1. Chemical Quantities

2. 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.

3. Moles
A unit of measure
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 Avagadro’s number.

4. 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 (simplest ratio).
For an element it is an atom.

5. Measuring Moles
Since the mole is the number of atoms in 12 grams of carbon-12,
the decimal number on the periodic table is also the mass of 1 mole of those atoms in grams (this goes for all elements).

6. 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 right this as g C = 1 mole
We can count things by weighing them.

7. 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 elements they have
Find out how much they would weigh
add them up

8. 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.

9. Molar Mass The mass of one mole of an ionic compound.
Calculated the same way.
What is the molar mass of Fe2O3?
2 moles of Fe x g = g
3 moles of O x g = g
The molar mass = g g = g

10. YOU TRY #1 Calculate the molar mass of the following A. Na2S B. N2O4
C. C
D. Ca(NO3 )2
E. C6H12O6
F. (NH4 )3PO4

11. Using Molar Mass Both Mass 6.02 x 1023 PT Moles Representative
Particles
Moles
6.02 x 1023 PT
Both

12. Molar Mass The number of 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.

13. For example
How many moles is 5.69 g of NaOH?

14. For example
How many moles is 5.69 g of NaOH?

15. For example How many moles is 5.69 g of NaOH?
need to change grams to moles

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

17. 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

18. 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

19. 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

20. 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

21. More Examples How much would 2.34 moles of carbon weigh?
How many atoms of lithium in 1.00 g of Li?
How many molecules in 6.8 g of CH4?
How many grams is 9.87 moles of H2O?

22. YOU TRY #2 A. How many moles of magnesium in 24.31 g of Mg?
B. How much would 3.45 x 1022 atoms of U weigh?
C. How many moles is 4.56 g of CO2 ?
D. 49 molecules of C6H12O6 weighs how much?

23. All the things we can change

24. Mass
Moles

25. Mass PT
Moles

26. Mass PT
Moles
Representative
Particles

27. Mass PT
Moles
6.02 x 1023
Representative
Particles

28. Mass PT
Moles
6.02 x 1023
Representative
Particles
Atoms

29. Mass Moles 6.02 x 1023 Representative Particles Ions Atoms MoleculesPT
Moles
6.02 x 1023
Representative
Particles
Ions
Atoms
Molecules

30. Percent Composition Like all percents Part x 100 % = % whole
Find the mass of each component,
divide by the total mass.
Molar mass of element (g) x 100 = % of element
Molar mass of formula (g)

31. Example Calculate the percent composition of Cu2S?
Cu = g x 2 = g
S = g --- Cu2S = g
% Cu
127.10g
159.16g
TIP - Each % should add up to equal
100%!!!!!!!!!!!!
x 100 = % Cu
% S
32.06 g
159.16g
x 100 = % S

32. Calculate the percent composition of glucose C6H12O6
Example 2
Calculate the percent composition of glucose C6H12O6
Molar mass breakdown
C = g
H = g
O = g
Total = g
% C = 72.06g g
x 100 = %
% H = 12.12g
180.18g
x 100 = 6.73 %
% O = 96 g
180.18g
x 100 = %

33. You Try #3 Potassium nitrate H2SO4 C2H5OH C6H5NH2
Find the percent composition of the following
Potassium nitrate
H2SO4
C2H5OH
C6H5NH2

34. Percent composition with WATER
Some compounds trap water molecules
Sodium carbonate – it traps 10 water molecules for every 1 sodium carbonate
Na2CO H2O
To calculate the percent of water…
1. Find the molar mass of the WHOLE formula
Sometimes this number is given
2. Find the molar mass of the water present
3. Mm of water (g) x 100% = % water
mm of whole formula (g)

35. Example 1
Calculate the percent of water in Na2CO H2O. It has a molar mass of g.
Molar mass of water
breakdown
H = 1.01g x 20 = g
O = 16.00g x 10 = g
Total mm of water=180.20g
% H2O = g
286.14g
x 100 = % H2O

