1. 1
Stoichiometry is the part of chemistry that studies amounts of substances that are involved in reactions.
Stoichiometry
STOY-KEE-AHM-EH-TREE

2. 1. Demonstrate the conceptual principle of limiting reactants.2
GOALS
1. Demonstrate the conceptual principle of limiting reactants.
2. Explain the role of equilibrium in chemical reactions
3. Identify and solve different types of stoichiometry problems, specifically relating mass to moles and mass to mass.
The Mole Song- A Review

3. Moles & Molar Mass Review3
Before we start…let’s review…..
Moles & Molar Mass Review
1 mole is _______ atoms/molecules
How many atoms are in 1.5 moles of neon?
Calculate the number of grams in 3.25-mol of AgNO3
How many moles are there in grams of sodium phosphate (Na3PO4)?
How many grams are in 5.6 x 1023 atoms of Zinc?

4. Practice with a Friend 4
Practice with a Friend 
What is the mass of 7.50 moles of sulfur dioxide (SO2)?
How many moles are there in 21.4 grams of nitrogen gas (N2)?
How many moles are there in grams of sodium phosphate (Na3PO4)?
How many calcium atoms would be in a 100 gram sample of calcium metal?
Find the mass in grams of 7.5  1015 atoms of nickel.

5. “amounts of substances that are involved in reactions”5
Stoichiometry
“amounts of substances that are involved in reactions”
Stoichiometry
is the calculation of relative quantities of reactants and products in chemical reactions
helps you figure out how much of a compound you will need, or maybe how much you started with.
2HCl + Ba(OH)2  2H2O + BaCl2 1 1
coefficients give MOLAR RATIOS
What are some molar ratio we
can write from this equation?

6. “amounts of substances that are involved in reactions”6
Stoichiometry
“amounts of substances that are involved in reactions”
What do we know from this equation?
there is: one mole of CH4 for every two moles of H2O
there is: one mole of CH4 for every one mole of CO2
there are: 2 molecules of O2 for every one molecule of CO2
there are even: four atoms of H in CH4 for every two atoms of O in 2H2O

7. How can we write these as conversion factors?7
Stoichiometry
CH4 + 2O2  CO2 + 2H2O
there is: one mole of CH4 for every two moles of H2O
there are: 2 molecules of O2 for every one molecule of CO2
there are even: four atoms of H in CH4 for every two atoms of O in 2H2O
How can we write these as conversion factors?

8. Now you try: Write as many conversion factors as you can8
Stoichiometry
Now you try: Write as many conversion factors as you can
1) C3H8 + 5O2  3CO2 + 4H2O
What do we know from the balanced equation?
• 1 molecule of propane for every 3 molecules of CO2
• 3 atoms of C in propane for 4 molecules of water
• 9 atoms of hydrogen in propane for 8 atoms of hydrogen in water
2) Fe + S  FeS
       What do we know from the balanced equation?
         
1 atom  of Fe   +   1 atom  of S  ---->   1 molecule of FeS                
10 atoms of Fe  + 10 atoms of S ----> 10 molecules of FeS
55.8 mg of Fe  +      32.1 mg S  ---->   87.9 mg  FeS
5.58 g of Fe     +      3.21 g of S ----> 8.79 g of FeS

9. 2 CH3OH (l) + 3 O2 (g) --> 2 CO2 (g) + 4 H2O (l)
Our goal.. To be able to determine amounts of products and reactants…moles and grams….for ANY chemical reaction.
2 CH3OH (l) + 3 O2 (g) --> 2 CO2 (g) + 4 H2O (l)
Cutesy….but GOOD… video clip about mole conversions.
After this video, we will now have a class rule about all conversions….
You must go through………

10. Mole to Mole 2KClO3 → 2KCl + 3O2
In the lab, you can’t work with single atoms or molecules. So, it is useful to be able to identify how many moles of one substance you need to make a certain amount of another substance.
Mole to Mole 9
2KClO3 → 2KCl + 3O2
How many moles of oxygen are produced by the decomposition of 6.0 moles of potassium chlorate?
N2 + 3H2 → 2NH3
How many moles of hydrogen are needed to completely react with 2.0 moles of nitrogen?

11. Mole to Mole Practice 5C(s) + 2SO2(g) ----> CS2(s) + 4CO(g)10
Carbon disulfide is an important industrial solvent. It is prepared by the reaction of carbon with sulfur dioxide:
5C(s) + 2SO2(g) ----> CS2(s) + 4CO(g)
How many moles of CS2 form when 6.3 mol of C reacts?
How many moles of carbon are needed to react with 7.24 moles of SO2?

12. Mole to Mole Practice 2AgNO3+ Ca Ca(NO3)2 + 2Ag11
Silver can be made according to the following equation:
2AgNO3+ Ca Ca(NO3) Ag
-If 35.3 moles of silver nitrate are reacted how many moles of silver are produced?

