Question

Balance the reaction Sn + HNO3--> sno2 + no2 + H2O

Answer 1

In this problem we have a redox reaction which could be balanced through the half reaction method. First we must write the oxidation numbers for all the elements involved in the reaction as follows:

As we can see in the former equation only two elements change its oxidation number: Sn and N. Now we write the half reactions both oxidation and reduction:

The next step is to balance the number of electrons in the half reactions showed above. Note that Sn losts 4 electrons and N wins 1 electron, so we have multiply the reduction reaction by 4 in order to balance the quantity of electrons:

=

Adding the two half reactions we get:

Now we must transfer the coefficients from the precedent equation to the first one as showed bellow:

The last step is to balance the remaining elements (H and O) by trial and error. In this case we observe in the left hand of the equation that there are 4 atoms of H and 12 atoms of O, so if we put the number 2 as coefficient for water we can confirm that the equation is balanced.

Then the balanced equation is: