terr123_78787
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#1
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#1
a scientist adds a solution of bromine in an organic solvent to two test tubes. the scientist adds aqueous sodium chloride to one test tube, and aqueous sodium iodide to the other test tube.

the student shakes the mixtures, allows then to settle and records the colour of the organic layer in each mixture.

results:

SODIUM HALIDE AND COLOUR OF ORGANIC LAYER:

sodium chloride- organe
sodium iodide- violet

explain how the students results provides evidence for the trend in reactivity of the halogens down group 17(7) and write and ionic equation for any reaction that takes place.

use your chemical knowledge to explain the trend in reactivity

can someone pls help me with this question
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charco
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#2
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(Original post by terr123_78787)
a scientist adds a solution of bromine in an organic solvent to two test tubes. the scientist adds aqueous sodium chloride to one test tube, and aqueous sodium iodide to the other test tube.

the student shakes the mixtures, allows then to settle and records the colour of the organic layer in each mixture.

results:

SODIUM HALIDE AND COLOUR OF ORGANIC LAYER:

sodium chloride- organe
sodium iodide- violet

explain how the students results provides evidence for the trend in reactivity of the halogens down group 17(7) and write and ionic equation for any reaction that takes place.

use your chemical knowledge to explain the trend in reactivity

can someone pls help me with this question
Bromine will displace iodine from iodide ions but not react with chloride ions.
The organic layer dissolves the halogen and shows its molecular colour, orange for bromine and violet for iodine.
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terr123_78787
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#3
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(Original post by charco)
Bromine will displace iodine from iodide ions but not react with chloride ions.
The organic layer dissolves the halogen and shows its molecular colour, orange for bromine and violet for iodine.
are these ionic equations correct?

2NaCl- (aq) + Br2 (aq) ---> 2Br- (aq) + NaCl2 (aq)

2NaI- (aq) + Br2(aq) ---> 2Br (aq) + NaI2 (aq)

and then this is what i thought the answer would be:

as the halogens react by gaining an electron in their outer shell- this means they are reduced. when halogens are reduced halide ions form. as the halogens are reduced they oxidise another substance- they are oxidising agents. As you go down the group, the reactivity decreases. the atomic radius increases as you go down the grouo so the outer electrons are further from the nucleus. the outer electrons are also shielded more from the attraction of the positive nucleus as there are more inner electrons. this makes it harder for larger atoms to attract the electron needed to form an ion despite the increases charge on the nucleus so larger atoms are less reactive. as halogens become less oxidising as you go down the group, they get less reactive.

more reactive halogens will oxidise and displace the halide ions of less reactive halogens. as the reactivity decreases down the group a halogen will displace a halide from solution if the halide if the halide is below it in the periodic table. In this case, bromine will displace iodine from iodide ions but not react with chloride ions and the organic layer dissolves the halogen and shows its molecular colour, orange for bromine and violet for iodine.

its a five marker question
how many marks would you roughly give this and do u think i have left anything out or is there anything i need to improve etc
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charco
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#4
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(Original post by terr123_78787)
are these ionic equations correct?

2NaCl- (aq) + Br2 (aq) ---> 2Br- (aq) + NaCl2 (aq)

2NaI- (aq) + Br2(aq) ---> 2Br (aq) + NaI2 (aq)
These are incorrect.

You never put charges onto compounds
The formula of NaCl is errr NaCl
The formula of NaI is errr NaI
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terr123_78787
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#5
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(Original post by charco)
These are incorrect.

You never put charges onto compounds
The formula of NaCl is errr NaCl
The formula of NaI is errr NaI
okay is it like this:

full equation:

Br2 (aq) + 2NaCl (aq) ---> 2NaBr (aq) + Cl2 (aq)

ionic equation:

Br2 + 2Cl- ----> 2Br- + Cl2

full equation:

Br2 + 2NaI ---> 2NaBr + I2

Ionic equation:

Br2 + 2I- ----> 2Br- + I2

this??
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charco
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(Original post by terr123_78787)
okay is it like this:

full equation:

Br2 (aq) + 2NaCl (aq) ---> 2NaBr (aq) + Cl2 (aq)

ionic equation:

Br2 + 2Cl- ----> 2Br- + Cl2

full equation:

Br2 + 2NaI ---> 2NaBr + I2

Ionic equation:

Br2 + 2I- ----> 2Br- + I2

this??
The equations highlighted in red do not happen because chlorine is a better oxidising agent than bromine...
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terr123_78787
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#7
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(Original post by charco)
The equations highlighted in red do not happen because chlorine is a better oxidising agent than bromine...
the question asks for the ionic equation of the reactions? so im confused what the ionic equation would be then?
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charco
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(Original post by terr123_78787)
the question asks for the ionic equation of the reactions? so im confused what the ionic equation would be then?
If there is no reaction there is no equation!
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terr123_78787
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#9
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#9
(Original post by charco)
If there is no reaction there is no equation!
so is this right?? how many marks would you give me out of five?

full equation:

Br2 + 2NaI ---> 2NaBr + I2

Ionic equation:

Br2 + 2I- ----> 2Br- + I2


as the halogens react by gaining an electron in their outer shell- this means they are reduced. when halogens are reduced halide ions form. as the halogens are reduced they oxidise another substance- they are oxidising agents. As you go down the group, the reactivity decreases. the atomic radius increases as you go down the grouo so the outer electrons are further from the nucleus. the outer electrons are also shielded more from the attraction of the positive nucleus as there are more inner electrons. this makes it harder for larger atoms to attract the electron needed to form an ion despite the increases charge on the nucleus so larger atoms are less reactive. as halogens become less oxidising as you go down the group, they get less reactive.

more reactive halogens will oxidise and displace the halide ions of less reactive halogens. as the reactivity decreases down the group a halogen will displace a halide from solution if the halide if the halide is below it in the periodic table. In this case, bromine will displace iodine from iodide ions but not react with chloride ions and the organic layer dissolves the halogen and shows its molecular colour, orange for bromine and violet for iodine.
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charco
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#10
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#10
(Original post by terr123_78787)
so is this right?? how many marks would you give me out of five?

full equation:

Br2 + 2NaI ---> 2NaBr + I2

Ionic equation:

Br2 + 2I- ----> 2Br- + I2


as the halogens react by gaining an electron in their outer shell- this means they are reduced. when halogens are reduced halide ions form. as the halogens are reduced they oxidise another substance- they are oxidising agents. As you go down the group, the reactivity decreases. the atomic radius increases as you go down the grouo so the outer electrons are further from the nucleus. the outer electrons are also shielded more from the attraction of the positive nucleus as there are more inner electrons. this makes it harder for larger atoms to attract the electron needed to form an ion despite the increases charge on the nucleus so larger atoms are less reactive. as halogens become less oxidising as you go down the group, they get less reactive.

more reactive halogens will oxidise and displace the halide ions of less reactive halogens. as the reactivity decreases down the group a halogen will displace a halide from solution if the halide if the halide is below it in the periodic table. In this case, bromine will displace iodine from iodide ions but not react with chloride ions and the organic layer dissolves the halogen and shows its molecular colour, orange for bromine and violet for iodine.
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