Question 1: Halogens are non-metal elements found in Group 7 of the periodic table. They exist as diatomic molecules and show a trend in reactivity across the group. Explain why the reactivity of halogens decreases down the group.

Answer: Reactivity decreases down the group because the atomic size increases, making it harder for the atom to attract electrons and gain electrons during reactions.

Question 1: Define the term 'halogen' and name the elements in Group 7.

Answer: Halogens are non-metal elements in Group 7 of the periodic table, including fluorine, chlorine, bromine, iodine, and astatine.

Question 2: Describe the physical states of the halogens at room temperature from fluorine to astatine.

Answer: Fluorine and chlorine are gases, bromine is a liquid, iodine is a solid, and astatine is believed to be a solid or metalloid.

Question 3: Explain why halogens are good oxidising agents.

Answer: Halogens are good oxidising agents because they readily gain electrons to form halide ions, and their ability to do so increases with higher electronegativity.

Question 1: Calculate the concentration of chlorine gas in mol/dm³ if 5.6 grams of Cl₂ (molar mass = 70.9 g/mol) is contained in 2 dm³ of gas volume.

Answer: 0.04 mol/dm³

Question 2: A solution contains 0.2 mol of bromide ions (Br⁻). How many grams of bromine (Br₂) are required to produce this amount of bromide ions through oxidation?

Answer: 15.6 grams

Question 1: Design a simple experiment to test the reactivity of chlorine with different metals. Mention the variables you would control and safety precautions to observe.

Answer: See full answer key

Question 2: Explain why it is important to wear protective equipment when handling halogens in the laboratory.

Answer: Halogens are toxic and corrosive; protective equipment prevents skin contact, inhalation, and eye injuries.

Question 1: A student measures the reactivity of chlorine, bromine, and iodine with a standard metal. The reactivity decreases in the order: chlorine > bromine > iodine. Explain the trend in reactivity across Group 7.

Answer: Reactivity decreases down the group because atomic size increases, reducing the ability of the halogen to attract and gain electrons from the metal.

Question 1: Explain how chlorine is used in water treatment and discuss the advantages and potential risks associated with its use.

Answer: See full answer key