ES

Question 1

Appearance of the halogens at room temperature

Answer 1

F2: pale yellow gas
Cl2: pale green gas
Br2: red-brown volatile liquid
I2: grey solid, sublimes to a purple vapour on heating.

Question 2

Volatility trend in the halogens down the group and why

Answer 2

volatility decreases because the halogen atoms increase in size and have more electrons so stronger ID-ID can form

Question 3

Halogens in aqueous solution/ polar solvent

Answer 3

low solubility because halogen molecules are covalent and non-polar, only weak ID-ID could form.
Cl2: pale yellow
Br2: yellow-orange
I2: brown

Question 4

Halogens in organic solvent/ non-polar solvent

Answer 4

High solubility because both the solvent and solute are non-polar and ID-ID can form.
Cl2: pale yellow
Br2: orange-red
I: pink-violet

Question 5

Reactivity trend down group 7 - the halogens

Answer 5

reactivity decreases down the group. Halogen atoms react by gaining 1 electron in their outer shell to form a halide ion. Down the group, atomic radius increases so the valence electrons and outer shell are further from the nucleus and there is greater shielding. The attraction of the nucleus is les strong at the outer shell so an eletra electron is attracted and a halide ion formed less easily.

Question 6

trend in oxidising strength of halogens down the group

Answer 6

oxidising strength decreases down the group

Question 7

trend in reducing strength of halide ions down the group

Answer 7

reducing strength increases down the group

Question 8

A more reactive halogen can..

Answer 8

displace a les reactive halide in a solution of its salt.

Question 9

Thermal stability of hydrogen halides - trend down the group and why

Answer 9

decreases down the group. the size of the halogen atom increases so bnding electrons are further from the nucleus ad the bond length is greater. The bonding electrons are less strongly attracted to the halogen atom and the bond is more easily broken.
Thermal decomposition produces hydrogen and the halogen element.

Question 10

How can hydrogen halides be formed?

Answer 10

by reacting a solid ionic halide (e.g. sodium halide) with concentrated phosphoric acid.

Question 11

Reaction of hydrogen halides with ammonia

Answer 11

white fumes of ammonium halide form.

NH3 (g) + HX (g) => NH4X (s)

Question 12

Reaction of hydrogen halides with sulfuric acid

Answer 12

HF and HCl do not react - the halide ion is not a strong enough reducing agent.
HBr: H2SO4 is reduced to SO2
HI: H2SO4 is reduced to H2S

Question 13

why can’t sulfuric acid be used to produce hydrogen halides from their sodium salts?

Answer 13

Because sulfuric acid is an oxidising agent

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Question 14

In which states must ionic substances be for electrolysis to work ad why?

Answer 14

molten/ in solution, as the ions are free to move and carry the electric current.

Question 15

What occurs at the anode in electrolysis?

Answer 15

oxidation

Question 16

What occurs at the cathode in electrolysis?

Answer 16

reduction

Question 17

What is oxidation? (4)

Answer 17

• loss of electrons
• gain of oxygen
• loss of hydrogen
• increase in oxidation number

Question 18

What is reduction? (4)

Answer 18

• gain of electrons
• loss of oxygen
• gain of hydrogen
• decrease in oxidation number

Question 19

Charges of electrodes in electrolysis

Answer 19

+ anode

- cathode

Question 20

Reduction of water equation

Answer 20

4H2O + 4e- => 2H2 + 4OH-

Question 21

Oxidation of water equation

Answer 21

2H2O => O2 + 4H+ + 4e-

Question 22

What is produced in the electrolysis of a molten salt? (and how)

Answer 22

anode - non-metal ions are oxidised and non-metal is formed

cathode - metal ions are reduced and metal is plated

Question 23

Electrolysis of aqueous solution - produced at the anode

Answer 23

• if halide ions are present, halogen is formed.

- if any other non-metal ions are present, oxygen is formed because water is oxidised

Question 24

Electrolysis of aqueous solution - produced at the cathode

Answer 24

• group 1/ 2/ aluminium: H2 gas is formed as water is reduced.
• other less reactive metals are reduced and plated on the cathode.

Question 25

electrolysis of aqueous solutions - reactive anode

Answer 25

if the metal forming the anode is the same as the metal ions in solution, metal ions can be made as metal atoms are oxidised at the anode. These ions enter the slution and areattracted to the cathode, where they are reduced and plated.
The anode loses mass, the cathode gains mass and the concentration of the solution remains the same because mass loss and gain occur at the same rate.

Question 26

Oxidation states of oxygen

Answer 26

-2, except in peroxides, fluorides and O2.

Question 27

oxidation states of hydrogen

Answer 27

+1, except in metal hydrides (-1) and H2

Question 28

what do redox reactions involve?

Answer 28

transfer of electrons

Question 29

What is formed when silver ions and halide ions react?

Answer 29

silver halide ppt
Cl - white
Br - cream
I - pale yellow
AgF - no ppt as soluble.

Question 30

Silver halide ppts and ammonia

Answer 30

used to distinguish between precipitates
AgCl - soluble in dilute ammonia solution
AgBr - soluble in concentrated ammonia solution
AgI - insoluble, even in concentrated ammonia solution

Question 31

Features o a dynamic equilibrium (5)

Answer 31

• reversible reaction
• closed system
• rates of forwards and reerse reactions are the same
• concentrations of products and reactants remain constant
• dynamic as both the forwards and reverse reactions are still occuring.

Question 32

Kc»1

Answer 32

Kc»1 (>10^10) - equilibrium lies far to the right, the concentration of products is much greater than the concentration of reactants.

Question 33

Kc«1

Answer 33

<10^-10: equilibrium lies far to the left, the concentration of reactants is much greater than the concentration of products.