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Topic: Cannot understand this redox reaction  (Read 471 times)

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Offline Marcool

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Cannot understand this redox reaction
« on: January 10, 2021, 11:32:24 AM »
Hi
I'm having an issue trying to understand how to balance this redox reaction because I'm not entirely sure if the reaction makes sense in the first place.

The first thing I did was to balance the atoms on the left and on the right, but when i try to understand the oxidizing and reducing agent I get a bit confused.

Could you help me?


Offline mjc123

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Re: Cannot understand this redox reaction
« Reply #1 on: January 11, 2021, 05:33:18 AM »
What are your thoughts? Can you assign oxidation numbers to the atoms?

Offline Marcool

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Re: Cannot understand this redox reaction
« Reply #2 on: January 11, 2021, 07:15:34 AM »
Chlorine goes from +5 to +4 so it is reduced, and there's oxygen oxidizing from -2 to 0.

Is this correct?

Offline mjc123

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Re: Cannot understand this redox reaction
« Reply #3 on: January 11, 2021, 08:19:31 AM »
Yes

Offline AWK

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Re: Cannot understand this redox reaction
« Reply #4 on: January 11, 2021, 08:23:47 AM »
Yes, that is correct. But this redox equation causes trouble.
It is easy to solve them by the algebraic method or by the method of oxidation degrees, but by making the electron balance from the right side of the equation to the left side (KClO3 + ... <== O2 + ClO2 + ...)
AWK

Offline Marcool

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Re: Cannot understand this redox reaction
« Reply #5 on: January 11, 2021, 09:20:08 AM »
Yes, that is correct. But this redox equation causes trouble.
It is easy to solve them by the algebraic method or by the method of oxidation degrees, but by making the electron balance from the right side of the equation to the left side (KClO3 + ... <== O2 + ClO2 + ...)

Would you be so kind to illustrate me better how to solve this? I'm getting confused..

Offline AWK

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Re: Cannot understand this redox reaction
« Reply #6 on: January 11, 2021, 09:30:46 AM »
Just solve this equation
 K2SO4 + O2 + ClO2 + H2O = KClO3 + H2SO4
AWK

Offline Marcool

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Re: Cannot understand this redox reaction
« Reply #7 on: January 11, 2021, 10:34:27 AM »
Just solve this equation
 K2SO4 + O2 + ClO2 + H2O = KClO3 + H2SO4
Maybe I still have to study more cause I can't work out how to balance this equations. I get them all wrong. Thanks anyway

Offline AWK

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Re: Cannot understand this redox reaction
« Reply #8 on: January 11, 2021, 10:39:59 AM »
O2 :larrow: 2ยท2e
Cl :rarrow: 1e
AWK

Offline Marcool

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Re: Cannot understand this redox reaction
« Reply #9 on: January 11, 2021, 11:56:41 AM »
I don't understand what you're trying to say... sorry but I'm really confused because I don't have something to write for the oxygen equation...

ClO3- + 2H+ + e- --> ClO2 + H2O

ClO3- + H2O --> 1/2 O2 + ClO3 + 2H+ +2e-

I then multiply times 2 the first equation but then I get confused...

The solution is meant to be

2KClO3 + H2SO4 --> K2SO4 + 1/2 O2 + 2ClO2 + H2O

So I could work this out even without doing any redox, just by balancing the masses...

Offline AWK

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Re: Cannot understand this redox reaction
« Reply #10 on: January 11, 2021, 12:09:10 PM »
O2 + 4H+ + 4e- = 2H2O
ClO2 + H2O = ClO3- + 2H+ + e-
AWK

Offline Marcool

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Re: Cannot understand this redox reaction
« Reply #11 on: January 11, 2021, 12:28:21 PM »
Thanks a lot!
Now I think I got it.

I basically, in the end, after canceling out the same stuff on both sides of the reaction, was left with:

2 ClO3- + 2H+ --> 2ClO2 + 1/2 O2 +H2O

I returned to the molecular formulas and also understood that those two hydrogen atoms on the left were coming from the sulphuric acid. So I just converted 2H+ into H2SO4 and, clearly, added again K2SO4 on the right.

2 KClO3 + H2SO4 --> K2SO4 + 1/2 O2 + 2 ClO2 + H2O

Alternatively, if one doesn't like the half integers, they could just multiply everything times two.

Is this correct?

Offline AWK

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Re: Cannot understand this redox reaction
« Reply #12 on: January 11, 2021, 01:18:31 PM »
4 KClO3 + 2 H2SO4 = 2 K2SO4 + O2 + 4 ClO2 + 2 H2O
AWK

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