4. It is useful when counting objects, to define them in terms of a collective unit. For example, we use a dozen to mean 12 items. This makes it easier to count a large amount of items. It’s the same way with molecules, we cannot possibly count all the molecules or atoms in a substance. Instead we use a unit called the mole. What is a mole?

5. The Mole The mole is another term used to define a certain number of particles or atoms of a particular substance. 1 mole is defined as the number of atoms present in 12.00 grams of Carbon-12.

6. 1 mole = 6.02x10 23 particles 6.02x10 23 is known as Avogadro’s Number Relationship 1

8. Terminology… The particles can be defined as: - Molecules for covalent compounds and diatomic elements -Formula units for ionic compounds -Atoms for non-diatomic elements

9. How Big is a Mole? One mole of marbles would cover the entire Earth (oceans included) for a depth of three miles. One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 million times. It would take light 9500 years to travel from the bottom to the top of a stack of 1 mole of $1 bills.

10. 1 mole of Munchkins would cover the entire surface of the Earth and be 5 miles deep. (approx height of Mt. Everest) 1 mole of pennies could be distributed to the population of the Earth right now, and they could spent 1 million dollars, per hour, every day for the rest of their lives.

11. If you could count atoms at a rate of 10 million per second, it would take you 2 billion years to count 1 mole of atoms. A mole of rice grains would have the same mass as if every one of the 5 billion people on each had 1 million cars and we put them all on a scale.

12. Therefore, it is unbelievable that there is a mole of water molecules in 18 mL of water.

13. 1 mole of any substance has the same number of atoms/particles/molecules/formula units. Avogadro’s number is a constant, and does not change. However, the mass of 1 mole of a substance WILL change depending on the substance, because the composition changes.

14. While we know that a dozen always means 12 items… A dozen bricks has a much greater mass than a dozen feathers. The substance you are working with determines the mass of a “dozen”

16. COEFFICIENTS: Tell you how many moles of a compound you have. To find the total number of atoms, MULTIPLY the number of that particular atom you have by the coefficient.

17. Just like a dozen bricks has more mass than a dozen feathers… The mass of a mole of a substance is dependent on its composition (chemical formula / makeup) Relationship 2

18. To calculate the GFM, we add up the atomic masses of each atom in the formula and it is expressed in the unit grams/mole. (g/mol)

19. The mass of 1 mole of a substance is defined as its Gram Formula Mass. For example: 1 mole of O 2 has a mass of 32 grams. Therefore in 32 grams of O 2, there are 6.02x10 23 molecules (diatomic) For example: 1 mole of NaCl has a mass of 58 grams. Therefore in 58 grams of NaCl, there are 6.02x10 23 formula units (ionic)

20. Ex. Calculate the GFM of Na 3 PO 4 - 3 atoms of Na - 1 atom of P - 4 atoms of O x 23 g x 31 g x 16 g = 69 g = 31 g = 64 g + ---------- 164 grams

21. Name and Calculate the GFM for the following: CaSO 4 Na 3 P Mg(NO 3 ) 2 FeCl 3 (NH 4 ) 3 PO 4 Al 2 (PO 4 ) 3

23. Finally… There is also a relationship between 1 mole of a gas and the volume of a gas. This is known as Avogadro’s Hypothesis: 1 mole of a gas at STP = 22.4 L Relationship 3

24. 1 mol of a gas=22.4 L at STP Molar Volume at STP S tandard T emperature & P ressure 0°C and 1 atm Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

25. Molar Volume Timberlake, Chemistry 7 th Edition, page 268 1 mol of a gas @ STP has a volume of 22.4 L

26. Avogadro’s Hypothesis N2N2 H2H2 Ar CH 4 At the same temperature and pressure, equal volumes of different gases contain the same number of molecules. Each balloon holds 1.0 L of gas at 20 o C and 1 atm pressure. Each contains 0.045 mol or 2.69 x 10 22 molecules of gas.

