magnesium hydroxide is 54.87% oxygen by mass. how many grams of oxygen are in 175 g sample of the compound

96 g of O

Explanation:

Mg (OH) ₂ → Magnesium hydroxide

Molar mass → 24.3g/mol. 1 + 16g/mol. 2 + 1g/mol. 2 = 58.3 g/mol

We determine the moles of hydroxide → 175 g. 1mol/58.3g = 3 moles

Let's make some rule of three:

In 100 g of compound we have 54.87 g of O

In 58.3 g of compound we may have (58.3. 54.87) / 100 = 32 g

So, 1 mol of hydroxide has 32 g of oxygen

3 moles of hyroxide may have (3.32) / 1 = 96 g of O