balancing redox rxns?

[unsung]

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will we have to know how for the MCAT?

For ex, Al --> Al(OH)4- and NO2- --> NH3 in basic conditions. How would that be balanced?

 

[bluemonkey]

will we have to know how for the MCAT?

For ex, Al --> Al(OH)4- and NO2- --> NH3 in basic conditions. How would that be balanced?

split your reaction into its half reactions.
proceed accordingly for each half-reaction:
balance mass:
1st balance your actual redox participant
2nd balance your oxygens by adding H20
3rd balance H's:
Use H+ in acidic solutions
In basic solutions use H+ as though it were acidic and then add OH- to both sides until the H+ are neutralized to H20. Cancel out any H20's that show up on both sides.
Balance Charge:
Add electrons to each side of the half reaction to get equal charge.
Then multiply each half reaction to get the least common multiple for the number of electrons.
Add to two half-reactions canceling out anything that shows up on both sides.

There are many different ways to balance redox, but this has worked well for me!

 

[sunsfan]

Surprised to see this in my review books, too.
I wish this wasn't on the MCAT.
I remember this to be such a tedious exercise. 😴