# Redox equation what has gone wrong?

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#1
The reduction of chlorate(V) ions, ClO3 - , to chlorine gas, Cl2. I have to construct a half equation for this.
My answer : 10e- + 2ClO3- + 6H+ --> Cl2 +6OH- I have checked this and the charges do balance..

ANSWER 2ClO3 - + 12H+ + 10e- -> Cl2 + 6H2O

The answer shows water is made but I thought OH- would, am I wrong. But if the charges are balanced then would it be okay? I don't know whether my equation makes sense...

Thanks
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#2
Help?
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4 years ago
#3
(Original post by coconut64)
The reduction of chlorate(V) ions, ClO3 - , to chlorine gas, Cl2. I have to construct a half equation for this.
My answer : 10e- + 2ClO3- + 6H+ --> Cl2 +6OH- I have checked this and the charges do balance..

ANSWER 2ClO3 - + 12H+ + 10e- -> Cl2 + 6H2O

The answer shows water is made but I thought OH- would, am I wrong. But if the charges are balanced then would it be okay? I don't know whether my equation makes sense...

Thanks
Does the question specify that it's being done under acidic conditions? If so, you can't add hydroxide ions as they will neutralise the H+ ions.

Can you put up the Oxidation half equation also?
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#4
(Original post by _NMcC_)
Does the question specify that it's being done under acidic conditions? If so, you can't add hydroxide ions as they will neutralise the H+ ions.
No, it is just asking to show an equation for it. It is not an exam question. My equation is balanced, so does it matter ?

Thanks
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4 years ago
#5
in acidic conditions hydroxide ions are never on either side of the equation
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#6
(Original post by _NMcC_)
Does the question specify that it's being done under acidic conditions? If so, you can't add hydroxide ions as they will neutralise the H+ ions.

Can you put up the Oxidation half equation also?

can't add hydroxide ions as they will neutralise the H+ ions. -> but if you take H2O2 as an example, there are both H+ and OH- in the equation
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4 years ago
#7
(Original post by coconut64)
No, it is just asking to show an equation for it. It is not an exam question. My equation is balanced, so does it matter ?

Thanks
It's probably not worth many marks anyway but unless it specifies or it's obvious that an alkaline solution is being formed. I usually always balance for acidic conditions.
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#8
(Original post by Student1256)
in acidic conditions hydroxide ions are never on either side of the equation
So are you suggesting that if I have H+ on the reactant side, no OH- will be made
If I have OH- on the reactant side, no H+ is made?

Thanks
0
4 years ago
#9
(Original post by coconut64)
The reduction of chlorate(V) ions, ClO3 - , to chlorine gas, Cl2. I have to construct a half equation for this.
My answer : 10e- + 2ClO3- + 6H+ --> Cl2 +6OH- I have checked this and the charges do balance..

ANSWER 2ClO3 - + 12H+ + 10e- -> Cl2 + 6H2O

The answer shows water is made but I thought OH- would, am I wrong. But if the charges are balanced then would it be okay? I don't know whether my equation makes sense...

Thanks
ASSUMING ACIDIC CONDITIONS
Start: ClO3- -> Cl2
1) Balance Cl
2ClO3- -> Cl2
2) Balance Oxygen with water
2ClO3- -> Cl2 + 6H20
3) Balance Hydrogen with H+
12H+ + 2ClO3- -> Cl2 + 6H20
4) Balance charge with electrons
10e- + 12H+ + 2ClO3- -> Cl2 + 6H20, as given.
1
#10
(Original post by britishtf2)
ASSUMING ACIDIC CONDITIONS
Start: ClO3- -> Cl2
1) Balance Cl
2ClO3- -> Cl2
2) Balance Oxygen with water
2ClO3- -> Cl2 + 6H20
3) Balance Hydrogen with H+
12H+ + 2ClO3- -> Cl2 + 6H20
4) Balance charge with electrons
10e- + 12H+ + 2ClO3- -> Cl2 + 6H20, as given.
How can you predict H2O is formed, I balanced my equation using OH- ions and the charges do balance too
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4 years ago
#11
(Original post by coconut64)
can't add hydroxide ions as they will neutralise the H+ ions. -> but if you take H2O2 as an example, there are both H+ and OH- in the equation
Look at the example on this page by Jim Clark, you can balance redox half equations involving H202 using H20 and H+ ions.

http://www.chemguide.co.uk/inorganic...equations.html
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4 years ago
#12
(Original post by coconut64)
How can you predict H2O is formed, I balanced my equation using OH- ions and the charges do balance too
By assuming acidic conditions, i.e. presence of H+ [as you see on the LHS], OH- are neutralised by the H+, making water.
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4 years ago
#13
(Original post by coconut64)
So are you suggesting that if I have H+ on the reactant side, no OH- will be made
If I have OH- on the reactant side, no H+ is made?

Thanks
Yes, under alkaline conditions, OH- is involved - balance with H20
Under acidic consitions, H+ is involved - balance with H20

H+ and OH- are never usually used to balance each other in redox equations.
1
#14
Thanks for the help, I get it now
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4 years ago
#15
(Original post by coconut64)
Thanks for the help, I get it now
1
4 years ago
#16
(Original post by coconut64)
Thanks for the help, I get it now
np, just practice and you'l be fine.
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