1. Chemical Quantities and The Mole
Chapter 11
Chemical Quantities and
The Mole

2. Counting and Weighing
If one penny has a mass of 1.2 grams, how much would 5 pennies weigh?
What mass would a million pennies have?

3. How Many Pennies?
How would you be able to determine how many pennies are in the jar?
What if I told you that each penny weighs approximately 1.2 grams and that the bottle without the pennies weighs 127 g and with the pennies weighs 1.52 kg
How many pennies are in the bottle?

4. Counting and Weighing The mass of the pennies and jar is
1.52 kg x = 1520 g
Pennies in jar minus the mass of the jar = mass of pennies
1520 g g = g
1393 g x = 1161 pennies
1000 g
1 kg
1 penny
1.2 g

5. Avogadro And The Mole
The mole is just a conversion factor that allows us to accurately work with atoms and molecules.
One mole of any substance contains x 1023 units of that substance.

6. How You Measure How Much?
You can measure mass,
or volume,
or you can count pieces.
We measure mass in grams.
We measure volume in liters.
We count pieces in MOLES.

7. Moles
Defined as the number of carbon atoms in exactly 12 grams of carbon-12.
1 mole is 6.02 x particles.
Treat it like a very large dozen
6.02 x is called Avogadro’s number.

8. Representative Particles
The smallest pieces of a substance.
For a molecular compound it is a molecule.
For an ionic compound it is a formula unit.
For an element it is an atom.

9. Types of Questions How many oxygen atoms are in the following? CaCO3
Al2(SO4)3
How many ions are in the following?
CaCl2
NaOH

10. Types of Questions
How many molecules of CO2 are there in 4.56 moles of CO2 ?
How many moles of water is 5.87 x molecules?
How many atoms of carbon are there in 1.23 moles of C6H12O6 ?
How many moles is 7.78 x 1024 formula units of MgCl2?

11. Measuring Moles Remember average atomic mass?
The amu was one-twelfth the mass of a carbon 12 atom.
Since the mole is the number of atoms in 12 grams of carbon-12,
the atomic mass on the periodic table is also the mass of 1 mole of those atoms in grams.

12. Molar Mass The mass of 1 mole of an element in grams.
12.01 grams of carbon has the same number of pieces as grams of hydrogen and grams of iron.
We can write this as g C = 1 mole
We can count things by weighing them.

13. Examples How much would 2.34 moles of carbon weigh?
How many moles of magnesium are in g of Mg?
How many atoms of lithium are in 1.00 g of Li?
How much would 3.45 x 1022 atoms of U weigh?

14. What About Compounds?
in 1 mole of H2O molecules there are two moles of H atoms and 1 mole of O atoms
To find the mass of one mole of a compound
determine the moles of the individual elements contained
Determine how much each element would weigh
add them up

15. What About Compounds? What is the mass of one mole of CH4?
1 mole of C = g
4 mole of H x 1.01 g = 4.04g
1 mole CH4 = = 16.05g
The Molar Mass of CH4 is 16.05g
The mass of one mole of a molecular compound.

16. Molar Mass Ionic Compound
How do you find the mass of one mole of an ionic compound?
Calculated the same way as molecular compound before
What is the Molar Mass of Fe2O3?
2 moles of Fe x g = g
3 moles of O x g = g
Molar Mass = g g = 159.7g

17. Molar Mass The generic term for the mass of one mole.
The same as gram molecular mass, gram formula mass, and gram atomic mass.

18. Examples
Calculate the molar mass of the following and tell me what type it is.
Na2S
N2O4 C
Ca(NO3)2
C6H12O6
(NH4)3PO4

19. Finding Moles of Compounds Counting Pieces by Weighing
Using Molar Mass
Finding Moles of Compounds
Counting Pieces by Weighing

20. Using Molar Mass
We can find the mass ‘grams’ of 1 mole of atoms, ions, or molecules.
We can make conversion factors from these.
To change grams of a compound to moles of a compound.

21. For Example
How many moles is 5.69 g of NaOH?

22. For Example
How many moles is 5.69 g of NaOH?

23. For Example How many moles is 5.69 g of NaOH?
need to change grams to moles

24. For Example How many moles is 5.69 g of NaOH?
need to change grams to moles
for NaOH

25. For Example How many moles is 5.69 g of NaOH?
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g

26. For Example How many moles is 5.69 g of NaOH?
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g
1 mole NaOH = g

27. For Example How many moles is 5.69 g of NaOH?
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g
1 mole NaOH = g

28. For Example How many moles is 5.69 g of NaOH?
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g
1 mole NaOH = g

29. Examples How many moles is 4.56 g of CO2 ?
How many grams is 9.87 moles of H2O?
How many molecules in 6.8 g of CH4?
49 molecules of C6H12O6 weighs how much?

