1. Unit 9 mathematics of chemistry

2. AIM # 1 : How can we calculate gram formula mass?
The atomic mass of an element is found in each element box on the Periodic Table
The number of atoms of each element present in a compound is denoted by the subscripts on each element

3. Gram formula mass is the mass of the smallest unit of a compound from the sum of the atomic masses of all atoms present

4. GFM of K2CO3 Add them all up to get gfm Element # of atoms X Mass
Multiplied result
Add them all up to get gfm

5. Calculate the gram formula mass of the following:
1. N2H2
2. H2SO4
3. CuSO4 H20

6. AIM# 2 : What is meant by the percent composition of a compound?
Percent Composition represents the composition as a percentage of each element compared with the total mass of the compound

7. % composition =
mass of part
mass of whole
x 100  TABLE ____

8. Practice What is the percentage, by mass, of O in Fe2O3? Element
# atoms X Mass #
Multiplied result
Add them all up to get gfm Fe O

9. Practice 2. What is the percentage, by mass, of O in CO2? Element
# atoms X Mass #
Multiplied result
Add them all up to get gfm l

10. Hydrates: crystals that contain attached water molecules
To calculate the percentage of water in a hydrate, treat the water molecule as a single unit

11. What is the percentage, by mass, of water in sodium carbonate crystals, Na2CO3 10H2O?

12. AIM# 3: What is a mole? Mole is a way to express a quantity
1 mole of any compound or elements = mass of that compound or element
1 mole = 6.02 x 1023 particles (atoms or molecules)
1 mole = 22.4 L
Formula is on Table T

13. What is a mole?
MOLE TRIANGLES

14. PRACTICE 1. How many moles are equivalent to 4.75 g of NaOH?
Element
# atoms X Mass #
Multiplied result
Add them all up to get gfm

15. PRACTICE 2. How many grams are equivalent to 2.8 moles of NaOH?
Element
# atoms X Mass #
Multiplied result
Add them all up to get gfm

16. Aim # 4 How can we use mole relationships to solve stoichiometry problems?
Like following a recipe
Need a balanced chemical equation
Use mole relationships
The study of quantities of materials consumed and produced in chemical reactions

17. Practice …..like following a recipe
Directions: Use the pancake recipe below in order to answer the following questions
How much of the following starting materials do we need in order to make 14 pancakes?
How many cups of pancakes mix would we need to use in order to make 28 pancakes?
How many cups of pancake mix would we need to use in order to make 7 pancakes?
1 cup of milk + ____________________________ = 14 pancakes
Are the units used for all 4 substances in the equation the same?

18. Formula:

19. If we had 5 moles of H2, how many moles of O2 are required?

20. If we have 23 grams of Na how many moles of H2 are produced?

21. If we have 2 moles of N2 how many grams of H2 are needed?

22. AIM# 5: How can we calculate empirical and molecular formulas?
convert % to grams
divide each element by mass #
Divide each quotient by smallest value calculated Round your results to nearest whole number
Use whole #s to write empirical formula
Sequence of elements in the question is the same as in the formula

23. A compound is composed of 50% Sulfur, 50% Oxygen; determine the empirical formula

24. determine the gfm of the empirical formula
MOLECULAR
determine the gfm of the empirical formula
Divide the given molecular mass by the gfm
Might have to calculate empirical formula
Given molecular mass
Multiply your whole number result by the empirical formula to determine molecular formula

25. Upon analysis the empirical formula is determined to be CH2O
Upon analysis the empirical formula is determined to be CH2O. The mass of the compound is 180amu. Determine the molecular formula