1. The Mole and Stoichiometry
SC3. Obtain, evaluate, and communicate information about how the Law of Conservation of Matter is used to determine chemical composition in compounds and chemical reactions.
c. Use mathematics and computational thinking to apply concepts of the mole and Avogadro’s number to conceptualize and calculate • percent composition • empirical/molecular formulas • mass, moles, and molecules relationships • molar volumes of gases
d. Use mathematics and computational thinking to identify and solve different types of reaction stoichiometry problems (i.e., mass to moles, mass to mass, moles to moles, and percent yield) using significant figures. (Clarification statement: For elements c and d emphasis is on use of mole ratios to compare quantities of reactants or products and on assessing students’ use of mathematical thinking and not on memorization and rote application of problem-solving techniques.)
e. Plan and carry out an investigation to demonstrate the conceptual principle of limiting reactants.

2. The Mole A counting unit
Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000
6.02 X 1023
This number is named in honor of Amadeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were always the same number of molecules present

3. Just How Big is a Mole?
Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles.
If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles.
If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

4. The Mole 1 dozen cookies = 12 cookies
1 mole of cookies = 6.02 X cookies
1 dozen cars = 12 cars
1 mole of cars = 6.02 X 1023 cars
1 dozen Al atoms = 12 Al atoms
1 mole of Al atoms = 6.02 X atoms
Note that the NUMBER is always the same, but the MASS is very different!

5. A Mole of Particles contains 6.02 x 1023 particles
1 mol C = x 1023 C atoms
1 mol H2O = x 1023 H2O molecules
1 mol NaCl = x 1023 NaCl formula units
6.02 x 1023 Na+ ions and
6.02 x 1023 Cl– ions

6. Composition Stoichiometry
Stoichiometry is the calculation of relative quantities of reactants and products in chemical reactions.
We will start by calculating independent quantities of the reactants and products, or what the reactions are “composed of”
Composition Stoichiometry

7. Moles to Particles Conversion
Note that a particle could be an atom, molecule or formula unit! ÷ by Avogadro’s Number Particles Moles × by Avogadro’s Number

8. Particles and Moles
Ammonia gas is used extensively industrially to produce fertilizer, plastics, and explosives. If 3.01 × 1023 molecules of NH3 are reacted, how many moles is that?

9. 1. Particles to moles means you divide by Avogadro’s number
2. Avogadro’s number = 6.02 × 1023 particles
mol
3. Setup
3.01 × 1023 molecules NH mol
6.02 × 1023 molecules
Answer = mol NH3

10. Learning Check
1. Number of atoms in mole of Al a) 500 Al atoms b) 6.02 x 1023 Al atoms c) 3.01 x 1023 Al atoms 2.Number of moles of S in 1.8 x 1024 S atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x 1048 mole S atoms

11. Molar Mass The mass, in grams, of 1 mole of a substance
Equal to the numerical value of the average atomic mass (get from periodic table)
1 mole of C atoms = g
1 mole of Mg atoms = 24.3 g
1 mole of Cu atoms = 63.5 g

12. Other Names Related to Molar Mass
Molecular Mass/Molecular Weight: If you have a single molecule, mass is measured in amu’s instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different. (24.4 amu)
Formula Mass/Formula Weight: This is used for ionic compounds. But again, the numerical value is the same. Only the units are different. (f.w. 48.8)
THE POINT: You may hear all of these terms which mean the SAME NUMBER… just different units

13. Learning Check = 79.9 g/mol 1 mole of Br atoms 1 mole of Sn atoms
Find the molar mass (usually we round to the tenths place)
= 79.9 g/mol
1 mole of Br atoms
1 mole of Sn atoms
= g/mol

14. Molar Mass of Compounds
Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = ? 1 mole Ca x 40.1 g/mol = 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 71.0 g/mol g/mol

15. Learning Check Molar Mass of K2O = ? Molar Mass of N2O4 = ?
Molar Mass of Al2(SO4)3 = ?

16. Moles to Grams Conversion
÷ by molar mass Grams Moles × by molar mass

17. Mass and Moles
Aluminum is often used for the structure of light-weight bicycle frames. What is the mass of 3.00 moles of Al?

18. 1. Moles to grams means you multiply by molar mass 2
1. Moles to grams means you multiply by molar mass 2. Molar mass of Al 27.0 g/mol 3. Setup 3.00 moles Al 27.0 g mol Answer = 81.0 g Al

19. Learning Check
The artificial sweetener aspartame (formula C14H18N2O5) is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

20. Volume and Moles
Under specific conditions, all gases, regardless of identity, contain the same number of particles in a definite volume.
Those specific conditions are called STP –
Standard Temperature and Pressure
Occurs at 273 K (0°C) and 1 atm of pressure
At STP, 22.4 L of any gas contains 1 mole of gas particles.
This is referred to as molar volume

21. Moles to Liters Conversion
THIS CAN ONLY WORK FOR GASES AT STP
÷ by molar volume
Liters Moles
× by molar volume

22. Volume and Moles
At STP, a balloon is filled with helium. If the balloon has a volume of L, how many moles of gas is inside?

