Question

what is the total of all the coefficients in the balanced equation for the reduction of 1 mol of mno4–?

Answer 1

All the ions must be equal on both sides. Start with the oxygen, for example. We have 4 on the left, so we put 4 in front of the H2O. Now we have 8 hydrogen, so, put 8 in front of the proton. Count the charges and make it balance by placing coefficient in front of the electron.  

Mno4- + 8H+ + 5e- ---> Mn2+ + 4H2O  

1+8+5+1+4=19