Fill in the coefficients that will balance the following reaction: a0zn + a1fe(no3)2 → a2znno3 + a3fe

2Zn + Fe(NO3)2 -> 2Zn(NO3)2 + Fe.

In other words: coefficients for a0 and a2 are 2, a1 and a3 are blank/0.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-