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# Chapter 10 notes

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mole conversions, dimensional analysis, Chapter 10 notes for chemistry B class

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### Chapter 10 notes

1. 1. Chapter 10 Notes All About the Mole
2. 2. Objectives • Convert a quantity of a chemical between moles, mass (g), particles, and volume. • Calculate the molar mass for any compound. Hi, I’m Monty Mole. I’ll be your guide for this unit…. The evil monkey from the closet has the day off….
3. 3. Molar Mass Step 1: Find each atom on the periodic table. Step 2: Find out how much each atom weighs. (atomic mass) Step: 3 Multiply the mass by the number of atoms in the molecule. Step 4: Add them all up! Try it out! Find the molar masses of the following: NaCl, SO3, H2O, PCl3
4. 4. NaCl 58 g/mol SO3 80 g/mol H2O 18 g/mol PCl3 136 g/mol
5. 5. What is a Mole? •A mole is a measurement of matter. •It is used for counting things that require large numbers. •The mole is just another unit of measure like feet or grams. The number that we use to equal a mole is called Avogadro’s number. This number is 6.02 X 1023
6. 6. Everything Goes Through The Mole! • To convert from one unit to another, you must use the mole as an intermediate step. •In other words…you might need a “two-step” conversion problem.
7. 7. What is a “Two-Step” Conversion Problem? • Two conversion factors –One to convert from given unit to moles –One to convert from moles to wanted unit
8. 8. Mole Road Map (4 LIFE) Mass Representative Particles Mole 22.4L 1mol 1mol 22.4L 1 m ol 6.02x10 23 particles M olar m ass 1 m ol 1 m ol M olar m ass 6.02x1023 particles 1 m ol (grams) (atoms, molecules, or formula units) Volume of gas (STP)
9. 9. Here’s An Example Calculate the number of molecules in 60.0 g NO2. Given: 60.0 g NO2 1st Conversion: Molar Mass Equality molar mass NO2 : 46.01 g 46.01 g = 1 mol 2nd Conversion: Definition of Mole Equality 1 mol = 6.02 x 1023 molecules
10. 10. So here’s the equation: 60.0 g NO2 x 1 mol x 6.02 x 1023 molecules = 46.01 g NO2 1 mol 7.85 x 1023 molecules NO2
11. 11. Another Example Calculate the volume, in liters, of 3.24 x 1022 molecules of Cl2 (STP). 1.21 L Cl2 3.24 x 1022 molecules Cl2 x 1 mol x 22.4 L Cl2 = 6.022 x 1023 molecules 1 mol
12. 12. Now let’s practice!!! HAAA AAHAHAAAA! How many moles is 2.80 X 1024 atoms of silicon? How many moles is 2.17 X 1023 particles of bromine? How many moles are in 20 grams of NaCl? Determine the volume in liters of 5 moles of hydrogen gas.
13. 13. Warm Up! • How many moles are in 100 grams of water?
14. 14. Calculating Percent Composition • Step 1: Find the atomic mass of each element in the compound from the periodic table. • Step 2: Multiply each mass by the number of atoms in the compound. • Step 3: Add all the numbers together. • Step 4: Divide each individual number by the total weight and multiply by 100.
15. 15. Let’s practice! • Find the percent composition of PbCO4 Pb 207 1 207 C 12 1 12 O 16 4 64 283 total weight 207/283=.73 Or 73% 64/283=.23 or 23% 12/283=.04 or 4%
16. 16. Percent Composition • When no formula is given, take the numbers that are given and add them together to get a total. • Divide each number by the total and multiply by 100 to get the percent.
17. 17. Empirical Formula • What is an empirical formula? • This is a formula that gives the lowest whole number ratio of atoms in a compound. • It’s similar to reducing fractions.
18. 18. Calculating Empirical Formulas • Step 1: Start with the number of grams of each element in the compound. If it is a percent, then the percent equals the mass. • Step 2: Convert each mass to moles. Use what you know about conversions. (Hint: You are dividing by the atomic mass from the periodic table!)
19. 19. • Step 3: Divide by the LOWEST number. • Step 4: If you get a number that’s too far to round, multiply every number to get a whole number. • Step 5: The number for each element equals the number in the formula.
20. 20. Molecular Formula • Molecular formula is similar to empirical formula. • It is a multiple of the empirical formula and reflects the actual chemical formula. • Step 1: If the empirical formula isn’t given, calculate this first. • Step 2: Find the molar mass of the empirical formula.
21. 21. • Step 3: Using the molecular mass given, divide the empirical formula’s weight by the molecular mass. • Step 4: Multiply that answer into the empirical formula.
22. 22. Science SWAG Bring me 1 mole of something! You must prove it!