Group 7

Question 1

Does the boiling point of group 7 metals increase/decrease going down the group? Why?

Answer 1

Increase due to increasing strength of VDW forces as the size and relative mass increases so more energy required to overcome the VDW forces so higher boiling point

Question 2

Does atomic radius increase/decrease going down group 7? Why?

Answer 2

Increases due to additional electron shells

Question 3

Describe the trends in reactivity going down group 7

Answer 3

They need to gain an electron. As atomic radius increases this becomes harder as the positive attraction of the nucleus is weakened by additional shielding. Therefore harder to attract an electron and so reactivity decreases down group

Question 4

Does the first ionisation energy of group 7 increase/decrease going down group? Why?

Answer 4

Decreases due to atomic radius and increased amounts of shielding

Question 5

Why do the halogens act as a good oxidising agent?

Answer 5

They accept electrons from the species being oxidised and are reduced. This oxidising power decreases down group as their ability to attract electrons decreases due to shielding and greater atomic radius. The relative oxidising strengths means a halogen will displace any halide beneath it in the periodic table

Question 6

What are the negative ions of halogens known as?

Answer 6

Halide ions

Question 7

Why are halide ions good reducing agents?

Answer 7

They donate electrons to the species being reduced and are themselves oxidised. This reducing power increases down group as electrons are easier to lose from larger ions due to shielding and larger atomic radius

Question 8

What is acidified silver nitrate used to test for? Why?

Answer 8

Halide ions as it reacts to form different coloured precipitates depending on ion present.

Question 9

If the precipitate formed is not clear to distinguish what can you further test with?

Answer 9

Ammonia

Question 10

What effect does the reducing power have on the length of the reaction? Why?

Answer 10

The greater the reducing power, the longer the reaction as the halide is powerful enough to reduce more species

Question 11

Describe the trend in electronegativity going up group 7

Answer 11

Increases going up the group

Question 12

State the colour, physical state and electron configuration of fluorine, F2?

Answer 12

Pale yellow
Gas
1s²2s²2p⁵

Question 13

State the colour, physical state and electron configuration of chlorine, Cl2?

Answer 13

Green
Gas
1s²2s²2p⁶3s²3p⁵

Question 14

State the colour, physical state and electron configuration of bromine, Br2?

Answer 14

Red-brown
Liquid
1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁵

Question 15

State the colour, physical state and electron configuration of iodine, I2?

Answer 15

Grey-black
Solid
1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁵

Question 16

What happens when you react concentrated NH3 with Cl- and Br-?

Answer 16

Precipitate dissolves

Question 17

What happens when you react concentrated NH3 with I-

Answer 17

No change

Question 18

What happens when you react dilute NH3 with Cl-?

Answer 18

Precipitate dissolves

Question 19

What happens when you react dilute NH3 with Br- and I-?

Answer 19

No change

Question 20

What happens when you react silver nitrate (AgNO3) with Cl-?

Answer 20

White precipitate (AgCl) forms

Question 21

What happens when you react silver nitrate (AgNO3) with Br-?

Answer 21

Cream precipitate (AgBr) forms

Question 22

What happens when you react silver nitrate (AgNO3) with I-?

Answer 22

Yellow precipitate (AgI) forms

Question 23

When chlorine reacts with cold water what does it produce?

Answer 23

Chlorate (l) ions (ClO-) and Chloride ions

Question 24

What type of reaction is it when chlorine reacts with cold water? Why?

Answer 24

Disproportion reaction as the chlorine is both oxidised and reduced. The oxidisation state goes from 0 to +1 and -1

Question 25

What can chlorine be used for?

Answer 25

used in small quantities to kill bacteria in water treatment processes

Question 26

How can chlorine be used in bleach production?

Answer 26

Cl can be mixed with cold, aqueous sodium hydroxide to produce sodium hypochlorite

Question 27

How do you test for halides?

Answer 27

Using acidified silver nitrate and ammonia

Question 28

How do you test for sulphates?

Answer 28

Using BaCl2 which reacts to form a white precipitate

Question 29

What do hydroxide ions indicate? How can they be identified?

Answer 29

Indicate that the substance is alkaline.
Can be identified with red litmus that turns blue or using universal indicator which turns blue-purple

Question 30

How do you test for carbonates?

Answer 30

Use HCL & limewater
When adding HCL to a carbonate it will fizz (effervescence) and produce CO2
CO2 when bubbled through it, turn clear limewater a cloudy milky white colour

Question 31

How can group 2 ions be identified?

Answer 31

Using flame tests

Question 32

What colour will the flame turn if Calcium ions are present?

Answer 32

Brick Red

Question 33

What colour will the flame turn if Strontium ions are present?

Answer 33

Red

Question 34

What colour will the flame turn if Barium ions are present?

Answer 34

Pale green

Question 35

How can you test to see if ammonium ions are present?

Answer 35

If present ammonia gas given off (a base). Presence can be tested by holding red litmus over a petri dish of the substance being tested. If present turn blue
OR can be tested same way but by adding NaOH to produce the ammonia gas faster