1. Daily science Jan 14 Write a net ionic equation for the following: ◦Aqueous solutions of calcium chloride and sodium carbonate form the precipitate calcium carbonate ◦HI (aq) + Na 2 S (aq)  H 2 S (g) + NaI (aq) How many donuts are in 6.7 dozen donuts? Use dimensional analysis. If one ream of paper is 500 sheets, how many sheets are in 3.4 reams of paper?

2. The Mole Pg. 71

3. Definition of a Mole A way to group atoms together 12 is to a dozen as 6.02 x 10 23 is to a mole Avogadro’s number = 6.0221367 x 10 23 Based off of number of carbon atoms in 12 g of carbon -12 602000000000000000000000 atoms in one mole Can be used to count: molecules, atoms, particles

4. Converting moles Can write a conversion factor using Avogadro’s number to convert from moles to particles or particles to moles Moles to particles: x 6.02 x 10 23 1 mol Particles to moles: x 1 mol 6.02 x 10 23

5. Examples Determine the number of atoms in 2.50 moles of Zn Calculate the number of molecules of H 2 O in 11.5 moles. How many moles is 5.75 x 10 24 atoms of Al? How many moles is in 3.58 x 10 23 units of ZnCl 2

6. Mass and the Mole Moles of different substances have different masses Called molar mass (mass in grams of one mole of a substance) Units: g/mol

7. Examples What is the molar mass of Silicon? What is the molar mass of Cl 2 ? What is the molar mass of H 2 O

8. Conversions using molar mass To find the mass of a certain amount of a substance, use a conversion factor for molar mass Mass to moles: x 1 mole molar mass Moles to mass: x molar mass 1 mole

9. Examples How many moles are in the following: ◦25.5 g of Ag ◦300.0 g S What is the mass of the following amount of moles: ◦3.45 mol of Co ◦42.6 mol Si

10. Conversions from mass to atoms and atoms to mass Multi step problem Combine both conversion factors Mass to atoms: x1 mol x 6.02 x 10 23 atom molar mass 1 mol Atoms to mass: x 1 mol x molar mass 6.02 x 10 23 1 mol

11. Examples Convert 3.40 x 10 22 atoms of He into grams Convert 1.00 x 10 24 molecules of MgO into grams Convert 55.2 g Li into atoms