1. Stoichiometry & the Mole

2. Dimensional Analysis Review
How many seconds are in 5.0 hours?
5.0 hr
5.0 hr x 60 min x 60 sec = sec
1 hr min

3. Stoichiometry
Stoichiometry is just a long word for changing units in chemistry
If you can do Dimensional Analysis, you can do stoichiometry

4. The Mole
Chemists need a convenient method for counting accurately the number of atoms, molecules, or formula units in a sample of a substance.
The mole, commonly abbreviated mol, is the SI base unit used to measure the amount of a substance.

5. The Mole
A mole of anything contains x 1023 representative particles.
A representative particle is any kind of particle such as atoms, molecules, formula units, electrons, or ions.
In this class, Avogadro’s number will be rounded to three significant figures— 6.02 x 1023.

6. Conversion Factor #1

7. Mole – Representative Particle Calculations
Calculate the number of atoms in 3.50 moles of copper
Start with your given
3.50 mol Cu
Draw your line
3.50 mol Cu x _________

8. Mole – Representative Particle Calculations
Place the conversion factors
3.50 mol Cu x 6.02 x 1023 atoms
1 mol Cu
Work the problem
2.11 x atoms Cu

9. Mole – Representative Particle Calculations
How many moles of MgO are in 9.72 x molecules of MgO?
1.61 mol MgO

10. Mole – Mass Relationship
The mass in grams of one mole of any pure substance is called its molar mass.
The molar mass of any element is numerically equal to its atomic mass and has the units g/mol.

11. Conversion Factor # 2 1 mole Molecular weight (g)
The molecular mass comes from the periodic table!

12. Calculating Molecular Mass
What is the molecular mass of (C3H5)2S?
C = 6 (12.01) = 72.06
H = 10 (1.01) = 10.10
S = 1 (32.07) = 32.07
Total = g/mol

13. Mole – Mass Calculations
What is the mass of 4.21 moles of iron (III) oxide?
Start with your given:
4.21 mol Fe2O3
Draw your line
4.21 mol Fe2O3 x _____________

14. Mole – Mass Calculations
Place conversion factors
4.21 mol Fe2O3 x g Fe2O3
1 mol Fe2O3
Cross out units & work the problem
672 g Fe2O3

15. Mole – Mass Calculations
How many moles of Ca(OH)2 are in 325 grams?
4.39 moles Ca(OH)2

16. Mass – Particle Conversions
How many atoms of gold are in 25.0 g of gold?
25.0 g Au x 1 mol Au x 6.02 x 1023 atoms Au
g Au mol Au
7.65 x 1022 atoms of Au

17. Stoichiometry
Using the methods of stoichiometry, we can measure the amounts of substances involved in chemical reactions and relate them to one another.

18. The #’s in from if A & B MUST come from the balanced chemical equation
Conversion Factor # 3
# Moles A
# Moles B
The #’s in from if A & B MUST come from the balanced chemical equation

19. Mole – Mole Relationship
4 Fe + 3O2  2Fe2O3
4 mol Fe / 3 mol O2
4 mol Fe / 2 mol Fe2O3
3mol O2 / 2 mol Fe2O3

20. Mole – Mole Relationship
How many moles of Fe2O3 will I form from 5.0 mol of Fe?
5.0 mole Fe x 2 mol Fe2O3
4 mol Fe
2.5 mol Fe2O3

21. Mass – Mole Relationship
How many g of NaCl will be produced from 1.25 mol of chlorine gas reacting with sodium?
Write the reaction
Na + Cl2  NaCl
Balance the reaction
2Na + Cl2  2NaCl

22. Mass – Mole Relationship
Work the problem
1.25 mol Cl2 x 2 mol NaCl x g NaCl
1 mol Cl mol NaCl
146 g NaCl

23. Mass – Mass Relationships
Ammonium nitrate decomposes into dinitrogen monoxide gas and water. Determine that amount of water produced if 25.0 g of ammonium nitrate decomposes.
NH4NO3  N2O + H2O
NH4NO3  N2O + 2 H2O

24. Mass – Mass Relationships
25.0 g NH4NO3 x 1 mol NH4NO3 x 2 mol H2O x g H2O
80.04 g NH4NO mol NH4NO mol H2O
11.2 g H2O

25. Steps Write the chemical equation Balance the chemical equation
Start with your given
Cross out until you get what you want
Check significant digits, units, and circle your answer

26. Conversion Factors 1 mol 6.02 x 10 23 particles mw in grams # mol A
# mol B