Group 7

Question 1

State and appearance of halogens at room temperature

Answer 1

Fluorine: yellow gas
Chlorine: green gas
Bromine: orange/brown liquid
Iodine: dark grey solid

Question 2

Colour of vapour for halogens

Answer 2

Bromine: orange
Iodine: purple

Question 3

Colour in polar solvent for halogens

Answer 3

Chlorine: very pale green to colourless
Bromine: orange bromine water
Iodine: brown iodine solution

Question 4

Colour in non-polar solvents

Answer 4

Chlorine: green
Bromine: orange
Iodine: violet

Question 5

Describe the trend in atomic radius down group 7

Answer 5

It increases

Question 6

Explain the change in atomic radius down group 7

Answer 6

More electrons, so more shells, so distance between nucleus and outer shell is greater

Question 7

Describe the trend in electronegativity down group 7

Answer 7

It decreases

Question 8

Explain the trend in electronegativity in group 7

Answer 8

More shells, more shielding, and bigger atomic radius - so weaker attraction between nucleus and outer shell electron

Question 9

Describe the trend in ionisation enthalpy in group 7

Answer 9

It decreases: More shells, more shielding, and bigger atomic radius - so weaker attraction between nucleus and outer shell electron

Question 10

Describe the trend in melting/boiling point down group 7

Answer 10

It increases

Question 11

Explain the trend in melting/boiling points down group 7

Answer 11

There are more electrons, so stronger Van der Waals’ forces between molecules which require more energy to overcome.

Question 12

Why is Chlorine added to water?

Answer 12

It kills bacteria at low levels. (Toxic at high levels!! ARGH!)

Question 13

What is produced in the reaction between Chlorine and water?

Answer 13

Hydrochloric acid and Chloric (I) acid

Question 14

What is the balanced equation for the reaction between Chlorine and water in the dark?
What type of reaction is this?

Answer 14

Cl2 (aq) + H2O (l) HCl (aq) + HClO (aq)

Redox disproportionation reaction

Question 15

What is the balanced equation for the reaction between Chlorine and water in the light?

Answer 15

2Cl2(aq) + 2H2O(l) –> 4HCl(aq) + O2(g)

Question 16

What is the balanced equation for the reaction between chlorine and sodium hydroxide?
What is the product commonly known as?

Answer 16

Cl2(aq) + 2NaOH(aq) –> NaCl(aq) + NaClO(aq) + H2O(l)

Bleach (the aqueous mixture of the products)

Question 17

What is an oxidising agent?

Answer 17

An element that is itself reduced so causes other elements to be oxidised.

Question 18

Describe the trend in reactivity down the group.

Answer 18

It decreases down the group

Question 19

Explain the trend in reactivity down the group.

Answer 19

Atomic radius increases, shielding increases - so the electrostatic attraction between the nucleus and the electron to be gained decreases

Question 20

What colour are halide ions?

Answer 20

colourless

Question 21

What is a reducing agent?

Answer 21

A substance that is itself oxidised so causes the other substance to be reduced.

Question 22

What is the best to worst halide reducing agent?

Answer 22

Iodide (can reduce H2SO4 to SO2, S and H2S)
Bromide (can reduce H2SO4 only to SO2)
Chloride (cannot reduce H2SO4)

Question 23

What observations are there for all potential products when H2SO4 is reduced?

Answer 23

SO2 is a colourless gas
S is a yellow solid
H2S is a colourless gas with a bad egg smell

Question 24

What are the observations for a halide acid-base reaction?

Answer 24

White steamy fumes of the hydrogen halide are produced.

Question 25

For which halide acid-base reactions does redox also take place?

Answer 25

Bromide and Iodide

Question 26

What are the observations for a reaction of silver nitrate with each halide?

Answer 26

Chloride: white precipitate formed and soluble in dil NH3
Bromide: cream precipitate, not soluble in dil NH3 but is in conc NH3
Iodide: yellow precipitate formed, insoluble in NH3