1. Moles GPS 13 -write 6.022 x 10^23 on the board
-ask: ever baked a cake? What if the recipe called for 6.02 x 10^23 individual crystals of sugar? Of course, that would be ridiculous. What do we use instead (cup)? So we have a unit of measurement when baking…we use cups, tablespoons, and teaspoons. Same thing in chemistry. I would never ask you to count out atoms of an element or ions/molecules in a compound. Not only is it ridiculous, it’s impossible to do with just your eyes alone. When we are talking about a huge amount of something, we use moles (which is 6.02 x 10^23 of something) to make our counting process much faster and easier. So, instead of saying I have 6.02 x 10^23 crystals of sugar, you can say I have exactly one mole of sugar.
- If you were to try to count out x 10^23 of something, how long to you think it would take? 4 generations.

2. The Mole: A unit of measurement
Moles are a unit of measurement much like other units of measurement you are familiar with. Examples of familiar units of measurement: 12 eggs = 1 dozen or 12 eggs/dozen 4 quarts = 1 gallon or 4 quarts/gallon 100 pennies = 1 dollar or 100 pennies/dollar 12 inches = 1 foot or 12 inches/foot

3. Moles: A unit of measurement
Moles can be used to express or to calculate the following: The number of particles in a sample The mass of a sample The volume of a gas (at 1 atm pressure, 0˚C)

4. Mole Map Moles Mass: grams Particles:
Molar Mass
grams/mole
Particles:
atoms, ions, formula units, molecules
Moles
6.02 x 1023 particles/mole
22.4
liters/mole
Gas Volume:
liters

5. Avogadro’s Number 602,000,000,000,000,000,000,000 particles = 1 mole
6.02 x 1023 particles / mole
1 mole of Cl atoms
6.02 x 1023 atoms of Cl

6. “Particles” include the following:
Water (H2O) Copper (Cu) Sodium Chloride (NaCl)
molecules atoms formula unit (boxed in) ions: Na+ and Cl-

7. Dimensional Analysis: Converting Units
Dimensional analysis: Using equivalencies to convert units for a substance Example: Convert 24 inches to feet (12 inches = 1 foot)

8. Dimensional Analysis: Converting Units
Examples: Convert 275 eggs to dozens (12 eggs = 1 dozen) Convert 2.75 dozen to eggs

9. Conversions: Particles and Moles
Example:
How many molecules of water are there in 3.0 moles of water?
- Work problem on board
1.8 x 1024 molecules of water

10. Conversions: Particles and Moles
Example:
How many moles of barium chloride are there in 9.28 x formula units of BaCl2?
1.54 x 1010 moles of BaCl2

11. Conversions: Particles and Moles
Example:
How many moles of magnesium are in 4.21 x 1023 atoms of magnesium?
0.699 moles of magnesium

12. Mole Map Moles Mass: grams Particles:
Molar Mass
grams/mole
Particles:
atoms, ions, formula units, molecules
Moles
6.02 x 1023 particles/mole
22.4
liters/mole
Gas Volume:
liters

13. Molar Mass 1 mole He = 4.0 g He 1 mole Cu = 63.5 g Cu 1 mole Hg =
200.6 g Hg
1 mole S =
32.1 g S

14. Molar Mass = grams/mole
Molar Mass (a.k.a. Formula Mass, Formula Weight, Molecular Weight)
the mass of one mole of a given compound or element
Molar Mass = grams/mole
The molar mass of an element is simply its average atomic mass with grams/mole as units
Example:
Find the molar mass of Nitrogen
- Notice that in all of the previous problems, you were given the amount of substance in moles. However, most of our measurements in chemistry are in grams. Therefore, you must be able to convert from grams to moles using molar mass.
14.0 g/mol

15. Conversions: Grams and Moles
Example:
How many moles of sodium are in grams of sodium?
- work problem on board
2.45 mol Na

16. Molar Mass of a Compound
17.04 g/mol

17. Molar Mass of a Compound
1 mole of water, H2O, on the balance
18.0 g of water = 1 mole of water

18. Molar Mass of a Compound
Molar mass of a compound: use “SSMT” chart
Example: Find the molar mass of K2S
S S M T
*multiply across, add down total column
Symbol
Subscript
Molar mass
Total K x =
78.2 S x =
32.1 +
110.3 g/mol

