Adding H20 AND H+

[E_Villavicencio 2N]

When balancing some reactions, sometimes water or hydrogen is added to one of the half reactions. Can somebody explain when you add each of those?

[Preston_Dang_1B]

You add H₂O molecules to a half reaction to help balance out the number of oxygens each side of the reaction has. Similarly, you would add H⁺ ions to help balance out the number of hydrogens there are on each side of the equation.

Hope this helps!

[DBaquero]

Also, it should probably be noted that you have to add only H+ and H2O for balancing redox reactions in acidic solutions. If the solution is basic then once you are done adding the H+ and H2O like before, you have to add OH- to both sides to balance out the H+, then you combine the H+ and OH- on the same side of the reaction to make H2O. Finally, you cancel out the H2O on opposite sides.
Hope that wasn't too confusing.

[204863791]

When balancing our redox reaction (by adding H2O, H+, and OH-) can we use the couple H2O/H+ for reactions in an acidic and basic solution both or do we have to use OH- instead of H+ when working with a chemical reaction done in a basic solution?