Group 7 (Halogens)

Question 1

How does the appearance of the halogens change going down the group?

Answer 1

they become darker and denser

Question 2

Why are many of the properties fluorine considered untypical?

Answer 2

• The F-F bond is weaker than expected
• This is because the F atoms are smaller and there is repulsion between non-bonding electrons

Question 3

Describe and explain the trend in electronegativity going down the group

Answer 3

Electronegativity decreases, as the atoms get larger and electron shielding increases therefore the electrostatic attraction between the nucleus and electrons decreases.

Question 4

Describe and explain the trend in boiling points down the group

Answer 4

Boiling points increase as the atoms get larger and have more electrons so the VDWs forces get stronger

Question 5

How does the oxidising ability of the halogens change going down the group?

Answer 5

It will decrease going down the group

Question 6

What happens in a displacement reaction?

Answer 6

Halogens react with metal halides in a solution in such a way that the halide in the compound will be displaced by a more reactive halogen

Question 7

How does the reducing power of the halogens change going down the group?

Answer 7

The halides become more reducing as you go down the group. The larger the ion, the more easily it can give away an electron

Question 8

What is the simplest ionic equation for the reaction of solid NaCl with concentrated sulfuric acid? What is an observation of this reaction?

Answer 8

Cl- + H2SO4 –> HCl + HSO4-
Steamy,white fumes, turns litmus paper red

Question 9

What is the simplest ionic equation for the reaction of solid NaBr with concentrated sulfuric acid? What is an observation of this reaction?

Answer 9

2Br- + H2SO4 + 2H+ –> Br2 + SO2 + 2H2O
Orange vapour and choking gas

Question 10

What are the ionic equations for the reaction of solid NaI with concentrated sulfuric acid? What are the observations of these reactions?

Answer 10

6I- + H2SO4 + 8H+ –> 3I2 + S + 4H2O
yellow solid produced and purple vapour
8I- + H2SO4 + 8H+ –> 4I2 + H2S + 4H2O
foul smelling gas and purple vapour

Question 11

The reaction of Cl and water is an example of what type of reaction?

Answer 11

disproportionation

Question 12

What is a disproportionation reaction?

Answer 12

A reaction where an element is being both reduced and oxidised.

Question 13

When using ammonia to test for Cl- ions, what is the expected result?

Answer 13

The ppt. will dissolve in dilute ammonia

Question 14

When using ammonia to test for Br- ions, what is the expected result?

Answer 14

The ppt. will dissolve in concentrated ammonia

Question 15

When using ammonia to test for I- ions, what is the expected result?

Answer 15

the ppt will not dissolve

Question 16

Give the equation for the reaction of chlorine with cold water

Answer 16

Cl2 + H2O -> HClO + HCl

Question 17

Give the equation of chlorine with water in the presence of UV light

Answer 17

2Cl2 + 2H2O -> 4HCl + O2

Question 18

What is a benefit of using Chlorine in water sterilisation?

Answer 18

kills potentially harmful microorganisms stopping disease

Question 19

What is a risk of using Chlorine in water sterilisation?

Answer 19

• Cl2 gas is toxic
• can increase risk of cancer if react with hydrocarbons
• can cause allergic reactions

Question 20

Give the equation showing the reaction of chlorine with cold, dilute sodium hydroxide

Answer 20

Cl2 + 2NaOH -> NaClO + NaCl + H2O

Question 21

What is a use of NaClO?

Answer 21

active ingredient in household bleach