1. Stoichiometry

2. Molar mass of Compounds
The molar mass (MM) of a compound is determined the same way, except you add up all the atomic masses for the molecule (or compound)
Example: Molar mass of CaCl2
Aver. Atomic mass of Calcium = g/mol
Avg. atomic mass of Chlorine = g/mol
Molar mass of calcium chloride =
40.08 g/mol Ca + (2 x g/mol Cl)
 g/mol CaCl2

3. Review Practice Calculate the molar mass of calcium phosphate
= Ca3(PO4)2

4. Calculation of Stoichiometry
Converting moles A to moles of B
Converting moles A to mass B
Converting mass A to moles B
Converting mass A to mass B

5. Chocolate Chip Cookies!!!!
1 cup of butter
½ cup of white sugar
1 cup of packed brown sugar
1 teaspoon vanilla
2 eggs
2 ½ cup flour
1 teaspoon baking soda
1 teaspoon salt
2 cups semisweet chocolate chips
Makes 3 dozen cookies
How many eggs are needed to make 3 dozen cookies?
How much butter is needed for the amount of chocolate chips used?
How many eggs would we need to make 9 dozen cookies?
How much brown sugar would I need if I had 1 ½ cups of white sugar?

6. Cookies and Chemistry . . . HUH!?!?
Just like chocolate chip cookies have recipes, chemist have recipes as well
Instead of calling them recipes, we call them reaction equations
Furthermore, instead of using cups and teaspoons, we use moles
Lastly, instead of eggs, butter, sugar, etc. , we use chemical compounds as ingredients

7. Chemistry Recipes
Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe)
Be sure you have a balanced reaction before you start!!!
Example: 2 Na + Cl2  2NaCl
This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine, we will bet 2 moles of sodium chloride
What if we wanted 4 moles of NaCl? 10 moles? 50 moles?

8. Practice
Write the balanced reaction for hydrogen gas reacting with oxygen gas.
How many moles of reactants are needed?
What if we wanted 4 moles of the product?
What if we had 3 moles of oxygen, how much hydrogen would we need to react and how much product would we get?
What if we had 50 moles of hydrogen, how much oxygen would we need and how much product would we produce?

9. Mole Ratios
These mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical
Example: How many moles of chlorine is needed to react with 5 moles of sodium (without any left over)?
Balanced reaction
Calculations

10. Examples

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15. Examples

16. Converting Moles to Mass
We will use the same method as before but not stop at moles of a substance.
We will use the molar mass of the substance to find the answer.
Example: How many grams of water are made from 2 moles of hydrogen gas

17. More Examples
How many grams of hydrogen are needed if we use 3.5 mole of oxygen gas?

18. More Examples

19. More Examples

20. Converting Mass  Moles
This time we start with the mass of a substance
convert into moles using molar mass
Last just mole : mole conversion
Example: How many moles of hydrogen gas are needed when you use 5.0 g of oxygen to make water?

21. Another example
How many moles of NO are formed if 824 g of NH3 react?

22. example
How many moles of mercury (II) oxide are needed to produce 125 g of oxygen?

23. example
If 101 grams of copper are used, how many moles of copper (II) oxide will be formed?

24. Another example
If 78.2 grams of oxygen react with copper, how many moles of copper (II) oxide will be produced?

25. Mass – Mass Conversions
Most often we are given a starting mass and want to find out the mass of a product we will get (this is called the theoretical yield) or how much of another reactant we need to completely react with it (no leftover ingredients)
Now we must go from grams  moles, mole ratio, and back to grams of compound we are interested in

26. Skeleton equation:

27. Mass to Mass Conversion
Ex. Calculate how many grams of ammonia are produced when you react 2.00 g of nitrogen with excess hydrogen.
N2 + 3H2  2NH3

28. Practice
How many grams of calcium nitride are produced when 2.00 g of calcium react with excess nitrogen?

29. Chocolate Chip Cookies!!!!
1 cup of butter
½ cup of white sugar
1 cup of packed brown sugar
1 teaspoon vanilla
2 eggs
2 ½ cup flour
1 teaspoon baking soda
1 teaspoon salt
2 cups semisweet chocolate chips
Makes 3 dozen cookies

30. Limiting Reactants
Most of the time in chemistry we have more of one reactant than we need to completely use up the other reactant.
That reactant is said to be in excess (there is too much)
The other reactant limits how much product get. Once it runs out, the reaction s. This is called the limiting reactant.

31. Limiting Reactants Key  only pick one product!!!
To find the correct answer,
2 stoichiometry problems
Each problem is from one reactant to product (same product)
Lower amount of product = answer
Key  only pick one product!!!

32. Example
10.0 mols of aluminum reacts with 35.0 mols of chlorine gas to produce aluminum chloride. Which reactant is limiting, which is in excess, and how much product is produced?

33. More examples

34. Percent Yield What is it?
So far what we have calculated is the theoretical yield (paper calculations)
Most times in lab, the amount of product obtained is much less that the theoretical yield (perfect conditions do not exist in lab!!!)

35. Percent Yield What is produced in lab?
This is called the actual yield - what we really get!

36. Percent Yield
Percent yield - the ratio of the actual yield to the theoretical yield multiplied by 100.
% yield = actual yield X theoretical yield

37. Example Problem
Methanol can be produced through the reaction of CO and H2 in the presence of a catalyst.
CO(g) H2(g)  CH3OH (l)
If 75.0 g of CO reacts to produce 68.4 g of CH3OH, what is the percent yield?

38. More examples