1. The Mole: Avogadro’s number

2. How much is:
A dozen?
A century?
A mole?

3. Can you count a mole of pennies?
If you could count 5 per second, it would take you
6.02 x ÷ 5 pennies/second ÷ 60 sec/min ÷ 60 min/hr ÷ 24hrs/day ÷ 365 days/yr =

4. Can you spend a mole of dollars?
If you could spend $1,000,000 every second it would take you
6.02 x ÷ $1,000,000/sec ÷ 60 sec/min ÷ 60 min/hr ÷ 24hrs/day ÷ 365 days/yr =

5. When measuring amounts, you can count or you can mass them.
If I want 2 dozen baseballs, I can count baseballs
Or I can mass of baseballs.

6. Since we can’t count a mole of atoms, we MUST mass chemicals to measure moles
6.02 x atoms of sulfur
32.07 grams of sulfur
6.02 x atoms of carbon
12.01 grams of carbon

7. How do we measure moles?
mole = number of particles equal to the number of atoms in 12 g of C-12
1 atom of C-12 weighs exactly
1 mole of C-12 weighs exactly
The number of particles in 1 mole is called ____________ Number = x 1023
1 mole of C atoms weighs and has
atoms
the average mass of a C atom is amu

8. How do we measure moles?
The atomic mass on your periodic table is the mass of a mole of atoms of that element.
What is the mass of a mole of copper atoms?
So, to count 6.02 x 1023 copper atoms, we mass out on the scale.

9. Mole and Mass Relationships
Sulfur
32.06 g
1 mole
Carbon
12.01 g

10. Find the mass of: A mole of silicon atoms
6.02 x 1023 atoms of nitrogen
6.02 x 1023 atoms of sodium
2 moles of sodium atoms

11. How many atoms are in: A mole of silicon 14.01 g of nitrogen
2 moles of sodium
45.98 g of sodium

12. How many things are in: A mole of footballs A mole of water
2 moles of pencils
½ mole of lead

13. Molar mass is the mass of one mole of a substance
To find the molar mass of an element, look on the periodic table.
To find the molar mass of a compound, add all the masses of its elements

14. Chemical Formulas as Conversion Factors
1 spider  legs
1 chair  legs
1 H2O molecule  H atoms & O atom

15. Molar Mass of Compounds
the relative weights of molecules can be calculated from atomic weights
Formula Mass = 1 molecule of H2O
since 1 mole of H2O contains 2 moles of H and 1 mole of O
Molar Mass = 1 mole H2O

16. Find the molar mass of: Ammonium phosphate NH4+ PO43- (NH4)3PO4 =
Carbon dioxide
CO2

17. Find the molar mass of:
Hydrogen gas H2 =
Elemental hydrogen H

18. Find the molar mass of: Iron Fe = Iron (III) hydroxide Fe3+ OH-

19. Converting to and from moles.
To convert between moles and particles, simply multiply or divide by Avogadro’s number.
2 mol x (6.02 x 1023 particles/mol) = 1.20 x 1024 particles
3.1 x 1024 particles x (1 mol/ 6.02 x 1023 particles) = 5.0 mol

20. Remember unit factors?

21. Converting to and from moles.
Converting between moles and mass requires the molar mass of the substance from the periodic table.
Element: Ag = g/mol
Ionic compound: CaCl2 = g/mol
Covalent compound: NO2 = g/mol
Always keep at least two decimal place on all values taken from the periodic table.

22. Converting to and from moles.
To convert from moles to grams, multiply by molar mass:
0.500 mol H2O x (18.0g/mol) =
9.00g H2O
To convert from grams to moles, divide by molar mass:
54g H2O x (1mol/18.0g) =
3.0 mol H2O

23. Converting to and from moles.
For gases, use the fact that at STP, 1 mol of any gas has a volume of Liters.
What is STP?
Standard Temperature = K or °C
Standard Pressure = atmosphere =
mm Hg (barometric) = kPa.

24. Converting to and from moles.
To go from moles to volume, multiply by 22.4L.
3.00 mol x (22.4L/mol) = of gas
To go from volume to moles, divide by 22.4L
44.8L x (1mol/22.4L) = moles of gas

25. Converting to and from moles.
A convenient tool for making these conversions is called a “mole map.”
With the mole at the center, we can put all of the aforementioned calculations together into one simple picture.

