2. You need a calculator AND periodic table for today’s notes

3. Percent Composition
Divide mass of each element by total compound mass and multiply by 100
Can be found experimentally or from the formula itself

4. Sample Problem
A g sample of an unknown compound is extracted from the roots of a plant. Decomposition of the sample produces g of carbon, g of oxygen, and g of hydrogen. What is the percent composition of the compound?

5. Sample Problem
A g sample of an unknown compound is extracted from the roots of a plant. Decomposition of the sample produces g of carbon, g of oxygen, and g of hydrogen. What is the percent composition of the compound?
C = %
O = %
H = 6.67 %

6. C6H12O6 is glucose molecular formula CH2O is glucose empirical formula
Empirical formula- is the simplest whole number ratio of a compound.
Molecular formula-shows the actual number of atoms in the molecule.
The molecular formula is some multiple of the empirical formula.
C6H12O6 is glucose molecular formula
CH2O is glucose empirical formula

7. Empirical Formulas Turn mass into moles
Divide by smallest moles (from step 1)
Write formula (numbers are subscripts)

8. Sample Problem
Determine the empirical formula for a compound containing g Cl
and g Ca.

9. Sample Problem
Determine the empirical formula for a compound containing g Cl
and g Ca.
CaCl2

10. Sample Problem
A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and g H. What is the empirical formula for the compound?

11. Sample Problem
A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and g H. What is the empirical formula for the compound?
Ca(OH)2

12. You must be given molecular mass in the problem.
Molecular Formula
Find the empirical formula
Find Molar mass of empirical formula
Divide molecular mass by Molar mass
Multiply empirical formula by answer.
You must be given molecular mass in the problem.

13. Sample Problem
Ribose is an important sugar that is found in DNA and RNA. Ribose has a molar mass of 150g and an empirical formula of CH2O. Based on this information, determine the molecular formula for ribose.

14. Sample Problem
Ribose is an important sugar that is found in DNA and RNA. Ribose has a molar mass of 150g and an empirical formula of CH2O. Based on this information, determine the molecular formula for ribose.
C5H10O5

15. Sample Problem
Find the molecular formula for a compound that contains 4.90 g N and 11.2g O. The molecular mass of the compound is 92.0 g/mol.

16. Sample Problem
Find the molecular formula for a compound that contains 4.90 g N and 11.2g O. The molecular mass of the compound is 92.0 g/mol.
N2O4