Question 1: Define what a halide ion is and give three examples.

Answer: A halide ion is a negatively charged ion of a halogen element, such as chloride (Cl⁻), bromide (Br⁻), or iodide (I⁻).

Question 2: Describe the general chemical reaction involved when a halide ion reacts with silver nitrate solution.

Answer: The halide ion reacts with silver nitrate (AgNO₃) to form a precipitate of silver halide: Ag⁺ + X⁻ → AgX (s), where X⁻ is the halide ion.

Question 3: Explain why silver chloride forms a white precipitate, whereas silver iodide forms a yellow precipitate.

Answer: The different colours are due to differences in the crystal structures and the wavelength of light absorbed; silver chloride is white, and silver iodide is yellow due to their distinct lattice energies and absorption spectra.

Question 1: Outline the steps involved in testing a sample for the presence of halide ions using silver nitrate solution, including safety precautions.

Answer: First, prepare a dilute sample of the solution to be tested. Add a few drops of dilute nitric acid to remove interference from other ions. Then, add a few drops of silver nitrate solution. Observe the colour of any precipitate formed. Wear safety goggles and gloves when handling chemicals, and dispose of waste according to safety guidelines.

Question 2: Identify the limiting factor if a student notices that no precipitate forms when testing a chloride sample with silver nitrate.

Answer: The sample may not contain halide ions, or the concentration of halides is too low to produce a visible precipitate.

Question 1: A student adds silver nitrate to four different solutions, and observes the following precipitates: Solution A - White; Solution B - Cream; Solution C - Yellow; Solution D - No precipitate. Match each solution to the likely halide ion present.

Answer: Solution A: Chloride (Cl⁻), Solution B: Bromide (Br⁻), Solution C: Iodide (I⁻), Solution D: No halide ions present.

Question 2: Based on the data provided, which halide ion produces the most soluble silver halide precipitate under typical conditions, and why?

Answer: Silver chloride is the most soluble among the silver halides under typical conditions because it has the lowest lattice energy, making it less insoluble compared to bromide and iodide precipitates.

Question 1: Calculate the concentration of chloride ions in a sample if 25.0 cm³ of the sample produces a precipitate with 10.0 cm³ of 0.1 mol/dm³ silver nitrate solution. (Assume complete reaction and no side reactions.)

Answer: Concentration of Cl⁻ = (C₁V₁) / V₂ = (0.1 mol/dm³ × 10.0 cm³) / 25.0 cm³ = 0.04 mol/dm³.

Question 2: If the molar mass of silver chloride (AgCl) is 143.32 g/mol, calculate the mass of AgCl formed from 0.1 dm³ of a 0.04 mol/dm³ chloride solution.

Answer: Mass of AgCl = moles × molar mass = (0.04 mol/dm³ × 0.1 dm³) × 143.32 g/mol = 0.574 g.

Question 1: Explain how the analysis of halide ions is used in the water treatment industry.

Answer: Halide analysis helps detect contamination and ensure water quality by identifying the presence of chloride, bromide, or iodide ions, which can affect water taste, corrosion, and safety.

Question 2: Describe one technological application that relies on halide ions and discuss its importance.

Answer: Halide ions are crucial in photographic film development, where silver halides (like silver bromide) are used due to their light-sensitive properties. This technology revolutionised photography by enabling high-quality image capture and development.