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### Topic: Balance of redox reaction  (Read 303 times)

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#### Glitch000

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• Mole Snacks: +0/-0 ##### Balance of redox reaction
« on: November 17, 2021, 09:16:43 AM »
hi, i can't resolve this redox reaction, can someone help to find the error?

P4O6 + I2 = P2I4 + P4O10

first i found the oxidation number and then i wrote the semi reaction and I balanced them:

Red1:   12H+ + 4e- + P4O6 = 4P+2 + 6H2O
Red2:   4e- + 2I2 = 4I-

12H+ + 8e- + P4O6 + 2I2 = 4P+2 + 6H2O + 4I-

Ox: 4H2O + P4O6 = P4O10 + 8e- + 8H+

The total arrives:
12H+ + 8e- + P4O6 + 2I2 + 4H2O + P4O6 = 4P+2 + 6H2O + 4I- + P4O10 + 8e- +8H+

at the end my balanced reaction arrives:
2P4O6 + 2I2 + 4H+ = 4P2I4 + P4O10 + 2H2O

The reaction is wrong because the exact balanced reaction is this:
5P4O6 + 8I2 = 4P2I4 + 3P4O10

I don't understand were is my error... #### Borek ##### Re: Balance of redox reaction
« Reply #1 on: November 17, 2021, 11:07:32 AM »
Wow. Just wow. I would never think it is possible to overcomplicate thing by that much. Try to balance just by inspection (most likely starting with iodine will be the easiest approach).

But:

Red1:   12H+ + 4e- + P4O6 = 4P+2 + 6H2O
Red2:   4e- + 2I2 = 4I-

12H+ + 8e- + P4O6 + 2I2 = 4P+2 + 6H2O + 4I-

This is already wrong - when you add these two reactions you assume they occur in some particular ratio. Why?
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#### Orcio_Dojek ##### Re: Balance of redox reaction
« Reply #2 on: November 17, 2021, 11:13:35 AM »
Quote
at the end my balanced reaction arrives:
2 P4O6 + 2 I2 + 4 H+ = 4 P2I4 + P4O10 + 2 H2O
Of course its wrong. Did you ever read what have you written here ?

Where is the error:
Quote
Red1:   12 H+ + 4 e- + P4O6 = 4 P2+ + 6 H2O
Red2:   4 e- + 2 I2 = 4 I-