In order to find the grams needed to prepare this solution, we first need to find the number of moles present in this solution, we will do that by using the Molarity formula:
M = n/V
where:
M = concentration
n = number of moles
V = volume in liters
0.77 = n/0.389
n = 0.299 moles of Mg(OH)2
Now using its molar mass, 58.32 g/mol, we can find the right number of grams needed:
58.32 = 1 mol
x grams = 0.299 moles
x = 17.44 grams of Mg(OH)2
