If excess [tex]H_2O[/tex] is used as stated in the illustration the amount of [tex]Mg_3N_2[/tex] that would be required would be 7.57 grams
From the equation of the reaction:
[tex]Mg_3N_2(s) + 6H_2O(l) --- > 3Mg(OH)_2(s) + 2NH_3(g)[/tex]
Since the yield is 80% of the theoretical value, in order to make 10g, the theoretical yield would be 12.5 g.
Mole ratio of [tex]Mg_3N_2[/tex] and [tex]Mg(OH)_2[/tex] = 3:1
Mole of 12.5 g [tex]Mg(OH)_2[/tex] = 12.5/53.32 = 0.225moles
Equivalent mole of [tex]Mg_3N_2[/tex] = 0.124/3 = 0.075 moles
Mass of 0.0041 moles [tex]Mg_3N_2[/tex] = 0.075 x 100.95 = 7.57 grams
More on stoichiometric calculations can be found here: https://brainly.com/question/8062886