8.2 Halogens

Question 1

Group 7 reactivity trend of electronegativity down the group

Answer 1

decreases
as sheilding increaes
less attraction

Question 2

as you go down group 7 Boiling point…… becuase….

Answer 2

increases because more electrons therefore stronger london forces require more energy to overcome

hence yellow gas, green gas,red/brown liquid, grey blck solid,

Question 3

as you go down group 7 the oxidation power ….

Answer 3

decreases beacuase

Question 4

reactivity trend in Grp 7 down the group becuase…

Answer 4

• Reactivity decreases down the group
• atomic radius increases
• sheilding increases
• less nuclear attractrion to capture an electron
  so reactivity decreases

Question 5

Halide displacement reactions how are they recorded and how can we make the observation clearer?

Answer 5

a positive result is a change in colour
you can add organic solvent eg. hexane and the non polar halogen will dissovle readily in the non- polar solvent and settle as a distinct layer on top

Question 6

what colours do Cl,br,i go in water?

Answer 6

Cl pale green
Br orange
I brown

Question 7

what colours do Cl,br,i go in cyclohexane?

Answer 7

Cl pale green
Br orange
I violet

Question 8

Halogen disproportionaltion reactions

Answer 8

There are 2 common disproportionation reactions that involve chlorine.

1. Chlorine with water
2. Chlorine with HOT and COLD dilute sodium hydroxide.

Question 9

Chlorine and water

Answer 9

Cl2(aq) + H2O(l) → HCl(aq) + HClO(aq)

Chlorine is reduced

Chlorine is oxidised

Question 10

HOT Chlorine and sodium hydroxide:

Answer 10

3Cl2(aq) + 6NaOH(aq) → 5NaCl(aq) + NaClO3(aq) + 3H2O(l)

Question 11

COLDChlorine and sodium hydroxide:

Answer 11

Cl2(aq) + 2NaOH(aq) → NaCl(aq) + NaOCl(aq) + H2O(l)

Question 12

Chlorate(1) ions are used to

Answer 12

kill bacteria

Question 13

benefits of using cl in water purification

Answer 13

Chlorine removes many unpleasant
tastes from drinking water.

Chlorine helps to stop microorganisms
growing in water storage tanks

Some of the chlorine containing
chemical stays in the water. This
means that it can protect against
possible contamination in the pipes
that carry water from the treatment
works to the consumer.

Question 14

Risks of using cl in water purification

Answer 14

• cl2 gas is harmful to be inhaled it can irritate the repiritory system
• can also irritate skin anfd cause burns
• ## chlorine can react with organic compounds in water and from chlorinated hydrocarbons. some can be carcinogenic