36. Calculate the percent composition of water in ZnSO4 7H2O
Example 2
Calculate the percent composition of water in ZnSO4 7H2O
Molar mass breakdown
Zn = g
S = g
O = 16.00g x 4 = 64.00g
H = 1.01g x 14 = g
O = 16.00g x 7 = g
Molar mass
Of WHOLE
Formula = g
Molar mass
Of water only = g
% H2O = g g
x 100 = %

37. You Try #4 Calculate the percent composition of water in CuSO4 5H2O
B. Find the percentage of water in MgSO4 7H2O

38. From percentage to formula
Empirical Formula
From percentage to formula

40. The Empirical Formula
The lowest whole number ratio of elements in a compound (reduced form).
The molecular formula 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
Just find the lowest whole number ratio

41. 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.
Remember conversions!!!!!!!!
Find lowest whole number ratio by dividing by the smallest mole number.

42. Example 1
NOW divide by your smallest mole number to get a whole number ratio…
Calculate the empirical formula of a compound composed of % C, % H, and %N.
Assume 100 g so
38.67 g C x 1mol C = 3.22 mole C g C
16.22 g H x 1mol H = mole H g H
45.11 g N x 1mol N = 3.22 mole N g N
3.22/3.22 = 1 mole C
16.06/3.22 = 5 moles H
3.22/3.22 = 1 mole N
Empirical formula = CH5N
This is the ONLY time you can round !!!

43. Example 2
NOW divide by your smallest mole number to get a whole number ratio…
Calculate the empirical formula of a compound composed of 70 % Mn and 30% O.
Assume 100 g so
70 g Mn x 1mol Mn = 1.27 mol Mn g Mn
30 g O x 1mol O = mole O g O
1.27/1.27 = 1 mole Mn
1.88/1.27 = 1.5 moles O
BUT only
round to the
nearest whole
or half number
Empirical formula = Mn2O3
This is the ONLY time you can round !!!

44. You Try #5 Determine the formula for a black,
powdery compound made of 63%
manganese and 37% oxygen.
Find the formula for an ingredient of
rechargeable batteries that has the following
percentage composition: 21.9% O, 1.4% H,
and 76.7% Cd.

45. Brew Tech Camp Stew Sale 84 potatoes 63 carrots 15 onions
3 heads of garlic
27 turnips
42 pieces of celery
9 cans of green beans
6 cans of tomatoes
6 cans of corn
6 cans of lima beans
12 lbs. of beef
6 bottles of hot sauce
6 gallons of water

46. Empirical to molecular
Related by a whole number multiple.
Divide the actual molar mass by the the mass of one mole of the empirical formula.

49. Example (easy type)
Determine the molecular formula of a compound having an empirical formula of CH and a molar mass of g.
GIVEN:
empirical = CH
mm = g
First step:
calculate the molar mass of the empirical…
13.02 g
Next step:
find the multiple
78.11
13.02
= 6
Final step:
run the multiple through the empirical to get your molecular
C6H6

50. Example 2 (a bit more challenging)
A compound has the following composition: 76.54% C, 12.13% H, 11.33% O. If its molar mass is g, what is its molecular formula?
GIVEN:
mm = g
% per element
NOW divide by your smallest mole number to get a whole number ratio…
First step:
calculate the empirical…
76.54 g C x 1mol C = 6.37 mol C g C
12.13 g H x 1mol H = mol H
1.01 g H
11.33 g O x 1mol O = mole O g O
6.37/0.71 = moles C
12.01/0.71 = 17 moles H
0.71/0.71 = mole O
Empirical formula = C9H17O

51. Example 2 CONTINUED
A compound has the following composition: 76.54% C, 12.13% H, 11.33% O. If its molar mass is g, what is its molecular formula?
First step:
calculate the molar mass of the empirical (C9H17O)… g
Next step:
find the multiple
282.45
141.26
= 2
Final step:
run the multiple through the empirical to get your molecular
C18H34O2

52. You Try #6
A. The empirical formula for mercury (I) chloride is found to be HgCl. The molar mass is found to be g. Molecular formula is…
The empirical formula for trichloroisocyanuric acid, the active ingredient in dry household bleach, is OCNCl (that last letter is an L). The molar mass is g. What is the molecular formula?
Calculate the molecular formula for a compound that has a molar mass of g and contains 83.62% carbon and 16.38% hydrogen.