I don't do it that way. That way is the quickest and easiest, so I'm told, and the way I do it long and the hardest way BUT I do it. Perhaps this will help you.
1. Divide into the two half equations.
2. Preliminarily balance the atoms that are changing; i.e., for Cr2O7^2- to Cr^3+ you will want it to read Cr2O7^2- --> 2Cr^3+ so you are balancing apples with apples and not apples with oranges.
3. Cr^3+ ==> CrO4^2-
Determine oxidations states. Cr^3+ is 3+ and Cr in CrO4^2- is 6+.
4. Add electrons to the appropriate side to balance the change in oxidn state.
Cr^3+ ==> CrO4^2- + 3e
5. Determine charge on both sides and
a. If acid solution add H^+ to balance charge
b. If basic solution add OH^- to balance charge.
Charge is +3 on left; -5 on right. Add 8 OH^- to left to read
8OH^- + Cr^3+ ==> CrO4^2- + 3e
6. Now add H2O to the appropriate side to balance. That will read
8OH^- + Cr^3+ ==> CrO4^2- + 3e + 4H2O
7. Check it for three things.
a. atoms balance. yes. 8O, 8H, 1Cr each side.
b. charge balance. yes -5 each side
c. Oxdn state change balances. yes. Cr goes from 3+ to 6+ and that's a loss of 3e for Cr left to right.
Happy balancing.
Complete and balance the equation for this reaction in basic solution? Redox reaction Cr is oxidized to CrO42– and Fe3 is reduced to Fe2...?
For a particular redox reaction Cr is oxidized to CrO42– and Fe3 is reduced to Fe2 . Complete and balance the equation for this reaction in basic solution. Phases are optional.
Cr+Fe{3+}--->CrO4{2-}+Fe{2+}
I understand how to solve a problem like this in an acidic solution. Add H+ and H2O to balance Oxygen and Hydrogen and finally add electrons and then add the equations together. I just don't understand how to do it in a basic solution. Adding the OH always confuses me because I'm adding oxygen and hydrogen at the same time and then when I go to add H2O I just get confused. Any help is really appreciated!
2 answers
So in this method you don't use electrons to balance the charge you use either H+ or OH-?
2 answers