Chemical equations are becoming my greatest nightmare

[sankalpmittal]

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.

 

[DrDu]

Chemistry would be a rather limited science if there were only one possibility for each mixture to react. Mostly there are numerous different possibilities. In the case of the reactions involving HNO3, you have to consider that nitrate is a much more strongly oxidizing agent than are hydronium ions.

 

[sankalpmittal]

Chemistry would be a rather limited science if there were only one possibility for each mixture to react. Mostly there are numerous different possibilities. In the case of the reactions involving HNO3, you have to consider that nitrate is a much more strongly oxidizing agent than are hydronium ions.

But it is wrong for people to start accusing me , right ? As you can see that my equations above (post #1) are correct.

Can you illustrate any logic behind it or any trick to complete such equations ?