When I was in class 8th or 7th , I used to complete and balance equations by logic. For example : 2Na+2H2O ---> 2NaOH+H2 NaNO3+H2SO4 ---------> HNO3 + NaHSO4 But now , presently when I am 14 years , (about to complete 14 though) and in class 10th , I always come across the equations which can have various possible reactions. For example : Pb+HNO3 ---> ? In class 8th , logically I solved it : Pb+2HNO3 ---> Pb(NO3)2 + H2 People used to say : Very good ! You got it correct ! Now that I am in class 10th I came across same equation : Pb+HNO3 ---> ? I solved it : Pb+2HNO3 ----> Pb(NO3)2 + H2 Now people say : Don't you know such simple reaction !! Products will be : Pb+6HNO3 ----> Pb(NO3)2 + 3H2O + 3NO2 What is this !!! I will have to cram the equations or what ?! Other equations : Me: 2P+6HNO3 ---> 2P(NO3)3 + 3H2 People : You don't know such a simple reaction ! P + 5HNO3 -----> H3PO4 + H2O + 5NO2 Me : NH4NO3 ---> NH3 + HNO3 People : It is wrong ! Are you mad ! If this is correct then why would people prefer Ostwald's process of preparing HNO3 instead of this ! Please help ! Please complete this equation also : K4Fe(CN)6 + H2SO4 + H2O -----> ? Assistance will be much appreciated. Thanks in advance.