19. Molar Mass of a Compound
Determine the molar mass for the following:
Na2CO3
Pb(NO3)2
106.0 g/mol
- Molar mass is a bit more complex for compounds….must add up the atomic mass for each atom of each element present in the compound.
- do SSMT charts for each on the board
331.2 g/mol

20. Conversions: Grams and Moles
Example:
What is the mass (in grams) of 1.50 mole of potassium sulfate?
261 grams of K2SO4

21. Conversions: Grams and Moles
Example:
How many moles of copper (II) nitrate are in 544 grams of Cu(NO3)2?
2.90 moles of copper (II) nitrate

22. Mole Map Moles Mass: grams Particles:
Molar Mass
grams/mole
Particles:
atoms, ions, formula units, molecules
Moles
6.02 x 1023 particles/mole
22.4
liters/mole
Gas Volume:
liters

23. Conversions: Particles and Grams
There is no single conversion factor between particles and grams.
You must always convert to moles first.

24. Conversions: Particles and Grams
Example:
How many atoms of Cu are in grams of Cu?
121.5 g Cu mol Cu x 1023 atoms Cu =
63.5 g Cu mol Cu
1.15 x 1024 atoms Cu

25. Conversions: Particles and Grams
Example:
How many molecules of water are present in 39 grams of water?
1.3 x 1024 molecules of water

26. Conversions: Particles and Grams
Example:
How many grams of gold are there in 4.21 x 1023 atoms of gold?
138 grams of gold

27. Mole Map Moles Mass: grams Particles:
Molar Mass
grams/mole
Particles:
atoms, ions, formula units, molecules
Moles
6.02 x 1023 particles/mole
22.4
liters/mole
Gas Volume:
liters

28. Molar Volume of a Gas Molar Volume = 22.4 L/mol Molar volume of a gas:
The volume of one mole of a gas at standard temperature and pressure
STP:
temperature = 0ºC pressure = 1 atmosphere
- Think about a balloon filled with 22.4 liters of helium. If the temperature is zero celcius and the pressure is one atmosphere, then that would be exactly one mole of helium.

29. Molar Volume of a Gas

30. Conversions: Liters and Moles
Example
How many moles of any gas are present in 12.5 liters of any gas at STP?
0.558 moles of gas

31. Conversions: Liters and Grams
Example
How many grams of He gas are present in 82 liters of He gas at STP?

32. Conversions: Liters and Particles
Example
How many liters of CO2 gas are present in
2.1 x 1025 molecules of CO2 gas at STP?

33. Percent Composition
The percentage of mass that each element contributes to the total mass of the compound
% Comp. = Molar mass of element x 100
Molar mass of entire compound
Example: Percent composition of Water
11%H
- fruit salad analogy
89% O

34. Percent Composition Symbol Subscript Molar mass Total K 2 x 39.1 ==
78.2 S x =
32.1 +
110.3 g/mol
% K = 78.2 / x 100 = 70.9% K % S = 32.1 / x 100 = 29.1 % S

35. Percent Composition % Al = 15.8 % % S = 28.1 % % O = 56.14 %
Example: Find the percent composition for each element in Al2(SO4)3
- work problem on board
% Al = %
% S = %
% O = %

36. Empirical Formula
The empirical formula for a compound represents the smallest whole number molar ratio of elements in that compound
two moles hydrogen one mole oxygen
Empirical Formula from Mass (grams) of Elements:
1. Convert each element’s mass to moles
2. Divide by the smallest number of moles
3. Round to the nearest whole number and use as subscripts
H2O

37. Empirical Formula Na2SO3 Example:
Determine the empirical formula for a compound containing 36.5 grams of sodium, 25.4 grams of sulfur, and 38.1 grams of oxygen.
Na2SO3 16

38. Empirical Formula
Example: What is the empirical formula for a compound that has g of carbon, g hydrogen, and g of nitrogen?
- work example on board
CH5N

