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# Chapter 10 Notes

Chapter 10 Notes. Mole Representative Particles Molecular Mass (mm) - gam used for atoms - gmm used for molecules - gfm used for formula units Mole Volume Mixed Mole Conversions. The Mole. A dozen is a counting number that means 12. The mole is a counting number.

## Chapter 10 Notes

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1. Chapter 10 Notes Mole Representative Particles Molecular Mass (mm) - gam used for atoms - gmm used for molecules - gfm used for formula units Mole Volume Mixed Mole Conversions

2. The Mole • A dozen is a counting number that means 12. • The mole is a counting number. • A very large number, but still, just a number. • 6.02 x 1023 of anything is a mole or mol • Items that we count with the mole are called representative particles • They are: atoms, ions, molecules and formula units

3. Moles to representative particles How many atoms of carbon will it take to have 1.237moles of C? 1.237mol C x = 7.44674x1023 = 7.447x1023atom C (6.02x1023atoms) = 1 mol

4. Representative particles to moles How many mole are there in 4537.8 molecules of methane CH4? 4537.8 molec. CH4 x = 7.53787375x10-21 = 7.5379x10-21 mol CH4 1mole = (6.02x1023molecules)

5. Molar mass • 12.0 grams of C-12 contains a mole of atoms. • Makes the mass numbers on the periodic table the mass of the average atom. • Mass of 1 mole of a substance. • Often called molecular weight.

6. Molar mass • To determine the molar mass of an element, (gam) look on the table. • To determine the molar mass of a molecular compound, (gmm) add up the molar masses of the elements that make it up. • To determine the molar mass of a ionic compound, (gfm) add up the molar masses of the elements that make it up.

7. Find the molar mass of Li: Since this is an atom (gam) Look up on the periodic table & find the mass of Li: 6.941grams/mole For convenience sake, we round to the tenths place for a mass of 6.9 grams/mol

8. Find the molar mass of O2: Since this is an molecule (gmm) Look up on the periodic table & find the mass of O: 15.999 grams/mole For convenience sake, we round to the tenths place for a mass of 16.0 grams/mol Since there are two oxygen atoms in O2 we must have the mass of two oxygens or 2 x 16.0g = 32.0 g

9. Find the molar mass of CH4: Since this is an molecule (gmm) Look up on the periodic table & find the mass of C: 12.011 grams/mole => 12.0g/mol Look up on the periodic table & find the mass of H: 1.0079 grams/mole => 1.0g/mol Since there are four hydrogen atoms in CH4 we must have the mass of four hydrogens; 4 x 1.0g = 4.0 g Add the masses 12.0g/mol + 4.0g/mol = 16.0 g/mol

10. Find the molar mass of Mg3P2: For ionic compounds use (gfm) Look up on the periodic table & find the mass of Mg: 24.305 grams/mole => 24.3g/mol Look up on the periodic table & find the mass of P: 30.974 grams/mole => 31.0g/mol Since there are three magnesium atoms in, we must have the mass of 3 Mg; 3 x 24.3g = 72.9 g Since there are two phosphorus atoms in, we must have the mass of 2 P; 2 x 31.0g = 62.0g Add the masses 72.9g/mol + 62.0g/mol = 134.9 g/mol

11. Find the molar mass of Mg(NO3)2: For ionic compounds use (gfm) Look up on the periodic table & find the mass of Mg: 24.305 grams/mole => 24.3g/mol Look up on the periodic table & find the mass of NO3: 14.0g + 3 x (16.0g) = 62.0g/mol Since there are two nitrates we must have the mass of two nitrogen and six oxygen atoms: 2 x (NO3) or 2 x 62.0g = 124.0g/mol Add the masses 24.3g/mol + 124.0g/mol = 148.3 g/mol

12. Find the molar mass of Al2(Cr2O7)3: For ionic compounds use (gfm) Look up & find the mass of : Aluminum, Chromium & Oxygen: 2 x Al = 2 x 27.0g = 54.0g 6 x Cr = 6 x 52.0g = 312.0g 21 x O = 21 x (16.0g) = 336.0g/mol Add all the masses: 54.0g/mol + 312.0g/mol + 336.0 g/mol = = 702.0g/mol

13. Find the molar mass of CaSO4 · 2H2O : For ionic compounds use (gfm) Look up & find the mass of : Calcium, Sulfur, Oxygen: Ca = 40.1 and S = 32.1 = 72.2g 4 x O = 4 x (16.0g) = 64.0g Water for the Hydrated compound: H2O = (2 x 1.0g) + 16.0g = 18.0 g 2(H2O) = 2 x 18.0g = 36.0g 72.2g/mol + 64.0g/mol + 36.0 g/mol = 172.2g/mol

14. Mass to mole conversions 24.3g of O2 is how many moles of O2? If you want to convert between moles and grams you need a molar mass Remember O2 = 2 x 16.0g = 32.0 g 24.3g O2 x 1 mole O2 = 32.0 g O2 = 0.759375 mole O2 => 0.759 mole O2

15. Moles to mass conversion 1.758 moles of Mg(NO3)2 is how many grams? If you want to convert between moles and grams you need a molar mass Remember: 148.3 g/mol 1.758mol x 148.3g = 1mol = 295.8714g => 295.9g Mg(NO3)2

16. Mole to volume conversion The volume of a mole of any gas at (STP) standard temperature and pressure is 22.4L or 1mol = 22.4L What volume would 3.4moles of CH4 occupy? 3.4mol CH4 x 22.4L = 1mol 76.16L => 76L

17. Volume to mole conversion 487.2L of CO2 are produced by one car in a year. How many moles of CO2 is that? 487.2L CO2 x 1mole = 22.4L = 21.75mol CO2

18. Using DA for multi step conversions How many grams are there in 100.0 Liters of Helium? We don’t know a mass to volume conversion. But, we do know that they can both be related to the mole. 100.0L He x 1mol x 22.4L 4.0g = 1mol = 17.85714g = 17.86g He

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