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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: theguy on February 20, 2012, 12:28:19 PM

Title: Redox Half Reaction Method
Post by: theguy on February 20, 2012, 12:28:19 PM
I'm having trouble balancing a redox equation.
Specifically the half reaction method.

The equation is NH3 + NO2-  :rarrow: N2 + H2O

No matter how many times I attempt this, I can never seem to get a reasonable answer.

Title: Re: Redox Half Reaction Method
Post by: Borek on February 20, 2012, 12:50:55 PM
If there is no negative charge between products, you won't be able to balance this equation.

Are you sure it is not NH4NO2 decomposition?
Title: Re: Redox Half Reaction Method
Post by: theguy on February 20, 2012, 12:56:19 PM
Okay, I misread the equation. There is no negative charge. It was just a stray mark on my paper. Nonetheless, I've worked it without the negative and still can't get an answer that makes sense.
Title: Re: Redox Half Reaction Method
Post by: Borek on February 20, 2012, 01:22:21 PM
Not every reaction can be balanced. What you wrote is one of these cases without an answer. Compare http://www.chembuddy.com/?left=balancing-stoichiometry&right=balancing-failure

As I suggested earlier, most likely it should be NH4NO2, not NH3NO2.
Title: Re: Redox Half Reaction Method
Post by: theguy on February 20, 2012, 06:41:00 PM
Not every reaction can be balanced. What you wrote is one of these cases without an answer. Compare http://www.chembuddy.com/?left=balancing-stoichiometry&right=balancing-failure

As I suggested earlier, most likely it should be NH4NO2, not NH3NO2.

The reactants aren't supposed to be combined. It's NH3 + NO2.
Title: Re: Redox Half Reaction Method
Post by: Vidya on February 20, 2012, 11:49:08 PM
Ok
check these two balanced half reactions for the reaction given by you
2NH3---> N2 + 6e- + 6H+
8H+ + 6e- + 2NO2-    --------.> N2 + 4H2O
FINAL EQUATIONS IS
2NH3+ 2H+   +  2NO2-    ---> 2N2 +  4H2O
Title: Re: Redox Half Reaction Method
Post by: Hunter2 on February 21, 2012, 01:02:51 AM
No
FINAL EQUATIONS IS

NH3 + H+   +  NO2-    ---> N2 +  4 H2O

But above it was written there was no negative Charge on NO2

So the reduction would be

2 NO2 + 8 H+ + 8 e- => N2 + 4 H2O

8 NH3 => 4 N2 + 24 e- + 24 H+

6 NO2 + 24 H+ + 24 e- =>  3 N2 + 12 H2O

Final would be:

8 NH3 + 6 NO2  => 7 N2 + 12 H2O

Title: Re: Redox Half Reaction Method
Post by: Vidya on February 21, 2012, 01:06:13 AM
No
FINAL EQUATIONS IS

NH3 + H+   +  NO2-   ---> N2 +  4 H2O

But above it was written there was no negative Charge on NO2

So the reduction would be

2 NO2 + 8 H+ + 8 e- => N2 + 4 H2O

8 NH3 => 4 N2 + 24 e- + 24 H+

6 NO2 + 24 H+ + 24 e- =>  3 N2 + 12 H2O

Final would be:

8 NH3 + 6 NO2  => 7 N2 + 12 H2O


I balanced this equation -
 NH3 + NO2- ----> N2 + H2O
in this equation NO2 has  -ve charge
Title: Re: Redox Half Reaction Method
Post by: Hunter2 on February 21, 2012, 02:34:21 AM
In the third post it was written:

Quote
Okay, I misread the equation. There is no negative charge. It was just a stray mark on my paper
Title: Re: Redox Half Reaction Method
Post by: Borek on February 21, 2012, 06:40:13 AM
8 NH3 + 6 NO2  => 7 N2 + 12 H2O

Apparently I did something wrong before, as this is the correct answer.
Title: Re: Redox Half Reaction Method
Post by: neobenzene on March 02, 2012, 01:23:17 AM
I'm not sure if I'm right, but I got

8NH3 + 14NO2 + 32H+ -> 11N2 + 28H2O
Title: Re: Redox Half Reaction Method
Post by: AWK on March 02, 2012, 02:32:21 AM
I'm not sure if I'm right, but I got

8NH3 + 14NO2 + 32H+ -> 11N2 + 28H2O
Charges are unbalances