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urban_flavaz
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#1
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#1
hi can some help me on the following:

1) explain the term displacement and give observations and equations for each halogen with each halide ions.

2) Illustrate the above with particular referenece to the extraction of bromine from sea - water.

3) Explain the pattern and the reasons for the relative strengths of the elements as oxidising agents particularly with reference to (1) above.

thank u, all help much appreciated
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swifty
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Bromine from sea water-
Cl2 + 2Br- -> Br2 + 2Cl-

Chlorine will oxidise bromide ions to bromine, iodide ions to iodine.
Bromine will oxidise iodide ions to iodine.
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oxymoron
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Something is oxidised when it loses electrons. So strong oxidising agents need to have a strong affinity for electrons.

The halogens all have 7 electrons in their outer shell so want to accept one electron to fill the shell and be stablised.

Chlorine is smaller than bromine, so it's outer electrons are closer to the nucleus, so it accepts an electron more easily as it is more strongly attracted by the postive nucleus. Therefore as you go down the group, the halogens attract electrons less strongly and become worse oxidising agents.
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Christophicus
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(Original post by urban_flavaz)
hi can some help me on the following:

1) explain the term displacement and give observations and equations for each halogen with each halide ions.
2) Illustrate the above with particular referenece to the extraction of bromine from sea - water.

3) Explain the pattern and the reasons for the relative strengths of the elements as oxidising agents particularly with reference to (1) above.

thank u, all help much appreciated
Cl2 + 2Br- --> 2Cl+ Br2
Solution turns orange/brown.

Cl2 + 2I- --> 2Cl + I2
The iodide solution turns dark brown with a black precipitate.

Chlorine is the strongest oxidising agent and can therefore oxidise both bromide and iodide ions.

Br2 + 2I- --> 2Br- + I2
The iodide solution turns dark brown with a black precipitate.

Bromide can only oxidise iodide ions.

Iodine is the weakest oxidising agent and cannot oxidise bromide or chloride ions.
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BCHL85
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(Original post by oxymoron)
Something is oxidised when it loses electrons. So strong oxidising agents need to have a strong affinity for electrons.

The halogens all have 7 electrons in their outer shell so want to accept one electron to fill the shell and be stablised.

Chlorine is smaller than bromine, so it's outer electrons are closer to the nucleus, so it accepts an electron more easily as it is more strongly attracted by the postive nucleus. Therefore as you go down the group, the halogens attract electrons less strongly and become worse oxidising agents.
It means electronegativity of Chlorine > that of Bromine > that of Iodine
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