Question

Mg>Mg(NO3)2>Mg(OH)2>MgO>MgSO4

Answer 1

$Mg + 4HNO3 = Mg(NO_3)_2 + 2 NO_2 + 2 H_2O\\Mg(NO_3)_2 + 2NaOH = 2NaNO_3 + Mg(OH)_2\\Mg(OH)_2 = MgO + H_2O\\MgO + H_2SO_4 = MgSO_4 + H_2O$