30. Percent Composition Like all percents Part x 100 % Whole
Find the mass of each component,
Divide by the total mass.
Movie

31. Example
Calculate the percent composition of a compound that is 29.0 g of Ag with 4.30 g of S.

32. Getting It From The Formula
If we know the formula, assume you have 1 mole.
Then you know the pieces and the whole.

33. Examples Calculate the percent composition of C2H4?
Aluminum carbonate.

34. From Percentage to Formula
Empirical Formula
From Percentage to Formula

35. The Empirical Formula
The lowest whole number ratio of elements in a compound.
The molecular formula is the actual ratio of elements in a compound.
The two can be the same.
CH2 empirical formula
C2H4 molecular formula
C3H6 molecular formula
H2O both

36. Calculating Empirical
Just find the lowest whole number ratio
C6H12O6
CH4N
It is not just the ratio of atoms, it is also the ratio of moles of atoms.
In 1 mole of CO2 there is 1 mole of carbon and 2 moles of oxygen.
In one molecule of CO2 there is 1 atom of C and 2 atoms of O.

37. Calculating Empirical
Means we can get ratio from percent composition.
Assume you have a 100 g.
The percentages become grams.
Can turn grams to moles.
Find lowest whole number ratio by dividing by the smallest.

38. Example
Calculate the empirical formula of a compound composed of % C, % H, and %N.
Assume 100 g so…
38.67 g C x 1mole C = mole C g C
16.22 g H x 1mole H = mole H g H
45.11 g N x 1mole N = mole N g N

39. Example The ratio is 3.220 mole C = 1 mole C 3.220 mole N 1 mole N
The ratio is mole H = 5 mole H mole N mole N
C1H5N1
A compound is % P and % O. What is the empirical formula?
Caffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% O. What is its empirical formula?

40. Empirical to Molecular
Since the empirical formula is the lowest ratio the actual molecule would weigh more.
By a whole number multiple.
Divide the actual molar mass by the mass of one mole of the empirical formula.
Caffeine has a molar mass of 194 g. what is its molecular formula?

41. Example
A compound is known to be composed of % Cl, 24.27% C and 4.07% H. Its molar mass is known (from gas density) to be g. What is its molecular formula?

43. Gases and the Mole

44. Gases Many of the chemicals we deal with are gases.
They are difficult to weigh.
Need to know how many moles of gas we have.
Two things effect the volume of a gas
Temperature and pressure
Compare at the same temp. and pressure.

45. Standard Temperature and Pressure
0ºC and 1 atm pressure
abbreviated STP
At STP 1 mole of gas occupies 22.4 L
Called the molar volume
Avagadro’s Hypothesis - at the same temperature and pressure equal volumes of gas have the same number of particles.

46. Examples What is the volume of 4.59 mole of CO2 gas at STP?
How many moles is L of O2 at STP?
What is the volume of 8.8g of CH4 gas at STP?

47. Density of a Gas D = m /V for a gas the units will be g / L
We can determine the density of any gas at STP if we know its formula.
To find the density we need the mass and the volume.
If you assume you have 1 mole than the mass is the molar mass (MM).
At STP the volume is 22.4 L.

48. Examples Find the density of CO2 at STP.
Find the density of CH4 at STP.

49. The Other Way
Given the density, we can find the molar mass of the gas.
Again, pretend you have a mole at STP, so V = 22.4 L.
m = D x V
m is the mass of 1 mole, since you have 22.4 L of the stuff.
What is the molar mass of a gas with a density of g/L?
2.86 g/L?

50. All The Things We Can Change

51. We Have Learned How To change moles to grams moles to atoms
moles to formula units
moles to molecules
moles to liters of gas
molecules to atoms
formula units to atoms
formula units to ions

52. Mass
Moles

53. Mass MM
Moles

54. Mass
Volume MM
Moles

55. Mass
Volume
22.4 L MM
Moles

56. Mass
Volume
22.4 L MM
Moles
Representative
Particles

57. Mass
Volume
22.4 L MM
Moles
6.02 x 1023
Representative
Particles

58. Mass
Volume
22.4 L MM
Moles
6.02 x 1023
Representative
Particles
Atoms

59. Mass Volume Moles 6.02 x 1023 Representative Particles Ions AtomsMM
Moles
6.02 x 1023
Representative
Particles
Ions
Atoms