exam Flashcards
Properties of the halogens
- low solubulity in water
2. Disoolve easily in organic compounds like hexane
Colour and state at room temperature of fluorine
pale yellow gas
Colour and state at room temperature of chlorine
green gas
Colour and state at room temperature of bromine
red-brown liquid
Colour and state at room temperature of iodine
grey solid
Colour in water for chlorine
colourless
Colour in water for bromine
yellow/orange
Colour in water for iodine
brown
Colour in hexane for chlorine
colourless
Colour in hexane for bromine
orange red layer
Colour in hexane for iodine
pink violet
Trend in reactivity as you go down the groups of halgens
- Get less reactive down the group
- As you go down the group the atom becomes karger so the outer electrns are further away from the nucleus and they are shielded more fro the possitive attraction of the nucleus due to the inner elecectons
- tHis makes it harder for larger atoms to attract the elctron needed to form an ion
Trend in boiling and melting points as you go down the group halogens
- As you go down group 7 there is an increase in electron shells and electrons meaning that the london forces between the halogen moleucles get stronger
- The increase in london forces meansmore energy is required to break these intermoleuclar forces so the melting and boiling points increases
What happens to the thing that is displaced
oxidised
WHta happens to the thing that is doing the displacing
Reduced
Reaction between halogen and group 1 and 2 metals
They produce halide salts
WHta is a disproportionation reaction
When a substance is simuktaneously oxidised and reduced
Reaction between halogen and cold alkali
1, Disproportionation reaction
x2 + 2NaOH >NaOx + NaX + H20
ionic= x2 + 2OH- > OX- + X- + H20
Reaction between halogen and hot alkali
1, Disproportionation reaction
3x2 + 6NaOH >NaxO3 + 5NaX + 3H20
ionic= 3x2 + 6OH- > XO3- + 5X- +3 H20
Reaction between chlorine and sodium hydroxide
- Makes bleach (NaCLO)
2. 2NaOH +CL2 > NaCLO + NaCL + H2O
Reaction between chlorine and water ( 2 equations
- Disproportionation reaction
You get hydrochloric acid and hypochlorous acid
CL2 + H20 > HCL + HCLO
This is a reversible reaction
HCLO + H20 > CLO- + H3O+
Test for halogens
- Add dilute nitric acid
- Add silver nitrate solution
- A precipitate wil be formed of the silver halid3
Colour of silver precipitate of fluoride
no precipitate AgF is soluble
Colour of silver precipitate of chloride
White precipitate
Colour of silver precipitate of bromide
Cream precipitate
Colour of silver precipitate of iodide
yellow precipitate
AgCl when you add ammonia solution
precipitate dissolves in dilute ammonai solution to give a colourless solution
AgBr when you add ammonia solution
Precipitate remains unchanged if dilute amminia solution is added but will dissolve in concentarted ammonia solution to give a colourless solution
AgI when you add ammonia solution
Precipitate does not dissolve even in concentrated ammonia solution
What is the tests for sulfates
- Add dilute HCL followed by barium chloride solution
2. If a white precipitate of barium sulfate forms the compound contained sulfate
Wgat is the test for ammonium compounds
- Ammonia is alkaline so we use red litmus paper
- A dd sodium hydroxide to mystery substance
- Gently heat the mixture
- If damp red litmus paper turns blue ammonia present
