1. THE MOLE “n”  The mole term is similar to the “dozen” term.  Just as a dozen represents “12”; the mole represents 6.022 x 10 23. A very large amount.  This is due to atoms & molecules being very small. ÖThe mole is also referred to as Avogadro’s number, N A Ö1 mole = N A = n = 6.022 x 10 23 particles ÖParticles could be atoms, molecules, ions, electrons, even eggs.

2. THE MOLE & ATOMIC MASS  The atomic mass (weight) is measured in reference to the mole. MOLAR MASS  The atomic mass is also known as the MOLAR MASS.  The atomic mass = mass of an element DIVIDED by 1 mole of that element.  Atomic mass = mass/mole or m/n.  Units for atomic mass is grams per mole or g/mol. For example: H = 1.008 amu = 1.008 g/mol = 6.022 x 10 23 atoms = 1 molar mass

3. CALCULATIONS INVOLING THE MOLE. Fill in the blank. ¬A mole of oxygen atoms contain _______ atoms and weighs ______ grams. ­A mole of oxygen contains _____ molecules and ____ atoms and weighs _______ grams. A mole of fluorine atoms contain _________ atoms and weighs _____grams. ­A mole of fluorine contains __________ molecules and ________ atoms and weighs ______ grams. 6.022 x 10 23 15.999 6.022 x 10 23 2(6.022 x 10 23 ) 31.998 or 2(15.999) 6.022 x 10 23 19.00 6.022 x 10 23 12.044 x 10 23 38.00

4. CALCULATIONS INVOLING THE MOLE. Dimensional Analysis Approach. ¬How many moles of Mg are contained in 15.0 grams of Mg? Answer: 15.0 g (1 mole/24.3g) = 0.617 moles. Remember if “g” is on top originally then inside the parenthesis it must go on the bottom. ­How many atoms of Mg are contained in 15.0 grams of Mg? Answer: 15.0 g (1 mole/24.3g) = 0.617 moles. then 0.617 mol (6.022 x 10 23 atoms/ 1 mole) = 3.72 x 10 23 atoms.

5. MOLAR MASS FOR COMPOUNDS The molar mass of any substance is the mass in grams for one mole of that substance. H 2 SO 4 contains 2-H atoms, 1-S atoms & 4-O atoms. Each of those atoms contribute mass to the whole compound. 2H + 1S + 4O = H 2 SO 4 so 2(1.008 g/mol) + 1(32.06 g/mol) + 4(15.99 g/mol) = 98.04 g/mol ¬Calculate the molar mass of the following compounds. 1. K 3 PO 4 2. Ca(OH) 2 3. (NH 4 ) 2 SO 3 4. SrCl 2. 6H 2 O answer on next page.

6. MOLAR MASS FOR COMPOUNDS Answer to molar mass question. 1. 3K + P + 4O = 212 g/mol 2. Ca + 2O + 2H = 74 g/mol 3. 2N + 8H + S + 3O = 116 g/mol 4. Sr + 2Cl + 12H + 6O = 267 g/mol Word Problems: ¬How many grams does one molar mass of BaCO 3 weigh? Answer: : 197 g/mol

7. CALCULATIONS INVOLING THE MOLE for COMPOUNDS. Dimensional Analysis Approach. ¬How many grams of NH 4 NO 3 are contained in 3.15 moles of NH 4 NO 3 ? Answer: 2N + 4H + 3O = 80 g/mol 3.15 mol (80 g/mol) = 252 g Remember if “mol” is on top originally then inside the parenthesis it must go on the bottom. ­How many atoms are in 6.34 g of (NH 4 ) 3 PO 4 Answer: 3N + 12H + P + 4O = 149 /mol then 6.34 g (1 mole/149 g) = 0.0426 moles. then 0.0426 mol (6.022 x 10 23 formula units/ 1 mole) (20 atoms/1 formula unit) = 5.12 x 10 23 atoms.

8. PRACTICE PROBLEMS 1. What is the molar mass of Fe(NO 2 ) 3.6H 2 O 2. How many moles are contained in 750.0 g of Fe(NO 2 ) 3 ? 3. How many grams of iron are contained in 0.097 mol of Fe 2 (CO 3 ) 3 ? 4. How many atoms are contained in 25.0 g of nitrogen (N 2 )? 5. How many grams of potassium nitrite will contain 6.78 x 10 24 potassium atoms? 301.9 g/mol 3.868 mol 11 g 1.07 x 10 24 N-atoms 957 g