Elements From The Sea

Question 1

How do you calculate atom economy?

Answer 1

Mr of useful products/ total Mr of products x 100

Question 2

What forms at the anode if the solution contains halide ions?

Answer 2

Halogen

Question 3

What happens at the anode if it’s a sulphate or nitrate?

Answer 3

Oxygen is produced

Question 4

What happens at the anode if its a hydroxide?

Answer 4

Oxygen produced from OH-

Question 5

What is formed at the cathode if it is a group 1/2 metal or aluminium?

Answer 5

Hydrogen gas produced from water

Question 6

What is produced at cathode if it’s a metal not in group 1 or 2 or aluminium?

Answer 6

Metal produced

Question 7

What is produced at the cathode if it’s an acid?

Answer 7

Hydrogen from H+ ions

Question 8

Define oxidation

Answer 8

Loss of electrons

Question 9

Define reduction

Answer 9

Gain of electrons

Question 10

What are the two steps of a iodine-thiosulfate titration?

Answer 10

Use an oxidising agent to oxidise as much iodine as possible
- excess acidic potassium iodide

Titration iodine with sodium thiosulfste to calculate moles of iodine produced

then calculate concentration of oxidising agent from this

Question 11

What is the appearance of fluorine at room temp?

Answer 11

Pale yellow gas

Question 12

What is the appearance of chlorine at room temp?

Answer 12

yellow-Green gas

Question 13

What is the appearance of bromine at room temp?

Answer 13

Dark red volatile liquid

Question 14

What is the appearance of iodine at room temp?

Answer 14

Shiny black solid

Question 15

What is the trend in volatility of halogens? why?

Answer 15

Decrease down group

the strength of the IDID intermolecular bonds inceeases down group due to more electrons

Question 16

What is the trend in solubility of halogens in water?

Answer 16

Decreases in solubility down group

Question 17

Colour of chlorine in water?

Answer 17

Pale green

Question 18

Colour of bromine in water?

Answer 18

yellow/Orange

Question 19

Colour of iodine in water?

Answer 19

Brown

Question 20

Are halogens more or less soluble in organic solvents than water?

Answer 20

More

Question 21

Colour of chlorine in hexane?

Answer 21

Pale green

Question 22

Colour of bromine in hexane?

Answer 22

Orange/brown

Question 23

Colour of iodine in hexane?

Answer 23

Violet

Question 24

Trend in reactivity of halogens? And 2 reasons?

Answer 24

Decrease in reactivity

Less shielding at top
So stronger attraction to extra electrons from nucleus

Question 25

How do you prepare HCl?

Answer 25

Add sulfuric acid or phosphoric acid to chlorine ions

Question 26

How do you prepare HBr and HI?

Answer 26

Add concentrated phosphoric acid to NaI/Br

Question 27

Trend in thermal stability of hydrogen halides

Answer 27

Decreases down group as bond strength decreases due to sheilding

Question 28

Acidity of halogen halides?

Answer 28

All strong acids apart from HF which is a weak acid

Question 29

Reaction of hydrogen halides with ammonia?

Answer 29

Produce ammonium halide= white fumes

Question 30

Reactions of hydrogen halides with sulfuric acid?

Answer 30

HCl- no reaction HBr- SO2 HI- H2S

Question 31

what are properties of dynamic equilibrium?

Answer 31

must be a closed system froward reaction is occuring at the same rate as back reaction concentrations are constant

Question 32

``` Kc>>1 kc> 1 kc=1 kc<1 kc<<1 ```

Answer 32

``` equilibrium lies far to the right equilibrium lies to right equilibrium is in he centre equilibrium is to the left equilibrium lies far to the left ```

Question 33

effect on Kc of pressure temperature concentration of a reactant

Answer 33

changes Kc changes Kc no effect on Kc

Question 34

why doesnt changing the concentration of a reactant change the Kc

Answer 34

if a concentration term on the top becomes larger one on the bottom must also become larger to keep Kc constant so equilibrium position moves to left etc

Question 35

what are the uses of chlorine?

Answer 35

sterilising water by killing bacteria bleaching

Question 36

what are the risks associated with storing and transporting chlorine?

Answer 36

it is toxic and corrosive - keep away from eyes and skin and when breathed in irritates respiratory system is an oxidising agent so needs to be kept away from flamable materials needs to be stored under pressure in small cylinders

Question 37

what is the solubility of Ag Cl AgBr AgI with ammonia?

Answer 37

soluble in dilute and concentrated ammonia soluble in concentrated ammonia ppt does not dissolve