chemistry-half equations-in alkaline solutions
Half reactions in alkaline solutions

Balancing half equations in an alkaline solution is different to balancing them in an acidic solutions, as we have been doing in the past.
In an acidic solution we balance for oxygen by adding water and balance for hydrogen by adding H+ ions.

However in an alkaline solution we balance for oxygen by adding either water or OH- ions. But the trick is to know which one to use , water or the hydroxide ion.

A simpler approach is to write the half equation as if it were being done under acidic conditions just as you have been shown previously.

Once you have got a balanced half-equation, you then convert it to alkaline conditions by eliminating the H+ ions with the addition of hydroxide ions to both sides of the equation.

Lets see an example below.


Write the overall equation for the reaction when permanganate ions react with bromine ions in basic solution to form MnO2 and BrO3-
Step 1 Write out the reactant and product of the oxidation and reduction reactions
Step 2 Write the half equations as you would for an acidic solution.
Step 3 Balance for electrons and add the two half equations
Step 4 Eliminate the protons by adding hydroxide ions to both sides.
Click on each step.