27. Therefore: 1 mole = 6.02x10 23 atoms 1 mole = GFM of any cmpd or element 1 mole = 22.4 Liters of a GAS at STP CONVERSION FACTORS

28. Mass, Volume, Mole Relationship

29. Therefore, we can convert between these units use the factor label method. “The Mole Highway” GRAMS PARTICLESLITERS OF A GAS 1 mole GFM 6.02x10 23 22.4 “DIMO” Divide In Multiply Out

30. Recall the factor label method: When 2 things are equal to each other we can write them as a fraction, so long as there are UNITS!!!

31. Moles and Mass Moles and Volume Moles and Particles 1 molGFM or GFM 1 mol 22.4 L 1 mol 6.02x10 23 particles or

32. Example 1: How many grams are present in 4.5 moles of Sulfuric Acid Anytime you are talking about grams and moles, you must calculate the GFM of the compound. Formula of Sulfuric Acid = H 2 SO 4 GFM of Sulfuric Acid = 98 grams/mol

33. You must use factor label method to solve these problems! NO EXCEPTIONS!!! 4.5 moles x _________ =________grams g mol1 98441 GFM

34. Example 2: Calculate the number of moles in a 500 gram sample of MgCl 2 1. Calculate the GFM of MgCl2 –Mg: 1x 24 =24 94 g/mole –Cl: 2x 35 = 70 2. Use the factor label method to calculate the number of moles 500 grams x 1 mol = 5.3 moles 94 grams

35. Ex. 3 How many grams are present in 3.4 moles of NH 4 Cl? Calculate the GFM of Ammonium Chloride N: 1x 14 H: 4x 167 g/mole Cl:1 x 35 Use the factor label method to solve for grams –3.4 moles x 67 grams = 228 grams 1 mole

36. Example 4: How many atoms are present in 3.5 moles of NaCl? What conversion factor will we use to go from moles  atoms? 3.5 moles x __________________ = ____________ atoms Avogadro’s Number atoms mol 1 6.02x10 23 2.11x10 24

37. Ex 5: How many moles are found in 2.31x10 24 atoms? What value are we going to use for a conversion factor to go between moles and atoms? 2.31x10 24 atoms x ______________ = _______ moles mol atoms 1 6.02x10 23 3.81

38. Ex 6: How many moles of H 2 gas are there in 56L of H 2 gas at STP? What conversion factor are we going to use? 56 L x ___________ = _________ mol of H2 mol L 1 22.4 2.5

39. How many liters are there in 3.5 moles of N 2 gas at STP? 3.5 moles x ___________= _______ L mol L 1 22.478.4

40. How many atoms are there in 5.7x10 22 molecules of CO 2 ? Each molecule of CO 2 has _____ atoms 5.7x10 22 m’cules x ________ = ______________ atoms 3 3 atoms 1 molecule

41. How many molecules are there in 78 L of N 2 ? How can we convert from liters to molecules? 1. First – convert liters  moles 2. Moles  Molecules Solve:

42. How many atoms are there in 78L of N 2 ? How is this different than the last question? N 2 is a diatomic, which means that every molecule of N 2, is made up of 2 atoms of Nitrogen. * Solve

43. Example 10: How many atoms are there in a 15 gram sample of NaCl?

44. What is the volume of 3.00 grams of 0 2 at STP? 3.00x 1 mole = 0.09 mol of O 2 x 22.4 L = 32 g 1 mol 2.1 2.1liters

45. Gas Density and Molar Volume Since we know the volume and mass of a gas at STP, we can calculate the density Example: Calculate the density of CO 2 at STP –1 mole of a gas at STP = 22.4 L –1 mole of CO2 = 44 grams Density = mass volume Density = 44 grams = 22.4 L 1. 96 g/L 1. 96 g/L

46. Example The density of a gas is 1.96 g/L at STP. Calculate the molar mass. Key: Remember that molar mass is measured in g/mole, so that is the unit you want to end up with after factor label 1.96 g x = 1 liter 22.4 L 22.4 L 1 mole 1 mole 43.9 g/mole 43.9 g/mole

47. Example The density of a gas is 2.59 grams/liter at STP. Calculate the molar mass. Answer: 58.0 g/mol