The halogens chlorine, bromine and iodine show trends in chemical and physical properties down the group. Table 3.1 shows some properties of chlorine, bromine and iodine. Table 3.1 property | chlorine | bromine | iodine ---|---|---|--- colour and state at room temperature | green gas | | bond energy/kJ mol–1 | 242 | 193 | 151 electronegativity | 3.0 | 2.8 | 2.5 formula of sodium halide | NaCl | NaBr | NaI

1. (a)(i)Complete Table 3.1. [1][1]
2. (a)(ii)The bond energy values in Table 3.1 refer to the X–X bond where X is the halogen. Explain the trend in the bond strength of the X—X bond in the halogens. [2][2]
3. (b)Explain, with the use of an equation, how chlorine, Cl2, is used in water purification. State the role of the active species produced. [2][2]
4. (c)The sodium halides in Table 3.1 also show trends in chemical properties.
5. (c)(i)Identify the sodium halide that reacts with concentrated H2SO4 to form H2S. [1][1]
6. (c)(ii)Identify the sodium halide that only undergoes a Brønsted-Lowry acid-base reaction with concentrated H2SO4. [1][1]
7. (c)(iii)A student adds a few drops of AgNO3(aq) to a solution of NaBr(aq). State what is observed. [1][1]
8. (d)Iodine monobromide, IBr, is a dark red solid that melts near room temperature. IBr reacts with propene. The mechanism for this reaction is the same as the mechanism for that of HBr with propene.
9. (d)(i)Identify all the intermolecular forces that exist between molecules of IBr. [1][1]
10. (d)(ii)Name the mechanism involved in the reaction of IBr with propene. [1][1]
11. (d)(iii)The reaction of IBr with propene forms two structural isomers. Draw the two structural isomers shown by these molecules. [2][2]
12. (d)(iv)Identify the type of structural isomerism shown by the molecules in (d)(iii). [1][1]
13. (d)(v)Explain why the two structural isomers do not form in equal amounts. [2][2]