ES 1- The Halogens

Question 1

What kind of ions do all group 7 elements form?

Answer 1

-1 ions (gain 1 electron)

Question 2

Are halogens oxidising or reducing agents?

Answer 2

Oxidising agents; they are reduced by gaining 1 electron

Question 3

Halogens are reduced to…

Answer 3

Halides

Question 4

Halogens occur as diatomic molecules. What does this mean?

Answer 4

2 atoms are joined by a single covalent bond

E.g. Cl2, F2

Question 5

Does mp and bp increase or decrease down group 7? And why

Answer 5

• increase
• size of molecules increase, more electrons, stronger Van Der Waals
• more energy needed to break intermolecular forces (covalent bond is NOT broken)

Question 6

Why does volatility decrease down group 7?

Answer 6

Larger the molecule, more energy needed to change physical state

Question 7

What is volatility?

Answer 7

How easily a substance evaporates

Question 8

Is there a trend in solubility of group 7 elements in WATER?

Answer 8

No trend

Question 9

Is there a trend in solubility of group 7 elements in ORGANIC SOLVENTS?

Answer 9

Yes, solubility increases down group

Question 10

Does reactivity increase or decrease down group 7? And why

Answer 10

Decreases

- atomic radius increases, electron shielding increases, nuclear attraction decreases

Question 11

What does fluorine look like?

Answer 11

Pale yellow gas

Question 12

What does chlorine look like?

Answer 12

Pale green gas

Question 13

What does bromine look like?

Answer 13

Orange liquid

Question 14

What does iodine look like?

Answer 14

Shiny grey solid, sublimes to violet gas

Question 15

A halogen is dissolved in water and is brown, what element is it?

Answer 15

Iodine

Question 16

Give colours of chlorine bromine and iodine dissolved in cyclohexane

Answer 16

Chlorine: pale green
Bromine: orange/brown
Iodine: violet

Question 17

What is formed when halides react with aqueous silver ions?

Answer 17

A precipitate is formed

Question 18

Give general equation for Halide + aqueous silver ions

Answer 18

Ag+(aq) + X-(aq) AgX(s)

Question 19

Give a test for halide ions, and results

Answer 19

1. Add nitric acid and silver nitrate ions to sample
2. Precipitate should form, white=Cl, cream=Br, pale yellow=I
3. Add dilute ammonia, if precipitate dissolves=AgCl
4. If not, add conc ammonia, if dissolves=AgBr
5. If precipitate not dissolved=AgI

Question 20

Which is the strongest oxidising agent, Cl or I?

Answer 20

Cl, oxidising ability decreases down group 7

Question 21

What is a spectator ion?

Answer 21

Ions that are unchanged in a reaction (therefore left out of ionic equations)

Question 22

Give ionic equation of chlorine and iodide ions

Answer 22

Cl2 + I- 2Cl- + I2

Question 23

In reactions between halogens and halides, which will become ions?

Answer 23

Strongest oxidising agent

Question 24

What do half equations show?

Answer 24

Oxidation and reduction of species in an equation

Question 25

Will there be a reaction between Br2 and I-? If so give colour changes (in cyclohexane)

Answer 25

Yes; Br2 is stronger oxidising agent than I, will become ions
Colour changes from orange to violet

Question 26

Will there be a reaction between I2 and Cl-? If so give colour changes (in cyclohexane)

Answer 26

No reaction, chloride is stronger oxidising agents, and is already ions

Question 27

Why is the reaction between a halogen and a halide called a ‘displacement reaction’?

Answer 27

Halogen displaces (pushes out) a less reactive halogen from a compound