1. Aim: How to determine Empirical and Molecular Formula DO NOW: Copy the question. Here is data from an experiment: 1.Mass of empty crucible + cover = 11.70 g 2.Mass of crucible + cover + hydrated crystal (before heating) = 14.90 g 3.Mass of crucible + cover + anhydrous salt (after heating) = 14.53 g What is the % by mass of the water in the hydrated crystal?

2. Objectives: determine the empirical formula from a molecular formula determine the molecular formula, given the empirical formula and the molecular mass How to determine empirical and molecular formula

3. Empirical Formula vs. Molecular Formula Empirical Formula tells us what elements are present in the compound in the simplest whole number ratio of elements. Molecular formula tells which elements are present in the compound and the actual number of each element. How to determine empirical and molecular formula

5. Determining empirical formula from molecular formula Divide all the subscripts by their greatest common factor. How to determine empirical and molecular formula

6. Determining Empirical Formula from Molecular Formula 1. Which of the following substances has an empirical formula that is different from that of the others? a.C 4 H 8 O 4 b.C 3 H 6 O 2 c.C 2 H 4 O 2 d.C 6 H 12 O 6 How to determine empirical and molecular formula

7. Determining Empirical Formula from Molecular Formula How to determine empirical and molecular formula Write an empirical formula for the product. (first find molecular formula)

8. Determining Molecular Formula from Empirical Formula The molecular formula of a compound is a multiple of its empirical formula. The molecular formula may be determined by dividing the molar mass of the compound by the empirical molar mass. When you divide you find which multiple it is of the empirical formula. How to determine empirical and molecular formula

9. Determining Molecular Formula

10. Step 1: Determine molar mass of empirical formula CH 3 = C + 3H = (12.0 g/mol) + (3 x 1.0 g/mol) = 15.0 g/mol How to determine empirical and molecular formula

11. Step 2: Divide molecular molar mass of compound (75. 0 g/mol) by empirical molar mass. How to determine empirical and molecular formula

12. Practice What is the molecular formula of a compound that has an empirical formula of NO 2 and molecular mass of 92.0 g? How to determine empirical and molecular formula

13. Practice Determine the molecular formula for a compound that has the empirical formula CH 2 O and a molar mass of 120. grams per mole. How to determine empirical and molecular formula