1. Counting by weighing Calculate the amount of pennies in the cup by weighing them. You may take 10 pennies out of the cup to weigh them, but do not count what is in the cup Atoms are too small to count so we weigh an amount (mole) and calculate the number

2. Some words mean numbers Pair Dozen Baker’s dozen Gross Ream

3. Mole 1 mole = 6.02 x 10 23 representative particles ( the number of carbon-12 atoms in 12.00 g obtained by counting by weighing)

4. Atom, Molecule and Ions Representative particles – smallest particle of that substance Substance Representative Particle element atom molecular compound molecule (covalent bond) ionic compoundformula unit

5. Practice: 1.Determine the number of FU in.866 moles of AgNO 3 ? 2.Find the molecules in 0.98 moles of Cl 2 3.Determine the moles in 7.83 x 10 17 atoms of Fe

6. Molar Mass (counting by weighing mass) Mass of 1 mole of a substance Element atomic mass in g Compound add up all the atomic masses for all the atoms in the substance

7. Calculate the Molar mass Ca H 2 KNO 3 (NH 4 ) 2 S

8. Remember 1 mole = 6.02 x 10 23 r.p. 1 mole= molar mass(g)

9. Try these: Calculate the moles of 1.2 g H 2 Calculate the moles of 5.6 x 10 25 f.u. Fe(OH) 3 Calculate the grams of 6.7 moles SO 3 Calculate the molecules of 4.0 moles of CO

10. Molar Volume The volume of 1mole of a gas at standartd temperature – 0 o C standard pressure – 1 atmosphere (pressure at sea level) 1 mole gas at STP = 22.4 L

11. Remember 1 mole = 6.02 x 10 23 r.p. 1 mole= molar mass(g) 1 mole=22.4 L gas

12. Multistep problems How many atoms on 47.8L of Ar? How many fu in 18.9 g NaCl? How many g in 4.5 x 10 13 atoms K?

13. Percent Composition % element = g element x 100% g total

14. Formulas Empirical simplest whole number ratio Molecular Formula actaul number of atoms in the formula

15. Empirical formula Get moles Use moles as subscripts Divide by common factor (usually smallest number) Get whole number

16. Practice: A compound has 13.5 g Ca 10.8 g O.675 g H What is its empirical formula?

17. Molecular formula Set up table: Molar Massformula Empirical Molecular

18. Reactions of an Iron Nail Do steps 1,2,3,4,5 Return to class Do steps6,7,8,9,10,11

19. Chemical Measurements Atomic Mass The weighted average of all the mass numbers for all the isotopes of the atom (a.m.u.) Formula Mass The sum of all the atomic masses for all atoms in the compound. (a.m.u.)

20. Calculate the atomic mass or formula masses Na Cl Br 2 NaCl H 2 O Mg(OH) 2 22.99 amu 35.45 amu 159.80 amu 58.45 amu 18.02 amu 58.33 amu

21. Molar mass element The mass of 1 mole = atomic mass (g) What is the mass of 1 mole of He? Pb? Cl?

22. Molar Mass =The mass of 1 mole ( 6.02 x 10 23 ) of representative particles =The atomic mass in g =The formula mass in g