mass calculations

Question 1

what is the formula for the percentage mass of an element in a compound

Answer 1

relative mass of the element / mass of whole compound

Question 2

steps of the empirical formula

Answer 2

1. list all the elements and their masses
2. divide each mass given, by the relative mass
3. multiply both by 10 to get whole numbers
4. simply down into a small ratio

Question 3

find the mass of magnesium oxide that is produced when 60g of magnesium is burned in the air

Answer 3

1. write out the balanced equation
2. work out the relative mass of the substance you want
3. divide to find 1g
4. times by the gram you want