In figure 1, left-hand side (LHS) and the right-hand side (RHS) of the weighing machine are equal to each other. If we add 2 on the RHS, as shown in figure 2, what should we do to equalise LHS and RHS again?
We can balance the following ionic equation by adding
6Fe2+(aq) + Cr2O72-(aq) → 6 Fe3+(aq) +2Cr 3+(aq)