Question 1: Group 7 elements, known as halogens, include fluorine, chlorine, bromine, iodine, and astatine. They are non-metals with seven electrons in their outermost shell and tend to form salts with metals. Their reactivity decreases down the group.

Answer: Halogens are non-metals with seven outer electrons, form salts, and reactivity decreases down the group.

Question 1: Define a halogen and list all the elements in Group 7.

Answer: A halogen is a non-metal in Group 7 of the periodic table; the elements are fluorine, chlorine, bromine, iodine, and astatine.

Question 2: Explain why the reactivity of halogens decreases as you move down Group 7.

Answer: Reactivity decreases down the group because the outermost electrons are farther from the nucleus, making it harder for the atom to gain an electron.

Question 1: Calculate the molecular formula of iodine monochloride if it contains 55.2% iodine by mass and 44.8% chlorine. (Atomic masses: I = 127 g/mol, Cl = 35.5 g/mol)

Answer: The molecular formula is ICl.

Question 2: A sample contains 0.5 mol of bromine and 1 mol of sodium. Write the formula of the compound formed and calculate the mass of the compound formed. (Atomic masses: Na = 23 g/mol, Br = 80 g/mol)

Answer: The formula is NaBr. Mass = (1 mol × 23 g/mol) + (0.5 mol × 80 g/mol) = 23 g + 40 g = 63 g.

Question 1: Describe a safe method to test the reactivity of chlorine gas with a metal sample. Include safety precautions.

Answer: Use a small amount of chlorine gas in a well-ventilated area or fume cupboard, wear protective gloves and goggles, and conduct the test with a suitable metal like iron or zinc.

Question 2: Identify the variables in an experiment testing the reaction of bromine water with an alkene.

Answer: Independent variable: type of alkene; Dependent variable: amount of bromine water decolourised; Control variables: temperature, concentration of bromine water, and volume of alkene.

Question 1: A reaction between chlorine and sodium produces a white solid and a gas that turns damp blue litmus paper red. Identify the products formed and explain the observations.

Answer: The products are sodium chloride (white solid) and chlorine gas. The gas turns damp blue litmus paper red because it is acidic, indicating the presence of chlorine gas.

Question 1: Explain the trend in melting points of the halogens down Group 7 and give reasons for this trend.

Answer: Melting points increase down Group 7 because the size of the molecules increases, resulting in stronger London dispersion forces which require more energy to break.

Question 2: A sample of chlorine gas reacts with sodium metal. Write the balanced chemical equation and describe the safety precautions necessary for this reaction.

Answer: 2Na + Cl₂ → 2NaCl. Conduct the reaction in a fume cupboard, wear protective gloves and goggles, and handle sodium carefully to prevent reactions with moisture.

Question 1: Describe how chlorine is used in water treatment and why it is important.

Answer: Chlorine is added to water supplies to kill bacteria and other pathogens, making water safe to drink and preventing the spread of diseases.

Question 2: Explain the importance of iodine in medicine and daily life.

Answer: Iodine is used in antiseptics and medical imaging, and it is essential for the production of thyroid hormones in the human body.