Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Xovan on May 29, 2006, 09:47:50 PM
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Hi I'm having a bit of trouble figureing out a certain problem. Its in a basic solution.
AsO43- + NO2- --> AsO2- + NO3-
The thing is to balance out the equation using the half reaction method. I know its probably As losing 2e- but what is gaining electrons? If nothing then why is there 2 spectator ions?
How would adding H2O and H+ change things?
I figure the change in configuration of NO2- and NO3- has something to do with it but I don't see what exactly.
edited for objectional title, and new thoughts
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Actually, the arsenic atom gained 2 electrons. Its oxidation state went from 5+ to 3+. The nitrogen, on the other hand, lost 2 electrons, going from 3+ to 5+.
As for H+ & H2O, look at the number of oxygens & total charge on each side of your equation. It's not quite balanced, though you can balance this if you include the H+ & H2O.
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Thanks for the correction.
Therefor...
AsO4 + 4H+ + 2e- --> AsO2 + 2H2O is reduced and As is the Oxidizing Agent
NO2 + H2O --> NO3 + 2H+ + 2e- is oxidized and N is the Reducing Agent
AsO4+ 4H+ + 2e- + NO2 + H2O --> AsO2 + 2H2O + NO3 + 2H+ + 2e-
right?
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:) You got it.
Though you just need to cancel out some things and leave the charges on. So you can write...
AsO43- + 4H+ + 2e- + NO2- + H2O --> AsO2- + 2H2O + NO3- + 2H+ + 2e-
...as this:
AsO43- + 2H+ + NO2- --> AsO2- + H2O + NO3-
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Thanks for the help.
Though I didn't write the charges because I was tired of writing sup /sup and sub /sub.
:D
Thanks again for the help.
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http://www.chembuddy.com/?left=balancing-stoichiometry&right=half-reactions-method