Question

Balance the equation, if necessary, for the reaction between magnesium sulfate and
ammonia.
MgSO4 + NH4OH → (NH4)2SO4 + Mg(OH)2

Answer 1

It's really simple - you just have to count atoms. There's one Mg in both sides, so no coefficient is necessary in front of it. There are, however, two OH groups in Mg(OH)2 but only one in NH4OH, therefore you balance the equation like this:
\[MgSO _{4}+2NH _{4}OH \rightarrow Mg(OH)_{2}+ (NH _{4})_{2}SO _{4}\]