How to approach this displacement/group 7, A-Level question?

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swaus
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#1
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#1
"Describe how displacement reactions can be used to show the different reactivies of chlorine, bromine and iodine."
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username3249896
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#2
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Consider the reactions when the halogen is added to solutions of halide

e.g
for chlorine, react it with KBr, KI (i.e Br- and I-)

for bromine, react with it KCl, KI

for iodine, react it with KCl, KBr

then give the results, and state what conclusion can be taken from the results
probably also useful to give the equation for the displacement reactions occurring & perhaps observations too
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swaus
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(Original post by BobbJo)
Consider the reactions when the halogen is added to solutions of halide

e.g
for chlorine, react it with KBr, KI (i.e Br- and I-)

for bromine, react with it KCl, KI

for iodine, react it with KCl, KBr

then give the results, and state what conclusion can be taken from the results
probably also useful to give the equation for the displacement reactions occurring & perhaps observations too
Cl2 + 2I- >> i2 + 2Cl-
Cl2 + 2Br- >> Br2 +2Cl-
Br2 + 2Cl- >> Cl2 + 2Br-
Br2 + 2I- >> I2 + Br-

The ionic equations of reacting halogens as cations and in their natural states show us that, going up the group, elements become better oxidising agents as the oxidation number increases, making them more reactive. Colour changes after dissolving soluutions in cyclohexane, are indicative of reactivity as it shows us the halogen present that has displaced the less reactive one (iodine will be purple, bromine a strong orange and chlorine a pale green).

Would this answer get 4/4 marks?
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Pigster
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#4
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(Original post by swaus)
Br2 + 2Cl- >> Cl2 + 2Br-
Would this answer get 4/4 marks?
Since this reaction doesn't take place, then you won't get 4/4. The explanation wouldn't get any marks on an OCR A paper.
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swaus
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(Original post by Pigster)
Since this reaction doesn't take place, then you won't get 4/4. The explanation wouldn't get any marks on an OCR A paper.
So, do I write about a smaller atomic radius, outweights the lower positive charge, and weaker shielding effect makes gaining an electron easier up the group?
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Pigster
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#6
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(Original post by swaus)
So, do I write about a smaller atomic radius, outweights the lower positive charge, and weaker shielding effect makes gaining an electron easier up the group?
If you are doing OCR A, that would do nicely.
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