatment and chemical manufacturing. Its reactivity makes it useful but also requires careful handling in engineering applications. Understanding its properties helps engineers design safer and more effective processes.

Answer: Chlorine is a reactive halogen gas used in water treatment and industry, requiring careful handling due to its reactivity.

Question 1: Define the term 'halogen' and explain why chlorine is classified as one.

Answer: A halogen is a group 17 element that is highly reactive and forms salts; chlorine is a halogen because it belongs to this group and shares these properties.

Question 2: Describe the chemical test used to identify chlorine gas in a laboratory setting.

Answer: Chlorine gas is identified by its bleaching action on damp litmus paper and its ability to produce a white precipitate with silver nitrate solution.

Question 1: An engineer needs to check for the presence of chlorine gas leaking from a pipeline. Describe a safe method to test for chlorine gas on-site.

Answer: Use damp blue litmus paper placed cautiously near the leak; if chlorine is present, the paper will bleach and turn white. Ensure proper ventilation and wear protective equipment.

Question 2: Identify two safety precautions that must be taken when handling chlorine gas in an industrial environment.

Answer: Use appropriate personal protective equipment (PPE) such as gloves and masks; ensure proper ventilation and have emergency spill kits available.

Question 1: Calculate the volume of chlorine gas (in litres) at room temperature and pressure (25°C, 1 atm) needed to react completely with 10 grams of sodium iodide (NaI). The reaction is: Cl₂ + 2NaI → 2NaCl + I₂

Answer: Using molar masses: NaI = 149 g/mol, Cl₂ = 70.9 g/mol. Moles of NaI = 10 g / 149 g/mol ≈ 0.067 mol. From the balanced equation, 1 mol Cl₂ reacts with 2 mol NaI, so moles of Cl₂ needed = 0.067 / 2 ≈ 0.0335 mol. Volume of Cl₂ = moles × molar volume at RTP (24 L/mol) ≈ 0.0335 mol × 24 L/mol ≈ 0.804 L.

Question 1: An industrial water treatment plant uses chlorine gas to disinfect water. The plant reports a chlorine consumption of 500 kg per day. If the chlorine is supplied as a compressed gas at 150 atm and 20°C, estimate the approximate volume of chlorine gas required daily. Assume ideal gas behaviour and a molar mass of 70.9 g/mol for Cl₂.

Answer: Moles of Cl₂ = 500,000 g / 70.9 g/mol ≈ 7057 mol. Using the ideal gas law, PV = nRT. At 20°C (293 K), R = 8.314 J/(mol·K). Convert pressure to Pascals: 150 atm = 150 × 101325 Pa = 15,198,750 Pa. V = nRT / P = (7057 mol) × 8.314 J/(mol·K) × 293 K / 15,198,750 Pa ≈ 1.138 × 10^3 m³ or 1138 m³. Therefore, approximately 1138 cubic meters of chlorine gas are required daily.