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See explanation

Explanation:

Let us recall that the basic rule in writing balanced chemical reaction equations is that the number of atoms of each element on the right hand side of the reaction equation is the same of the number of atoms of the same element on the left hand side of the reaction equation.

The reaction of red hot iron and steam is written as follows;

3Fe + 4H2O → Fe3O4 + 4H2.

The decomposition reaction of ammonium dichromate is written as;

(NH4)2Cr2O7 → N2 + Cr2O3 + 4H2O

Reaction of aluminium, sodium hydroxide and water is as follows,

2Al + 2NaOH + 2H2O > 2NaAlO2 + 3H2

Reaction of potassium bicarbonate with sulphuric acid;

2KHCO3 + H2SO4 > K2SO4 + 2H2O + 2CO2

Reaction of zinc and sodium hydroxide is as follows;

Zn + 2NaOH→Na2ZnO2 + H2

the awnser is group 12