2. Calculate the percent by mass composition of C2H4O2..
Calculate the molar mass of the compound
Express the mass of each element within the compound as a percentage of the molar mass of the compound. Make sure to account for multiple atoms.
Multiply by 100% to convert to a percentage.

3. Calculate the percent by mass composition of C2H4O2.

4. Mass of pure chemical
Total mass of sample
% purity = x 100

5. Consider the reaction of magnesium hydroxide with phosphoric acid.
3Mg(OH)2 + 2H3PO4  Mg3(PO4)2 + 6H2O
Calculate the mass of Mg3(PO4)2 that will be formed (assuming a 100% yield) from the reaction of 15.0 g of 92.5% Mg(OH)2 with an excess of H3PO4.
Mass of sample
This would be percentage purity

6. Consider the reaction of magnesium hydroxide with phosphoric acid.
3Mg(OH)2 + 2H3PO4  Mg3(PO4)2 + 6H2O
Calculate the mass of Mg3(PO4)2 that will be formed (assuming a 100% yield) from the reaction of 15.0 g of 92.5% Mg(OH)2 with an excess of H3PO4.
x 100
Mass of pure chemical = % purity X Total mass of sample
mass Mg(OH)2 = 15.0 x = g
Mass of pure chemical
Total mass of sample
% purity =
100

7. Consider the reaction of magnesium hydroxide with phosphoric acid.
3Mg(OH)2 + 2H3PO4  Mg3(PO4)2 + 6H2O
(b) Calculate the mass of 88.5% Mg(OH)2 needed to make 127 g of Mg3(PO4)2, assuming a 100% yield.
This would be percentage purity
You would need to you this to calculate the mass of pure chemical required

8. Consider the reaction of magnesium hydroxide with phosphoric acid.
3Mg(OH)2 + 2H3PO4  Mg3(PO4)2 + 6H2O
(b) Calculate the mass of 88.5% Mg(OH)2 needed to make 127 g of Mg3(PO4)2, assuming a 100% yield.
127g Mg3(PO4)2
1 mole Mg3(PO4)2
3 mole Mg(OH)2
58.3g Mg3(OH)2
84.5g Mg3(OH)2
262.9g Mg3(PO4)2
1 mole Mg3(PO4)
1 mole Mg(OH)2

9. Consider the reaction of magnesium hydroxide with phosphoric acid.
3Mg(OH)2 + 2H3PO4  Mg3(PO4)2 + 6H2O
(b) Calculate the mass of 88.5% Mg(OH)2 needed to make 127 g of Mg3(PO4)2, assuming a 100% yield.
84.5g
Mass of pure chemical
Total mass of sample
% purity = x 100
88.5
Total mass of sample =
84.5g
X 100
88.5
Total mass of sample = grams