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

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

Sample Problem A 0.2370 g sample of an unknown compound is extracted from the roots of a plant. Decomposition of the sample produces 0.09480 g of carbon, 0.1264 g of oxygen, and 0.0158 g of hydrogen. What is the percent composition of the compound?

Sample Problem A 0.2370 g sample of an unknown compound is extracted from the roots of a plant. Decomposition of the sample produces 0.09480 g of carbon, 0.1264 g of oxygen, and 0.0158 g of hydrogen. What is the percent composition of the compound? C = 40.00 % O = 53.33 % H = 6.67 %

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

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

Sample Problem Determine the empirical formula for a compound containing 2.128 g Cl and 1.203 g Ca.

Sample Problem Determine the empirical formula for a compound containing 2.128 g Cl and 1.203 g Ca. CaCl2

Sample Problem A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and 0.675 g H. What is the empirical formula for the compound?

Sample Problem A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and 0.675 g H. What is the empirical formula for the compound? Ca(OH)2

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.

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.

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

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.

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