39. Empirical Formula from Lab Data
An iron chloride sample was reacted with excess lead in order to determine the formula of the iron chloride. Determine the formula for the iron chloride compound.
Mass (grams)
Initial mass of iron chloride
4.89 g
Mass of solid iron produced
1.30 g

40. Empirical Formula from % Composition
Same procedure, however start by assuming 100 g sample.
Why assume 100g sample? It makes for easier math!
Sucrose C12H22O11
- the percentage composition for each element will remain the same no matter the sample size, so 100 g is picked for easier calculations

41. Empirical Formula from % Composition
Example: What is the empirical formula for a compound that has a percent composition of 40.0% carbon, 6.71% hydrogen, and 53.3% oxygen?
CH2O

42. Molecular Formula from Empirical
Example: If the empirical formula for a compound is CH2Cl and the molar mass for the molecular formula is g/mol, what is the molecular formula? empirical molecular CH2Cl ? 49.5 g/mol g/mol / 49.5 = 2 Molecular twice as massive as empirical
Find using “SSMT”
Molecular
C2H4Cl2

43. Molecular Formula from Empirical
Example: If empirical formula for a compound is CH2O and the molar mass of the molecular formula is g/mol, what is the molecular formula?
molecular = C3H6O3

44. Empirical Formula: Hydrates
Hydrate: a compound that contains water molecules within its crystalline structure Example: Copper(II) sulfate pentahydrate
5 water molecules within crystal
SO42-
CuSO4 • 5H2O
H2O
Cu2+

45. Empirical Formula: Hydrates
Heating a hydrate produces water vapor and anhydrous salt Lab simulation:

46. Empirical Formula: Hydrates
In a hydrate, the coefficients represent the mole ratio between the anhydrous salt and the water:
one mole CuSO five moles H2O
Empirical Formula for a Hydrate:
1. Determine the mass of water and mass of anhydrous salt
2. Convert each mass to moles
3. Divide by the smallest number of moles
4. Round to the nearest whole number and use as subscripts
CuSO4 • 5H2O

47. Empirical Formula: Hydrates
Example:
A 9.87 gram sample of BaCl2 • __H2O is heated. After it is heated completely, the sample now has a mass of grams. Find the empirical formula for the hydrate.
/ = 2.99
/ = 1
BaCl2 • 3H2O

48. Empirical Formula: Hydrates
Example:
A gram sample of FeCl3 • __H2O is heated. After it is heated completely, the sample now has a mass of grams. Find the empirical formula for the hydrate.

49. Hydrate Formula from Lab Data
A student is assigned the task of determining the number of moles of water in one mole of MgCl2• n H2O. The student collects the data shown below: Determine the formula for the hydrate.

50. SOL covered during lesson
CH 4 a, b
CH 3 c

51. Extra Slides

52. Empirical/Molecular Formula
Example: Caffeine has a percent composition of 49.48% carbon, 5.15% hydrogen, 28.87% nitrogen, and 16.49% oxygen. If the molar mass of the compound is g/mol, what is the molecular formula of caffeine?
C8H10N4O2

53. Empirical Formula empirical = CH2Cl molecular = C2H4Cl2
Example: What is the empirical formula for a compound that has a percent composition of 71.65% chlorine, 24.27% carbon, and 4.07% hydrogen? If the molar mass for the molecule is g/mol, what is the molecular formula?
empirical = CH2Cl
molecular = C2H4Cl2

54. Empirical/Molecular Formula
Example: What is the empirical formula for a compound that has a percent composition of 40.0% carbon, 6.71% hydrogen, and 53.3% oxygen? If the molar mass of the compound is g/mol, what is the molecular formula?
empirical = CH2O
molecular = C2H4O2

55. The Mole
Two-step problems:
Example:
How many atoms of oxygen are in 3.9 moles of carbon dioxide?
- recall: smallest units of elements are atoms, of covalent compounds are molecules, of ionic compounds are ions or formula units (draw chart)
4.7 x 1024 atoms of O

56. The Mole
Example
How many hydroxide ions are there in moles of Mn(OH)3?
2.38 x 1025 hydroxide ions