Flashcards
Group 7, the Halogens
Cards in this deck (20)
- 1The HalogensPhysical Properties:
Physical appearances at room temperature
Size of Atoms
Electronegativity
Melting and Boiling Points - 2Physical appearances at room temperature...Flourine- Yellow Gas
Chlorine- Green Gas
Bromine- Brown/Red Liquid
Iodine- Black solid/Purple Gas - 3Size of Atom...The atomic radius gets bigger as we go down group 7 with FLUORINE having the smallest atomic radius and ASTATINE having the largest atomic radius
- 4Electronegativity...As we go up the group 7 halogens, the electronegativity of the elements increase. So, ASTATINE would not be as able to attract electrons towards itself across a covalent bond compared to a FLUORINE atom which can quite readily attract electrons towards itself across a covalent bond
- 5Melting and Boiling Points...Both the melting and boiling points increase as we go down the group 7 halogens. This is because LARGER ATOMS have more electrons and this makes VAN DER WAALS forces between molecules STRONGER. Halogens with LOWER boiling points are more VOLATILE (i.e CHLORINE GAS)
- 6The Chemical reactions of the halogens......Trends in oxidising ability
...Displacement Reactions - 7Trends in oxidising ability...Halogens generally react by GAINING electrons so they can become NEGATIVE IONS with charge of -1. The oxidising ability of the halogens INCREASE as we go up group 7
- 8Displacement Reactions...As we go up the group 7 halogens, reactivity increases and so, the ability of a halogen to displace another less-reactive halogens increases also.
i.e. chlorine + potassium bromide ==> potassium chloride + bromine
Cl2(aq) + 2KBr(aq) ==> 2KCl(aq) + Br2(aq)
The halide (in this case the Br) in the metal halide will get displaced by the more reactive halogen (so, the Cl2). - 9Reactions of halide ions......Halide ions as reducing agents
...The reactions of sodium halides with concentrated sulphuric acid
...Identifying metal halides with silver ions - 10Halide ions as reducing agents...As reducing agents, halide ions lose (or donate) electrons and become halogen molecules. The LARGER the halide ion, the more easily it loses an electron because of shielding
- 11The reactions of sodium halides with concentrated sulphuric acid...Sodium chloride (solid):
Drops of conc. H2SO4 are added to sodium chloride in a solid state. Observations- steamy hydrogen chloride fumes seen as well as the solid ppt of SODIUM HYDROGENSUPHATE.
This is an ACID-BASE reaction - 12The reactions of sodium halides with concentrated sulphuric acid (2)...Sodium Bromide:
Firstly, sodium hydrogensulphate and hydrogen bromide are produced in a similar acid-base reaction to the sodium chloride reaction. However unlike the last reaction, the bromide ions are strong enough reducing agents to reduce the sulphuric acid to sulphur dioxide. This is an exothermic redox reaction.
Observations- steamy fumes of hydrogen bromide and BROWN fumes of bromine as well as colourless sulphur dioxide. - 13The reactions of sodium halides with concentrated sulphuric acid (3)...Sodium Iodide (solid):
Hydrogen iodide is produced in an acid-base reaction, then the iodide ions are the better reducing agents compared to the bromide ions and so, they reduce the S in H2SO4. So sulphur dioxide, sulphur and hydrogen sulphide gases are produced.
Observations- some solid, yellow sulphur, steamy fumes of hydrogen iodide and black solid iodine. - 14Identifying metal halides with silver ions...(With the exception of fluorides), ALL METAL HALIDES REACT WITH SILVER IONS IN (aq) SOLUTION!
- 15Identifying metal halides with silver ions (2)...i.e. AgCl
(i) Ag+(aq) + Cl-(aq) ==> AgCl(s)
Any soluble silver salt + any soluble chloride gives a white silver chloride precipitate, that darkens in light.
(ii) Cl-(s) + H2SO4(l) ==> HSO4-(s) + HCl(g) ,
then Ag+(aq) + Cl-(aq) ==> AgCl(s) - 16Identifying metal halides with silver ions (3)...i.e. AgBr
(i) Ag+(aq) + Br-(aq) ==> AgBr(s)
Any soluble silver salt + any soluble bromide gives a cream silver bromide precipitate.
(ii) The bromide ion is oxidised to bromine and the sulphuric acid is reduced to sulphur dioxide. (Test for sulphur dioxide - potassium dichromate(VI) paper changes from orange to green) - 17Identifying metal halides with silver ions (4)...i.e AgI
(i) Ag+(aq) + I-(aq) ==> AgI(s) , any soluble silver salt + any soluble iodide ==> silver iodide precipitate,
(ii) iodide ion is oxidised to iodine and the sulphuric acid is reduced to 'rotten eggs' smelly hydrogen sulphide - 18Uses of Chlorines......Reaction with water
...Reaction with alkali - 19Reaction with water...i.e. chlorine reacting with water in a REVERSIBLE REACTION to form chloric(I) acid (HClO) and hydrochloric acid (HCL). It is a redox reaction but, the oxidation state of one of the chlorine atoms increases from 0 to +1, and other decreases from 0 to -1. This is called DISPROPORTIONATION!
Application- takes place when chlorine is used to purify water for drinking and in swimming baths.
Other halogens react in a similar fashion, just slower - 20Reaction with alkali...i.e. chlorine reacting with cold, dilute sodium hydroxide to form sodium chlorate(I), NaClO.
NaClO is an oxidising agent and is an active ingredient in household bleach. The reaction that takes place here is also disproportionate.
Other halogens behave in a similar fashion
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- AS/A2 Level Chemistry Unit 2 Flashcards on Group 7, the Halogens, created by Amar B. on 27/04/2015.
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- Amar B.
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