Question

Thanks DrBob222 for previous answers.

Question: Balance the following reactions by the oxidation number method.

a) I2 + HNO3 --> HIO3 + NO2 + H2O

b) MnO4- + H+ + Cl- --> Mn2+ + Cl2 + H2O

Answer 1

You need to tell me what you don't understand about these. I don't want to simply give you the answers. But I can help you get started.
a. I goes from zero on the left to +5 on the right; N goes from +5 on the left to +4 on the right. (A tip to help: Many students make the mistake on I2 of saying "I goes from zero on the left to +5 on the right" and they then make that a loss of 5 electrons BUT there are two I atoms involved. Therefore, FIRST, make that 2HIO3 on the right (so we are talking about the same number of I atoms) THEN I goes from a total of zero on the left to a total of +10 on the right and that makes a loss of 10 electrons for the 2I atoms.)

b. Mn is +7 on the left and +2 on the right. Cl is -1 on the left and zero on the right (note again the disparity in the Cl). So you make that 2 Cl on the left FIRST THING. Then the -2 total on the left goes to zero on the right for two Cl atoms.