Complete and balance the following equation:

NO2{-} + Cr2O7{2-} = Cr{3+} + NO3{-}

http://www.chemteam.info/Redox/Redox.html

To balance this equation, we need to make sure that the same number of each type of atom is present on both sides of the equation.

Let's start by looking at the atoms that are not balanced.

In the reactants, we have one Cr atom, while in the products, we have one Cr atom. That is already balanced.

Next, we have two O atoms in the NO2{-} ion, and seven O atoms in the Cr2O7{2-} ion, giving us a total of nine O atoms on the left side of the equation.

In the products, we have three O atoms in Cr{3+} and three O atoms in NO3{-}, giving us a total of six O atoms on the right side of the equation.

To balance the O atoms, we need to multiply the Cr{3+} ion by 3 and the NO3{-} ion by 2.

The balanced equation is:

2NO2{-} + Cr2O7{2-} = 3Cr{3+} + 2NO3{-}