Chapter 9 - Group 2 and the Halogens

Question 1

What is the charge of a group 2 ion?

Answer 1

+2

Question 2

What do the electron configurations in group 2 end in?

Answer 2

s2

Question 3

Atomic radius ……… down group 2.

Answer 3

Increases

Question 4

Reactivity ……… down group 2.

Answer 4

Increases

Question 5

First ionisation energy ……… down group 2.

Answer 5

Decreases

Question 6

What is formed when group 2 elements react with water?

Answer 6

Metal hydroxides and hydrogen (except magnesium which forms an oxide)

Question 7

What state are group 2 oxides at room temperature?

Answer 7

White solids

Question 8

What group number are the halogens?

Answer 8

7 (or 17)

Question 9

What is the appearance of Fluorine at room temperature?

Answer 9

Pale yellow gas

Question 10

What is the appearance of Chlorine at room temperature?

Answer 10

Pale green gas

Question 11

What is the appearance of Bromine at room temperature?

Answer 11

Brown/orange liquid

Question 12

What is the appearance of Iodine at room temperature?

Answer 12

Grey solid

Question 13

Boiling points …….. down group 7.

Answer 13

Increase

Stronger induced dipole-dipole (London) forces require more energy to be broken.

Question 14

Electronegativity ……… down group 7.

Answer 14

Decreases

Atomic radius and shielding increases.

Question 15

During a displacement reaction, which organic solvent is added to help identify the halogen?

Answer 15

Hexane

Question 16

Reactivity ……… down group 7.

Answer 16

Decreases

Question 17

What happens when a halogen is reacted with a halide ion?

Answer 17

If the halogen is more reactive than the halide ion (lower on the periodic table), it will displace the halide ion. (e.g. Cl2 + 2Br = 2Cl- + Br2 as chlorine is more reactive than bromine)

Question 18

When reacted with silver nitrate, what colours are the precipitates of chloride, bromide, and iodide ions?

Answer 18

Chloride - white precipitate
Bromide - cream precipitate
Iodide - yellow precipitate

Question 19

Why is nitric acid added to precipitation reactions before the silver nitrate?

Answer 19

Nitric acid will react with any anions other than the halides, so that they will not react with the silver nitrate.

Question 20

How can the present halide in a precipitation reaction be identified using ammonia?

Answer 20

Chloride - precipitate dissolves in dilute NH3
Bromide - precipitate dissolves in concentrated NH3
Iodide - precipitate insoluble in concentrated NH3

Question 21

What is a disproportionation reaction?

Answer 21

Where one element is both oxidised and reduced simultaneously.

Question 22

What are the advantages of adding chlorine to drinking water?

Answer 22

• Destroys disease-causing microorganisms
• Reduces bacteria build up
• Reduces growth of algae in water

Question 23

What are the disadvantages of adding chlorine to drinking water?

Answer 23

• Chlorine gas is toxic and irritates the respiratory system
• Liquid chlorine can cause severe chemical burns to the skin
• Can react with organic compounds in the water to produce chloroalkanes, which have been linked to causing cancer.

Question 24

What is the test for ammonium ions?

Answer 24

Add NaOH, and shake. Hold damp red litmus paper over, and will turn blue if ammonium gas is produced.

Question 25

What is the test for carbonates?

Answer 25

Reacts with hydrochloric acid, then gas produced bubbled through limewater. If it turns cloudy, carbonates are present, and CO2 was produced.

Question 26

What is the test for sulphates?

Answer 26

Hydrochloric acid is added to remove any carbonates. Barium chloride is then added, and a white precipitate will form is sulphates are present.

Question 27

In what order should ions be tested for?

Answer 27

Carbonates
Sulphates
Halides

To prevent false positives