group 7 + chlorination

Question 1

What are the main properties of group 7 elements?

Answer 1

They are all very reactive non-metals.

Question 2

which elements are a gas at room temperature?

Answer 2

flourine, and chlrine.

Question 3

which elements are liquid at room temperature?

Answer 3

bromine.

Question 4

which elements are solid at room temperature?

Answer 4

iodine.

Question 5

describe the trend in electronegativity as we go down group 7.

Answer 5

Electronegativity decreases as we go down group 7.

This is because as we go down group 7, there are full shells of electrons. This mens that there is more shielding, and and also the atomic radius is bigger, which means that the shared electron pair is further away from the nucleus. these factors outweight the increase in nuclear charge. This means that the shared electron pair experiences less attraction towards the nucleus.

Question 6

describe the trend in boiling point of halogens.

Answer 6

as we go down group 7, the elements have more electrons, which means stronger wan der waals forces, which means that more energy is needed to overcome these factors.

Question 7

What is a displacement reaction?

Answer 7

when a more powerfull oxidising agent, or reducing agent, takes over a less powerfull one, we say it displaces it.

we call these tye of reactions, displacement reactions.

Question 8

describe the trend in oxidising ability as we go down group 7.

Answer 8

decreases as we go down group 7.

Question 9

describe the trend in reducing ability as we go down group 7.

Answer 9

increases as we go dow group 7.

Question 10

describe and show the reactions between NaF and NaCl, with H2SO4.

Answer 10

NaF+H2SO4—->NaHSO4+HF
NaCl+H2SO4—->NaHSO4+HCl

These arent strong eneough reducing agents. This means that they dont form redox reactions.

These are acid-base reactions.

Question 11

describe, and show the reaction between NaBr, and sulfuric acid. what colour change will you observe?

Answer 11

bromide ions, react with sulfuric acid, in both acid-base reactions, and a redox reaction.

acid-base: NaBr+H2SO4—->NaHSO4+HBr

redox: 2H+ + 2Br- + H2SO4—-> SO2+2H2O+Br2

sulfur has been oxidised from +6, to +4.

The Br2, will produce brown fumes.

Question 12

describe, and show the reaction, between NaI, and sulfuric acid. What colour changes will you observe?

Answer 12

Iodine ions, react with sulfuric acid, in both acid-base reactions, and redox reactions.

acid base: NaI+H2SO4—-> NaHSO4+ HI ( steamy fumes of hydrogen can be observed)

redox: 8H+ + 8I- + H2SO4—-> H2S+ 4H2O+4I2

we smell the sulfite gas (H2S), as rotten egs.

We can observe iodine as a black, or dark grey solid.

sulfur is being reduced from +6, to -2.

Question 13

Describe what colour each halide, will have, in contact with silver nitrate.

Answer 13

flourine: colourless
Chlorine: white precipitate
Bromine: cream - coloured precipitate
Iodine: yellow precipitate.

Question 14

Why do we need to add acid to our silver nitrate, when testing for halides.

Answer 14

Because we need to make sure that we remove any impurities, such as soluble hydroxides, or carbonates.

Question 15

show the equation, of chlorine reacting with water.
state what type of equation it is as well.

Answer 15

Cl2(0)+H20—->HCl(-1)+HClO(+1)

It is a disproportionation reaction, because chlorine is both oxidised and reduced.

Question 16

what does chloric acid dissociate into? and explain how this helps treat water supplies.

Answer 16

Chloric acid, dissociates into chlorate (I) ions.

These chlorate(I) ions, are oxidising agents, meaning that they are very toxic.

However, in small concentrations, they dont affect humans, however, they kill all bacteria.

This is good, because we can put it in our water supply, to kill all bacteria.

Question 17

explain how chlorine reacts with water in sunlight, and how this affects the water supply.

Answer 17

chlorine can react with water in a different way. This is through sunlight.