Question 1: Explain what halide ions are and why their detection is important in space exploration missions.

Answer: Halide ions are negatively charged ions of halogen elements (fluoride, chloride, bromide, iodide). Detecting them helps identify the presence of certain minerals or compounds on celestial bodies, which can give insights into planetary composition and the potential for life.

Question 2: Describe the typical chemical test used to identify chloride ions in a laboratory setting.

Answer: Chloride ions are tested by adding dilute nitric acid followed by silver nitrate solution; a white precipitate of silver chloride confirms their presence.

Question 3: In space exploration, why might scientists use portable ion test kits instead of laboratory equipment?

Answer: Portable ion test kits allow for rapid, on-site analysis of samples from celestial bodies, saving time and reducing the need to transport samples back to Earth for testing.

Question 4: Calculate the amount of silver nitrate solution needed to test 10 mL of a water sample suspected to contain chloride ions, assuming a 1:1 molar ratio. (Molar mass of AgNO₃ = 169.87 g/mol)

Answer: 0.01 mol of AgNO₃ needed; mass = 0.01 mol × 169.87 g/mol = 1.6987 g. Therefore, approximately 1.7 g of silver nitrate solution is required.

Question 5: Identify the safety precautions that must be taken when handling silver nitrate in space research laboratories.

Answer: Wear gloves and eye protection, handle in a well-ventilated area, and avoid contact with skin and eyes as silver nitrate is corrosive and can stain skin.

Question 6: A sample from a moon surface shows a brown precipitate when tested with potassium iodide solution. What halide ion is present?

Answer: Iodide

Question 7: Fill in the blank: The presence of bromide ions in a sample can be confirmed by adding silver nitrate solution, which forms a __________ precipitate.

Answer: cream

Question 8: Discuss how the detection of halide ions on Mars could contribute to our understanding of the planet's history and potential habitability.

Answer: Detecting halide ions such as chloride and bromide on Mars can reveal the presence of water-related minerals and past aqueous activity. This information helps scientists understand the planet's geological history, the availability of essential elements for life, and assesses its potential habitability for future exploration.

Question 9: Which of the following is a common method for detecting iodide ions in a sample?

Answer: Adding silver nitrate solution

Question 10: Describe an experiment to differentiate between chloride, bromide, and iodide ions in a single water sample.

Answer: Add dilute nitric acid to the sample to remove carbonate impurities, then add silver nitrate solution separately to small portions of the sample. Observe the colour of the precipitates: white for chloride, cream for bromide, and yellow for iodide. Confirm by adding dilute ammonia solution: chloride dissolves first, bromide with concentrated ammonia, while iodide remains insoluble.