ES2 (The Halogens)

Question 1

what is the state of fluorine, chlorine, bromine and iodine at room temperature?

Answer 1

fluorine is a pale yellow gas
chlorine green gas
bromine dark red liquid
iodine shiny black solid

Question 2

what colours do each of the halogens give when dissolved in water?

Answer 2

fluorine reacts, chlorine gives a place green colour, bromine gives a red brown colour, iodine gives a brown colour

Question 3

what colours do they give off when dissolved in hexane?

Answer 3

chlorine gives pale green still, bromine red, iodine violet

Question 4

why do intermolecular bonds get stronger as you go down the group?

Answer 4

molecules get bigger because there are more electrons

Question 5

why does reactivity decrease as you go down the group?

Answer 5

each successive halogen has one more complete electron shell than the previous so there’s greater distance between them which means a weaker nuclear attraction so they gain an electron less readily, decreasing reactivity

Question 6

what will a more reactive halogen do?

Answer 6

oxidise the halide ions of a less reactive one which isn’t reversible

Question 7

what colour is silver chloride, bromide and iodide?

Answer 7

white, cream and yellow

Question 8

describe the properties of the halogens going down the group

Answer 8

darker in colour, melting and boiling point increase, they change from gas to liquid to solid at room temperature and they become less volatile

Question 9

describe 3 points to oxidation

Answer 9

a gain of oxygen, loss of electrons and an increase in oxidation state

Question 10

describe 3 points to reduction

Answer 10

a loss of oxygen, a gain of electrons, and a decrease in oxidation states

Question 11

list the ox. states for fl, o, cl, br, i, h, G1, G2, and Al

Answer 11

-1, -2, -1, -1, -1, +1, +1,

Question 12

what is the equation for excess iodide ions being added to chlorate ions

Answer 12

CLO- + 2I- + 2H+ —> I2 + CL- + H2O. brown

Question 13

what is the equation for iodine produced after being titrated with S2O3,2-

Answer 13

S2O3,2- + I2 —-> 2I- + S4O6 brown to pale yellow

Question 14

when is the end point in the bleach titration

Answer 14

when the final trace of blue/black colour is no longer visible

Question 15

what is the percentage for atom economy

Answer 15

rfm of the desired products divided by the rfm of all reactants used * 100

Question 16

describe the trends of oxidising and reducing agents in the halogens

Answer 16

as you go down the group the strength of reducing agents increases and that of oxidising agents decreases

Question 17

what does a change in ox state indicate

Answer 17

an increase means a reducing agent, decrease means it has been reduced

Question 18

describe the reaction to produce pure hydrogen bro,ide

Answer 18

sodium bromide reacts with concentrated sulfuric acid to make HBr
the bromide ions produced are strong enough reducing agents to reduce the sulfuric acid to sulfur dioxide
this is not a good way as the HBr will not be pure

Question 19

describe the reaction of sodium idiotie to make hydrogen iodide

Answer 19

first reacts with concentrated sulfuric acid to make HI
the iodide ions produced are even stronger reducing agents than bromide so sulfuric acid is reduced further to make hydrogen sulfide this won’t be pure

Question 20

what are the characteristics of hydrogen iodide and hydrogen sulfide

Answer 20

HI has white fumes
H2S has a rotten egg smell

Question 21

why is phosphoric acid used to make pure hydrogen halodes

Answer 21

because it won’t be reduced and so a pure HH can be collected

Question 22

describe the trend of thermal stability in g7

Answer 22

decreases down the group, due to bond strength between the H and halogen decreases so less energy is needed to break the bonds

Question 23

what happens when the halides are heated in a lab

Answer 23

HF and HCl are not broken down
HBr some brown bromine vapour is made
HI large amounts of purple gaseous iodide is produced

Question 24

describe the reactions of ammonia

Answer 24

they all make salts
if a glass rod is dipped in concentrated ammonia solution then placed in the hydrogen halide a white cloud of ammonium halide is made

Question 25

what is are the reactions with sulfuric acid

Answer 25

HF and HCl don’t react
HBr makes sulfur dioxide
HI makes hydrogen sulfide