Chapter8.ppt science 9*moleconceptslides
- 1. Chapter 8: The Mole Concept CHM 130 GCC Chemistry
- 2. Eggs come in dozens 12 eggs = 1 dozen Atoms come in moles 6.02 x 1023 atoms = 1 mole = NA NA is a ginormous number! How big is it? One mole of softballs would be the size of the Earth! 8.1 Avogadro’s Number and the Mole
- 3. Atoms are so tiny that one mole of atoms is about a handful. The mass of a mole of atoms = the atomic mass in grams on the Periodic Table. 1 mole of C atoms is 12.01 grams 1 mole of Na atoms is 22.99 grams What is the mass of one mole of Ne atoms? The Mole
- 5. 1. How many calcium atoms are in 0.250 moles of calcium? 2. Calculate the moles of 3.75 x 1027 molecules of oxygen gas? 6.02 x 1023 atoms or mlcls or 1 mol 1 mol 6.02 x 1023atoms or mlcls 0.250 mol Ca (6.02 x 1023 atoms/1 mol) = 1.51 x 1023 Ca atoms 3.75 x 1027 mlcls O2 (1 mol/6.02 x 1023 mlcls) = 6230 mol O2 8.2 Mole Calculations I: Avogadro’s Number
- 7. Molar mass tells us how much mass is in one mole of substance. Periodic Table masses are in units of (g/mol). Very important – the units are grams per 1 mole, not just grams How many grams in one mole of: carbon? gold? sodium? What do they all have in common? They all have 6.02 x 1023 atoms! 12.01 g/mol 196.97 g/mol 22.99 g/mol 8.3 Molar Mass
- 8. Calculate the molar mass of barium hydroxide. 1.What is the formula? 2.Add up the mass for every atom. Ba: 137.33 g/mol + O: 2 (16.00) g/mol + H: 2 (1.01) g/mol = 171.35 g/mol Ba(OH)2 Molar Mass
- 9. Use Molar Mass as (g/mol) or (mol/g) How many grams is 1.667 moles of oxygen gas? 1.667 mol O2 ( 32.00 g/mol) = 53.34 g O2 How many moles is 45 grams of silver? 45 g Ag ( mol/ 107.87 g) = 0.42 mol Ag How many grams is 0.0554 moles of water? 0.0554 mol H2O (18.02g /mol) = 0.998 g H2O 8.4 Grams to Moles (Mole Calcs II)
- 10. 8.5 Molar Volume (Volume of 1 mole of gas at STP)
- 11. Volume of 1 mole of gas Gases are mostly empty space so they ALL have the same volume despite different mass 22.4 L per 1 mole of any gas at STP STP is Standard Temperature and Pressure 0°C and 1 atm
- 12. For Gases only at STP: 22.4 L / 1 mol or 1 mol / 22.4 L What is the mass of 4.50 L of chlorine gas at STP? 4.50 L Cl2 (1mol / 22.4L) (70.90 g/mol) = 14.2 g Cl2 What is the volume of 1.25 moles of gas at STP? 1.25 mol ( 22.4 L / 1 mol) = 28.0 L gas
- 13. Density d = = me molar volu mass molar volume mass Calculate the density of ammonia gas, NH3, at STP. d = (17.04 g/mol ) / ( 22.4 L/mol ) = 0.761 g/L
- 14. 8.6 Mole Calcs III
- 15. Example How many grams does 17.35 liters of neon gas weigh at STP? How many atoms is this? 17.35 L = 15.6 grams Ne mol 1 g 20.18 L 22.4 mol 1 mol 1 atoms 10 x 6.02 L 22.4 mol 1 23 17.35 L = 4.66x1023 atoms Ne
- 16. 8.7 Percent Composition = mass % of each element in a compound You divide the total element molar mass by the total compound molar mass. % = (element / compound) x 100 %H = (2.02 g H / 18.02 g H2O) x 100 = 11.2% H %O = (16.00 g O / 18.02 g H2O) x 100 = 88.79% O
- 17. Example Problem Find the percent composition for TNT, C7H5(NO2)3 Total molar mass is 227.15 grams per mole % C = (84.07g / 227.15g) x 100 = 37.01% C % H = (5.05g / 227.15g) x 100 = 2.22%H % N = (42.03g / 227.15g) x 100 = 18.50%N % O = (96.00g / 227.15g) x 100 = 42.26%O
- 18. Try at home How many liters will 3.425 grams of carbon dioxide gas occupy at STP? 1.74 L How many molecules are in 3.425 grams of carbon dioxide? 4.68 x 1022 molecules What will be the mass of 3.0 x 1015 molecules of carbon dioxide? 2.2 x 10-7 grams
- 19. Self Test Page 248 Try 1-7, 10-13 Answers in Appendix J
- 20. Chapter 8 Quiz 1) How many molecules are in 1.25 g of copper? 2) What is the mass of 35.6 L of xenon gas at STP? 3) What is the mass percent of carbon in aspirin (C9H8O4)?