Question

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Calculate the number of moles in 17.8 g of the antacid magnesium hydroxide, Mg(OH)2

Answer 1

n = m/M
n - number of moles
m - mass
M - molar mass

Answer 2

Molecular weigh of Mg(OH)2 =12+(8*2)+(1*2)=30
mass= 17.8g
if mass=moles * molecular weight
then moles =mass/molecular weight
moles of Mg(OH)2=17.8/30 = 0.583 to 3d.p

Answer 3

molar mass of Mg(OH)2 = 24 + (17)*2 = 58.
no of moles = m/M
m - given mass
M- Molar mass