Answer: Mg3N2 + 6H20 → 2NH3  + 3Mg(OH)2
Explanation:
The reactant side(left side) of the equation is given as magnesium nitride and  water.
magnesium nitride  = combination of magnesium ion and nitrogen ion
Magnesium is the positive end or cation while Nitrogen is the anions or negative end
Mg2+  and  N3-
cross multiply the charges
Mg3N2 = magnesium nitride
H20 = water
Reactant = Mg3N2 + H20
Product  = NH3  + Mg(OH)2
For ammonia
N3- and H+
cross multiply the charges
NH3
For Magnesium hydroxide
Mg2+ and (OH)-
cross multiply the charges
Mg(OH)2
Combining the reactant and the product
Mg3N2 + H20 → NH3  + Mg(OH)2
Balancing the equation, we make the number of atom on the left side equal to the right side.
Mg3N2 + 6H20 → 2NH3  + 3Mg(OH)2
on the reactant side
Mg = 3
N = 2
H = 12
O = 6
On the product side
N Â = 2
H = 6 + 6 = 12
Mg = 3
O = 6
