Balance the follow equation using change in oxidation number method. (1) P4 + HNO3 = H3PO4 +NO2 + H2O (2) Na2Cr2O7 + FeCl2 + HCl = CrCl3 + NaCl + FeCl3 + H2O

Answer 1

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#1. P changes from zero on the left to +5 on the right (for EACH--emphasize EACH--atom). N changes from +5 on the left to +4 on the right.
#2. Cr changes from +6 on the left to +3 on the right for EACH atom; Fe changes from +2 on the left to +3 on the right.
http://www.chemteam.info/Redox/Redox.html