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Redox half reactions question

2NaOH + Cl2 ----> NaCl + NaOCl + H2O Clearly identify the chemical species that are oxidised and those that are reduced and write oxidation and reduction half reactions.

I know chlorine is both oxidized and reduced but could someone help me with the half reactions please?
(edited 7 years ago)
Reply 1
Avatar for alow
alow
19
"Undergraduate"
Reply 2
Avatar for Pigster
Pigster
20
Cl2 -> Cl-

AND

Cl2 -> ClO-

You surely can do the rest.
Reply 3
Avatar for Pigster
Pigster
20
Original post by alow
"Undergraduate"


I fell your pain. I wouldn't have know which side of the under/post-graduate divide this would fall, either.
Reply 4
Avatar for elef95
elef95
OP
7
Cl2 + 2e- --> 2Cl-

Cl2 + 2e- --> 2ClO- where do you get the O to balance this?
Reply 5
Avatar for Pigster
Pigster
20
From water.

Which will also mean adding H+ ions.

Which might make you change your mind about the e-.
Reply 6
Avatar for elef95
elef95
OP
7
Original post by Pigster
From water.

Which will also mean adding H+ ions.

Which might make you change your mind about the e-.


Is the first one correct?

Cl2 + 2OH- --> 2ClO- + 2e- + 2H+
That isn't right is it?
Reply 7
Avatar for Pigster
Pigster
20
You can't have OH- on the left and H+ on the right.

The O in ClO- comes from water, not OH-.
Reply 8
Avatar for elef95
elef95
OP
7
Original post by Pigster
You can't have OH- on the left and H+ on the right.

The O in ClO- comes from water, not OH-.


I don't understand. Will you show me how to write them correctly?
Reply 9
Avatar for Pigster
Pigster
20
Cl2 -> ClO-

Cl2 -> 2ClO-

Cl2 + 2H2O -> 2ClO-

Cl2 + 2H2O -> 2ClO- + 4H+

Cl2 + 2H2O -> 2ClO- + 4H+ + 2e-
Reply 10
Avatar for elef95
elef95
OP
7
Original post by Pigster
Cl2 -> ClO-

Cl2 -> 2ClO-

Cl2 + 2H2O -> 2ClO-

Cl2 + 2H2O -> 2ClO- + 4H+

Cl2 + 2H2O -> 2ClO- + 4H+ + 2e-


Thank you!

H2O + Cl2 --> HCl + HOCl
Would these be the right half reactions for this reaction?

Cl2 + 2H+ + 2e- --> 2HCl

Cl2 + 2H2O --> 2HOCl + 2H+ +2e-
You wouldn't usually show them as acids in the half equation as they should be ionic equations, and the H+ on both sides would cancel.
Reply 12
Avatar for elef95
elef95
OP
7
Original post by Pigster
You wouldn't usually show them as acids in the half equation as they should be ionic equations, and the H+ on both sides would cancel.


How would you write them?
You've already done the Cl- one yourself, I have already done the ClO- one.
Reply 14
Avatar for elef95
elef95
OP
7
Cl2 + 2e- --> 2Cl-

Cl2 + 2H2O --> 2OCl + 4H+ + 2e-

Are these the correct ionic equations?
Apart from the charge missing, they look fine.
Reply 16
Avatar for elef95
elef95
OP
7
Original post by Pigster
Apart from the charge missing, they look fine.


Thanks! Last one.

F2 + 2KBr --> Br2 + 2KF

F2 + 2e- --> 2F-
2Br- --> Br2 + 2e-

That's it right?
Agreed.

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