1. The Mole Intro to Stoichiometry

2. Measurements in Chemistry Atomic Mass: the mass of an atom of a certain element in atomic mass units (amu). 1 amu = 1.66 x 10 -24 g Formula Mass: the sum of atomic masses of all atoms in a compound units are still amu

3. Atomic mass and formula mass are impractical for laboratory work. Why?

4. 1. We measure masses by grams, not amu 2. If the atomic mass or formula mass is converted to grams, the number is still so tiny that it would be impossible to measure.

5. The Mole A Mole is 6.02 x 10 23 of something 1 mole of an element contains 6.02 x 10 23 atoms of that element 1 mole of water contains 6.02 x 10 23 molecules of water This number is known as Avogadro’s number

6. 1 mole of an element (or compound) equals that elements atomic mass (or formula mass) in grams This is called the Molar mass Formula mass of water = Molar mass of water =

7. What is the molar mass of Nickel (III) carbonate?

8. Mole Conversions Mass and Moles 1 mol = molar mass (g)

9. Particles and Moles Particles = molecules, atoms, formula units, ions, etc. 1 mole = 6.02x10 23 particles

10. Moles and Volume of a Gas This conversion only works at STP 0 degrees Celsius and 1 atm of pressure 22.4 L / 1 mole

11. Multistep conversions What would be the mass in grams of 8.0 x 10 24 molecules of sodium hydroxide? What volume would 15 g of oxygen gas occupy at STP?

12. Percentage Composition The mass of each element in a compound compared to the entire mass of the compound and then multiplied by 100 Can be calculated 2 ways: 1. From the chemical formula 2. From experimental analysis of a sample

13. 1. From the chemical formula: CaCl 2

14. 2. From experimental analysis of a sample: Analysis of a 4 g sample of an unknown compound reveals that it contains 2.3 g sodium, 1.6 g oxygen, and 0.1 g hydrogen. Find the percent composition.

15. A sample of a compound has a mass of 5 grams and is determined to be 13% carbon, 2.2% hydrogen, and 84.8% fluorine. What mass of each element is in this sample?

16. Empirical Formula The empirical formula gives the simplest whole-number ratio of the atoms in a compound.

17. 1. Finding empirical formula from percent composition. -What is the empirical formula of a compound that is 80% carbon and 20% hydrogen?

18. 2. Determine the empirical formula for a compound containing 7.30 g Na, 5.08 g S, and 7.62 g O.

19. Molecular Formula Molecular formulas show the actual number of atoms of each element in a compound.  Always a whole number multiple of the empirical formula  Determined by comparing the molar mass of the unknown compound with the molar mass of the empirical formula.

20. Ribose is a sugar found in DNA and RNA. It has a molar mass of 150 g/mol and a chemical composition of 40% carbon, 6.67% hydrogen, and 53.3% oxygen. Determine the molecular formula.