Group 7 The Halogens Flashcards
Colour of fluorine + state
Pale yellow
Gas
Chlorine colour + state
Pale green gas
Bromine colour and state
Brown -orange
Liquid
Iodine colour and state
Grey
Solid
Trend in boilings points group 7
Increase down the group
Increase Van Der waals due to increasing size and relative mass of atoms
Trend in electronegativity group 7
This decreases going down the group
As the atoms get larger the distance between positive nucleus and bonding electron increases + more shielding
Displacement rule in halogens
A more reactive halogen will displace a less reactive halogen
What colour is iodine solution
Brown
Standard equation of halogens displacing each other half/ ionic equation
X2 + 2Y- —> 2X- + Y2
How is bleach made which reaction
Disproportionating reaction
Equation for making bleach
2NaOH + Cl2 —> NaClO + NaCl + H2O
Uses of bleach
Cleaning agents
Treating water
Bleaching fabrics
What happens in a disproportionation reaction w chlorine
The chlorine is reduced and oxidised simultaneously
Why is chlorine added to water
To kill bacteria
Reaction when water is added to chlorine
H2O + Cl2 —> 2H+ + Cl- + ClO-
Reaction when chlorine is added to water but in sunlight ionic
2H2O + Cl2 —> 4H+ + 2Cl- + O2
Advantages of chlorinating drinking water x4
Destroys microorganisms that causes diseases
Long lasting so reduces bacteria build up
Reduces the growth of algae
Not doing it can lead to cholera epidemic
Disadvantages of chlorinating drinking water x3
Chlorine gas is toxic
Liquid chlorine causes chemical burns
Chlorine could react with organic compounds to make chloroalkanes. These can cause cancer.
Are halides oxidising or reducing agents
Reducing agents
Trend in reducing ability of halides review
Increase going down
They are reducing agents so oxides themselves so they lose electrons
Going down distance between outer electron and nucleus increases and more shielding so attraction is weaker.
Test for halide ions
1) add dilute nitric acid to remove the any ions that could give false results
2) add silver nitrate
3) further test with ammonia
Chloride ions form what colour precipitate
White
Bromine produce what coloured ions..
Cream
Iodine produce what coloured ions
Yellow
Half equation standard for halide test with silver nitrate
Ag+(aq) + X-(aq) —> AgX(s)
Cl- white precipitate with ammonia observation
Dissolves in dilute ammonia
I- yellow precipitate with ammonia observation
Insoluble in concentrated ammonia
Br- cream precipitate with ammonia observation
Insoluble in concentrated ammonia
How to test for group 2 ions
Flame test
Dip wire in hydrochloric acid
Place loop into blue flame
What colour calcium on flame test
Dark red