module 3: 8.2 the halogens

Question 1

describe the trends of group 7 elements going down the group

Answer 1

going down there are:
more electrons
stronger London forces
more energy is required to break the intermolecular forces
increase in boiling point
less reactive

Question 2

Flourine appearance and state at RTP

Answer 2

pale yellow gas

Question 3

chlorine appearance and state at RTP

Answer 3

pale green gas

Question 4

bromine appearance and state at RTP

Answer 4

red-brown liquid

Question 5

iodine appearance and state at RTP

Answer 5

shiny grey-black solid

Question 6

Group 7 elements are ________ agents. they are _______

Answer 6

oxidising agents

they are reduced (gain electrons)

Question 7

chlorine solution in water

Answer 7

pale green

Question 8

bromine solution in water

Answer 8

orange

Question 9

iodine solution in water

Answer 9

brown

Question 10

chlorine solution in cyclohexane (top layer)

Answer 10

pale green

Question 11

bromine solution in cyclohexane (top layer)

Answer 11

orange

Question 12

iodine solution in cyclohexane (top layer)

Answer 12

violet

Question 13

the trend in reactivity of the halogens

Answer 13

going down the group
atomic radius increases
more inner shells so shielding increases
less nuclear attrition to capture an electron from another species
reactivity decreases

Question 14

define the term disproportionation reaction

Answer 14

a disproportionation reaction is a redox reaction in which the same element is both oxidised and reduced

Question 15

chlorine and water reaction

Answer 15

Cl2 + H2O –> HClO + HCl
chlorine is reduced: 0 –> -1
chlorine is oxidised: 0 –> +1

Question 16

chlorine reacting with cold, dilute aq NaOH

Answer 16

CL2 + 2NaOH –> NaClO + NaCl + H2O
chlorine is reduced: 0 –> -1
chlorine is oxidised: 0 –> +1

Question 17

benefits of chlorine use

Answer 17

ensures that the water is safe to drink and bacteria are killed

Question 18

precipitation reaction with aq silver ions

Answer 18

Ag+ + X- –> AgX