1. 7.1 Notes Continued…The Mole! Key Concepts Why do chemists use the mole? How can you calculate the mass of a reactant or product in a chemical reaction?

2. The counting _________ you use depends on what you are counting Counting with Moles For example… shoes are often counted by the __________ eggs by the ______________ paper by the ____________ unit pair dozen ream

3. Chemists also need practical units for counting things Why is it difficult for chemists to actually count atoms or molecules? They are too small and numerous

4. Chemists make use of a unit called the ___________ to count large numbers of small particles The mole is abbreviated ________ The number of particles in one mole is ALWAYS _______________...this number is called ______________ constant If you write out Avogadro’s number, it looks like this. 602 000 000 000 000 000 000 000 mole mol 6.02 x 10 23 Avogadro’s

5. The volume occupied by one mole of different substances ___________ because the size of different ____________ are ______________ varies particlesdifferent

6. The average atomic mass shown for each element on the periodic table also represents the mass in _________ for one _______ of each element The mass of 1 mole of a pure substance is called ___________ ________ So, how many sodium atoms are in one mole? What is their molar mass? grams mole molarmass 6.02 x 10 23 atoms 22.99 g/mol

7. To find the molar mass of a single element, simply write down the mass shown on the periodic table, followed by the unit _________ Practice! Determine the molar mass of… Iron, Fe Copper, Cu Neon, Ne Molar Mass of an Element g/mol 55.85 g/mol 63.55 g/mol 20.18 g/mol

8. To find the molar mass of a ___________ element, such as O 2, multiply the mass shown on the periodic table by ______ because two atoms are present in the _________ Practice! Oxygen, O 2 Hydrogen, H 2 Fluorine, F 2 Molar Mass of a Diatomic Element diatomic 2 formula 16.00 x 2 = 32.00 g/mol 1.01 x 2 = 2.02 g/mol 19.00 x 2 = 38.00 g/mol

9. To find the molar mass of a compound, such as MgCl 2, multiply the mass shown on the periodic table for each element by the ___________ shown; then ______ your total together Practice Magnesium chloride, MgCl 2 Aluminum oxide, Al 2 O 3 Molar Mass of a Compound subscriptadd 24.31(35.45 x 2)= 95.21 g/mol (26.98 x 2)(16.00 x 3) + += 101.96 g/mol

10. Moles to Mass To convert from a given number of moles to the mass of a substance, follow these steps… 1.Write down the __________ # of moles in the problem. 2.Multiply by the __________ __________ given on the _____________ table; make sure that one mole is on the _______________ of the conversion factor so that the mole ___________ out 3.Record the mass of your substance in __________ given # of moles x __________ = mass of the substance mass from periodic table 1 mole given molarmass periodic bottom cancels grams

11. Practice Problem…Moles to Mass Determine the mass in grams of 3.50 mol of copper (Cu). Chapter 3 3.50 mol Cu x ______________ 1 mol Cu g Cu = 222 g Cu 63.55

12. Mass to Moles To convert from a given mass of a substance to its number of moles, follow these steps… 1.Write down the __________ mass in the problem. 2.____________ by the molar mass given on the _____________ table; make sure that one mole is on the _____________ of the conversion factor because it is the ____________ unit 3.Record the ___________ of _________ of the substance given mass x __________ = # of moles substance mass from periodic table 1 mole given Divide periodic top desired numbermoles

13. Practice Problem…Mass to Moles Calculate the number of moles in 0.850 g of hydrogen atoms (H). 0.850 g Hx __________ g H 1 mol H 1.01 = 0.842 mol H

14. Review Question 1 How many particles are always contained in one mole? 6.02 x 10 23

15. Review Question 2 What conversion factor would complete the problem below? # moles x ____________ = grams of a substance 1 mol Molar mass

16. Review Question 3 What conversion factor would complete the problem below? grams of a substance x ____________ = # of moles molar mass 1 mole