23. 1. Volume to moles means you divide by molar volume 2. Molar volume 22
1. Volume to moles means you divide by molar volume 2. Molar volume 22.4 L/mol 3. Setup L He mol 22.4 L Answer = 4.70 mol He

24. Learning Check
Sulfur dioxide is a gas produced by burning coal. Determine the volume of 0.60 mol of SO2 gas.

25. grams
moles
particles
liters
THE MOLE ROADMAP

26. Learning Check!
How many atoms of Cu are present in g of Cu?

27. Learning Check!
What is volume of 1.20 x 1024 molecules of hydrogen sulfide gas?

28. How many liters of O are present in 78.1 g of oxygen gas?
Learning Check!

29. 4 NH O2 4 NO H2O
Four molecules of NH3 react with five molecules of O2 to form four molecules of NO and six molecules of H2O. OR
A reaction between four moles of NH3 and five moles of O2 yields four moles of NO and six moles of H2O.
Mole Relationships

30. 4 NH O2 4 NO H2O
Mole ratios allow you to relate ANY TWO substances in a chemical equation.
4 NH NO O2 6 H2O
5 O H2O NO 4 NH3
Mole Ratio

31. Reaction Stoichiometry
Before, we used the road map for a single substance.
Now we will use the road map AND mole ratios AND a balanced equation to calculate the amount of any substance in a reaction, given at least one known amount of a different substance.
Reaction Stoichiometry

32. The reaction mole road map now looks like this…
Mole Ratio
Between A and B
Substance A
(NOT in moles)
Substance B
(NOT in moles)
Moles of A
Moles of B

33. When N2O5 is heated, it decomposes into NO2 and O2
When N2O5 is heated, it decomposes into NO2 and O2. How many moles of N2O5 are needed to produce 75.0 g of O2?
Examples

34. Zinc metal reacts with hydrochloric acid to produce zinc chloride and hydrogen gas. If 45.5 g of zinc is used, how much zinc chloride is produced?
Examples

35. Limiting Reactant A limiting reactant in a chemical reaction is the
substance that
Is used up first.
Stops the reaction.
Limiting Reactant

36. Example of Everyday Limiting Reactant
How many peanut butter sandwiches could be made from 8 slices bread and 1 jar of peanut butter?
With 8 slices of bread, only 4 sandwiches could be made. The bread is the limiting item.

37. Example of Everyday Limiting Reactant
How many peanut butter sandwiches could be made from 8 slices bread and 1 tablespoon of peanut butter?
With 1 tablespoon of peanut butter, only 1 sandwich could be made. The peanut butter is the limiting item.

38. Example Limiting Reactant Calculation:
A 2.00 g sample of ammonia is mixed with g of oxygen.  Which is the limiting reactant and how much excess reactant remains after the reaction has stopped?
First, we need to create a balanced equation for the reaction:
4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g)

39. Calculate how many moles of each? 

40. The reactant that produces the lesser amount of product in this case is the oxygen, which is thus the "limiting reactant." Next, to find the amount of excess reactant, we must calculate how much of the non-limiting reactant (ammonia) actually did react with the limiting reactant (oxygen).

41. Limiting Reactants Example Problem 1
When 4.00 mol H2 is mixed with 2.00 mol Cl2,how
many moles of HCl can form?
H2(g) Cl(g)  2HCl (g)
4.00 mol mol ??? mol
Calculate the moles of product from each reactant, H2 and Cl2.
The limiting reactant is the one that produces the smaller amount of product.
Limiting Reactants

42. Limiting Reactants Using Moles
How much HCl can be formed from the H2?
4.00 mol H2 x 2 mol HCl = mol HCl
1 mol H2
HCl from Cl2
2.00 mol Cl2 x 2 mol HCl = mol HCl
1 mol Cl (smaller)
The limiting reactant is Cl2 because it is used up first. Thus Cl2 produces the smaller number of moles of HCl.
Limiting Reactants Using Moles

43. Limiting Reactants Using Mass
Example Problem 2
If 192 grams Ca mixed with 56 grams N2, which is the limiting reactant?
3Ca(s) + N2(g)  Ca3N2(s)

44. Example Problem 3 Calculate the mass of water produced when 8
Example Problem 3 Calculate the mass of water produced when 8.00 g H2 and 24.0 g O2 react. Which is the limiting reactant?

45. Limiting Reactants Using Mass
Example Problem 4
What is the limiting reactant when Silver metal reacts with sulfur to form silver sulfide. If you have 50 grams of Silver and 10 g of Sulfur
Limiting Reactants Using Mass