Moles and Molar Mass Chemistry

1. Moles and Molar MassChemistry

2. Learning Objectives • TLW define and use the concept of a mole (TEKS 8.A) • TLW use the mole concept to calculate the number of atoms, ions, and molecules in a sample of material (TEKS 8.B) • TLW manipulate chemical quantities using dimensional analysis (TEKS 2.G)

3. Background • As you might imagine, we will not be able to measure the mass or volume of individual atoms, ions, or molecules in the Chemistry Lab.   • Molecules are so small that a single drop of water contains billions and billions of them.  • Just like eggs are grouped in dozens, and other items are grouped in grosses, reams, etc… atoms and molecules are grouped in moles.  (not be confused with the fury little creature that lives underground) • We may not be able to measure the mass of one water molecule in lab, but we can measure the mass of one mole of water molecules.

4. Mole Day Song • Link to YouTube

5. A. What exactly is a mole? 1. A counting number 2. The SI unit for amount of particles 3. Like all units, a mole has to be based on something reproducible. A mole is the quantity of anything that has the same number of particles found in 12.000 grams of carbon-12 4. 1 mol = 6.022 X 1023 items (atoms, ions, molecules) 5. Referred to as Avogadro’s Number

6. How large is large? Mole Analogies 1 mole of basketballs would fill a bag the size of the earth!! Counting every grain of sand in the desert!!

7. A mole of marshmallows would cover the planet Earth 12 miles high • Computers can count at the rate of over 800 million counts per second.  At this rate it would take a computer over 25 million years to count to 6.02 x 1023 • 1 mole of marbles would fill the entire Grand Canyon and there would still be enough left over to displace all the water in Lake Michigan and a few other lakes! 

8. A mole of hockey pucks would be equal to the mass of the Moon. • Assuming that each human being has 60 trillion body cells (6.0 x 1013) and the Earth's population is 6 billion (6 x 109), the total number of living human body cells on the Earth at the present time is 3.6 x 1023 or a little over half of a mole.

9. Activity for Mole Concept • Link

10. Activity Follow up Discussion • If one mole of pennies were divided up among the Earth's population of 6 billion people, each person would receive 1 x 1014 pennies = 1 x 1012 dollars ($1 TRILLION dollars) • Personal spending at the rate of one million dollars a day would use up each person’s wealth in about 2,740 years.  • If you have 6.022 x 1023 pennies and you spend $1 million dollars each day it would take you 1.65 x 1012 years to spend all • Life would not be comfortable because the surface of the Earth would be covered in copper coins to a depth of nearly 900 meters (nearly 9 football fields deep).

11. B. Molar Mass 1. The mass of 1 mole of a pure substance is called the molar mass (see periodic table) 2. Atomic mass tells a. atomic mass units per atom (amu) b. grams per mole (g/mol)

12. 3. Molar mass is usually rounded to two decimal places 4. Ex. of Molar mass carbon 12.01 g/mol aluminum 26.98 g/mol zinc 65.39 g/mol 5. A molar mass of an element contains 1 mole of atoms carbon’s mole’s mass is 12.01g

13. 6. MOLAR MASS EQUALS ATOMIC MASS C. What about the molar mass of molecules and compounds? 1. Water – H2O molar mass: 2(1.01) + 16.00 = 18.02 g/mol

14. 2. Sodium chloride = NaCl molar mass: 22.99 + 35.45 = 58.44 g/mol 3. sucrose = C12H22O11 molar mass: 12(12.01) + 22(1.01) + 11(16.00) = 342.34 g/mol

15. D. Molar Conversions 1. How many moles of carbon are in 26 g of carbon? 26 g 1 mol C = 2.2 mol C 12.01 g C The molar mass of Carbon

16. 2. How many molecules are in 2.50 moles of C12H22O11? 2.50 mol 6.022  1023molecules 1 mol = 1.51  1024 molecules of C12H22O11

17. 3. How many grams in 3.7 moles of Silicon? 3.7 mol Si 28.09 g Si = 103.93 g Si 1 mol Si

18. 4. How many moles are in 15 g of H2O? …..1st find the molar mass of H2O = 2(1.01) + 16.00 = 18.02 g per mole H2O H = 1.01 g/mol O = 16.00 g/mol 15g 1 mol = .83 mol H2O 18.02 g

19. Group Practice 1. a) 20.0 g of Fe equals ___ moles b)19.7 g of Mg equals ___ moles 20.0 g Fe 1 mol = .36 mol Fe 55.85 g Fe 19.7 g Mg 1 mol = .81 mol Mg 24.31 g Mg

20. Group Practice 2. a) 100.0 g of FeCl equals ___ moles b)40.00 g of CO2 equals ___ moles 100.0 g 1 mol = 1.10 mol FeCl 91.30 g FeCl 40.00 g 1 mol = .91 mol CO2 44.01 g CO2

21. 0.356 mol 26.98 g Al = 9.60 g Al 3. a) 0.356 moles of Al is how many g? b) 0.56 moles of Ne is how many g? 1 mol 0.56 mol 20.18 g Ne = 11.30 g Ne 1 mol

22. 0.50 mol 101.96 g Al2O3 = 50.98 g Al2O3 4. a) 0.50 moles of Al2O3 is how many g? b) 2.6 moles of HF is how many g? 1 mol 2.6 mol 20.01 g HF = 52.03 g HF 1 mol

23. 0.50 mol 6.022 x 1023 molecules 5. a) 0.50 moles of Na is how many molecules? b) 2.1 moles of HF is how many molecules? = 3.01 x 1023 molecules 1 mol 2.1 mol 6.022 x 1023 molecules = 1.26 x 1024 molecules 1 mol

24. 1 mol 4.5 x 1024 molecules = 7.5 moles Cr 6. a) How many moles are in 4.5 x 1024 molecules of Cr? b) How many moles are in 3 x 1026 molecules of Cr2O3? 6.022 x 1023 molecules 1 mol 3 x 1026 molecules = 498 moles Cr2O3 6.022 x 1023 molecules

25. 6.022 x 1023 molecules 1 mol 30.1 g Cr = 3.49 x 1023 molecules Cr 7. a) How many molecules of Cr are in 30.1 g? b) How molecules of Fe2O3 in 2,500 g? 1 mol 52.00 g 6.022 x 1023 molecules 2,500 g 1 mol = 9.43 x 1024 molecules Fe2O3 159.70 g 1 mol

26. Factoid to Remember • Subscripts indicate moles H2 • When we move to balancing chemical equations moles = coefficients 2H2 + O2 2H2O

27. Independent Practice • Calculations – Set 1 • Calculations – Set 2