26. The Mole Map
Gas STP
# Particles
Mole
Mass

27. Percent Composition Percentage of each element in a compound By mass
Can be determined from
the of the compound
the experimental mass analysis of the compound
the total mass of
The percentages may not always total to 100% due to

28. What percentage of water is Oxygen?
Formula of the compound
Mass of the compound
Mass of each element

29. Mass Percent as a Conversion Factor
the mass percent tells you the mass of a constituent element in 100 g of the compound
the fact that NaCl is 39% Na by mass means that 100 g of NaCl contains 39 g Na
this can be used as a conversion factor
100. g NaCl  39.0 g Na

30. Empirical Formulas
The simplest, whole-number ratio of atoms in a molecule is called the
can be determined from percent composition or combining masses
The Molecular Formula is a multiple of the Empirical Formula
% A mass A (g) moles A
100g MMA
% B mass B (g) moles B
100g MMB
moles A
moles B

31. Empirical Formulas Hydrogen Peroxide Molecular Formula = H2O2
Empirical Formula = HO

32. Benzene
Molecular Formula =
Empirical Formula =
Glucose
Molecular Formula =
Empirical Formula =

33. Finding an Empirical Formula
convert the
skip if already grams
convert
use molar mass of each element
divide all by
round or multiply all mole ratios by number to make all whole numbers
if ratio ?.5, multiply all by 2; if ratio ?.33 or ?.67, multiply all by 3, etc.
skip if already whole numbers

34. Determine the empirical formula of a compound containing 80
Determine the empirical formula of a compound containing 80.0 grams of carbon and 20.0 grams hydrogen.

35. Grams to moles

36. Divide by smallest

37. Write Empirical Formula

38. Example:
A laboratory analysis of aspirin determined the following mass percent composition. Find the empirical formula.
C = 60.00%
H = 4.48%
O = 35.53%

39. All these molecules have the same Empirical Formula
All these molecules have the same Empirical Formula. How are the molecules different?
Name
Molecular
Formula
Empirical
glyceraldehyde
C3H6O3
CH2O
erythrose
C4H8O4
arabinose
C5H10O5
glucose
C6H12O6

40. Molecular Formulas The molecular formula is a multiple of
To determine the molecular formula you need to know and the of the compound

41. What is the molecular formula for ethane if it has a molar mass of 30
What is the molecular formula for ethane if it has a molar mass of 30.0 g/mol?
CH3= g/mol
Molecular formula =

42. Determine the Molecular Formula of Cadinene if it has a molar mass of 204 g and an empirical formula of C5H8

43. Ask a chemist, they always have
Ask a chemist, they always have
Solutions

44. Solutes and Solvents Solution: Solute: Solvent:
Solution:
Solute:
Solvent:
(usually found in the largest amounts)
If the solvent is water, then it is called an

45. Solubility Why does sugar “disappear” in your iced tea?
Why does sugar “disappear” in your iced tea?
How do fish breathe underwater?
Why does soda go flat faster when left out than when it is refrigerated?
It is all based on solubility!

46. Solubility
Example: iced tea
Solute
Solvent

47. States and Solutions Solutions can be any state of matter Solid-solid:
Solutions can be any state of matter
Solid-solid:
Solid-liquid:
Liquid-liquid:
Liquid-gas:
Gas-gas:

48. How Things Dissolve
Need to find/ create “__________” in water for the dissolving substance to move
Get _______________ between water molecules and molecules of the solute

49. Why some coffee is so strong it can “Put hair on your chest.”
“Strong’ coffee has more coffee dissolved in a given amount (say 1 pot) than “weak” coffee.
Strong coffee = concentrated
Weak coffee = dilute
Concentration:

50. Molarity (M) M = moles of solute
Most common way to express concentration
Molarity is the number of ____________ of solute dissolved in each __________of solution
Formula
M = moles of solute
liters of solution
Dependent on _______________
The higher the molarity the stronger the concentration

51. Practice Problems
1. What is the molarity when 6.0 moles of glucose is dissolved in water to make 3.0 L of solution.
2. How many moles of sodium chloride are there in 500 mL of 4.0 M solution?
3. What is the volume of 3.0 M solution that contains 15 moles of glucose?

52. How does something so strong become so weak?
The answer is dilution.
The more dilute something is, the lower the concentration (it’s weaker).
To accomplish this, add more solvent
How do we know how much to add?
M 1V1 = M 2V2
Typically start with a highly concentrated solution and dilute down to what you need

53. Figure 15. 8: Process of making 500 mL of a 1
Figure 15.8: Process of making 500 mL of a 1.00 M acetic acid solution.

54. End of Chapter