3.1.3 Groups 17: The Halogens Flashcards Preview

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Flashcards in 3.1.3 Groups 17: The Halogens Deck (18)
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1

What are the main two properties of halogens?

> low melting and boiling points
> they exist as diatomic molecules, x^2 where x represents the halogen

2

What is the trend in boiling points of halogens?

> Moving down the groups, the boiling point increases
> Number of electrons increase
> Which increases the strength of London forces
> More energy required to break the intermolecular forces

3

Describe the reactivity of the halogens

Halogens are very reactive and highly electronegative

4

Describe halogens as oxidising agens

They are very good at attracting and capturing electrons which means the are strong oxidising agents

5

What happens to halogens during reactions

Each atom gains an electron to form 1- ions known as halide ions

6

What is the trend of the reactivity and oxidising power of halogens?

It decreases as you move down the group, this is because:
> Atomic radius increases
> Electron shielding increases
> The ability to gain an electron in the p sub-shell to form an 1- ions decreases

7

Definition of displacement reaction

A more reactive halogen will oxidise and displace a halide of a less reactive halogen

8

Cl2 colour in water & colour in cyclohexane

Pale Green in both

9

Br2 colour in water & colour in cyclohexane

Orange in both

10

l2 colour in water & colour in cyclohexane

brown in water and violet in cyclohexane

11

Show the oxidation of chlorine:
Cl2 (AQ) + 2BR- (AQ) -->

Cl2 (AQ) + 2BR- (AQ) --> 2Cl-(AQ) + Br2 (AQ)

12

Show the oxidation of chlorine:
Cl2 (AQ) + 2I- (AQ) -->

Cl2 (AQ) + 2I- (AQ) --> 2Cl-(AQ) + I2 (AQ)

13

Show the oxidation of Bromine:
Br2 (AQ) + 2I-(AQ) -->

Br2 (AQ) + 2I-(AQ) --> 2Br- (AQ) + I2(AQ)

14

Definition of Disproportionation

Its the oxidation and reduction of the same element in a redox reaction

15

Uses & risks of reacting Cl2 + H2O

> Cl2 kills bacteria, making water safer to drink (purification of water)
> Hazard of toxic chlorine gas

16

Purification of water:
Cl2 (AQ) + H2O (L) -->

Cl2 (AQ) + H2) (L) --> HClO (AQ) + HCL (AQ)

17

uses of reacting Cl2 + NaOH ( sodium hydroxide)

Bleach formation

18

Bleach formation:
Cl2 (AQ) + 2NaOH (AQ) -->

Cl2 (AQ) + 2NaOH (AQ) --> NaCl (AQ) + NaClO (AQ) + H2O (L)