13. Mole to Mole Practice with a Friend12
Mole to Mole Practice with a Friend
Use the following equation to answer the questions below:
2 CH3OH (l) + 3 O2 (g) --> 2 CO2 (g) + 4 H2O (l)
How many moles of water will be produced from the combustion of 0.27 moles of CH3OH?
How many moles of O2 are needed to burn 2.56 moles of CH3OH?
How many moles of CO2 are produced from the combustion of 5.25 moles of CH3OH?
How many moles of water are produced when 3.25 moles of CO2 are formed?
0.54 mol H2O
3.84 mol O2
5.25 mol CO2
6.50 mol H2O

14. Mole to Mole Practice with a Friend13
When N2O5 is heated, it decomposes:
2N2O5(g)  4NO2(g) + O2(g)
5. How many moles of NO2 can be produced from 4.3 moles of N2O5?
4.3 mol N2O5
8.6
= moles NO2
6.How many moles of O2 can be produced from 4.3 moles of N2O5?
4.3 mol N2O5
= moles O2
2.2

15. Mass to Moles/ Moles to Mass14
2 KClO3 ---> 2 KCl + 3 O2
1.50 mol of KClO3 decomposes.
How many grams of O2 will be produced?
(1.50 mol of KClO3/1) x (3 O2/2 mol of KClO3) x (32g / 1 mol O2) = 72 g
1.5 mol KCLO3
15.99g O2
1 Mol O2

16. Mass to Moles/ Moles to Mass15
2 KClO3 ---> 2 KCl + 3 O2
If 80.0 grams of O2 was produced, how many moles of KClO3 decomposed?
We want to produce 2.75 mol of KCl. How many grams of KClO3 would be required?
337 g of KClO3
337 g of KClO3

17. Mass to Moles/ Moles to Mass16
Practice with a friend
2 H2 + O2 ---> 2 H2O
How many grams of H2O are produced when 2.50 moles of oxygen are used?
2) If 3.00 moles of H2O are produced, how many grams of oxygen must be consumed?
3) How many moles of Li required to make 46.4 g of Li3N?
90 g of H2O
48 g of O2
6 Li(s) + N2(g)  2 Li3N(s)
46.4 g Li3N x (1 mol Li3N/34.8 g Li3N) x (6 mol Li/2 mol Li3N) = 4.00 mol Li

18. _Pb(NO3)2+ _KI_PbI2+_KNO3
Mass to Moles/ Moles to Mass 17
_Pb(NO3)2+ _KI_PbI2+_KNO3
4. How many grams of Pb(NO3)2 are needed to react completely with 9.00 mol KI?
1490g Pb(NO3)2
_CH4 + _O2  _CO2+_H2O
5. How many moles of water will be produced when 8.5 g of CH4 react with oxygen?
0.81 mol O2
2N2O5(g)  4NO2(g) + O2(g)
6. How many moles of N2O5 were used if 210g of NO2 were produced?

19. Mass to Moles/ Moles to Mass18
7. How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride?
2 Na + Cl2  2 NaCl
8. Calculate the number of moles of ethane (C2H6) needed to produce 10.0 g of water.
2 C2H6 + 7 O2  4 CO2 + 6 H20

20. Mass to Mass 4 FeS2 + 11 O2 → 2 Fe2O3 + 8 SO2 19
Std Dev Mass-Mass conversions video clip
MgCl2 (aq) AgNO3 (aq)  2 AgCl (s) + Mg(NO3)2 (aq)
How many grams of silver chloride could be produced by the complete reaction of 19.7 g of magnesium chloride with silver nitrate? 
4 FeS O2 → 2 Fe2O3 + 8 SO2
If iron pyrite, FeS2, is not removed from coal, oxygen from the air will combine with both the iron and the sulfur as coal burns. If a furnace burns an amount of coal containing 125 g of FeS2, how many grams of SO2 (an air pollutant) is produced?

21. 20
Mass TO Mass
How many grams of water can I make from 25 grams of hydrogen gas and an excess of oxygen gas, using the reaction
2 H2 + O2 2 H2O
225 grams of water

22. 21
Mass to Mass Practice
How many grams of CO2 will be produced by the combustion of 15.0 g of propane?
C3H8 (g) + 5 O2 (g) --> 3 CO2 (g) + 4 H2O (l)
How many grams of HCl are needed to react with g of Fe2O3?
Fe2O3 (s) + 6 HCl (g) --> 2 FeCl3 (s) + 3 H2O (g)

23. 22
2N2O5(g)  4NO2(g) + O2(g)
3. How many grams of N2O5 are needed to produce 75.0 grams of O2?
4. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen.
N2 + 3 H2  2 NH3

24. 2Al(s) + 6HCl(aq)  2AlCl3(aq) + 3H2(g)23
2Al(s) + 6HCl(aq)  2AlCl3(aq) H2(g)
5. How many grams of aluminum chloride can be produced when 3.45 grams of aluminum are reacted with an excess of hydrochloric acid?
2 C2H6    +  7 O2   ----->  4  CO2   +  6  H2O
6. During its combustion, ethane C2H6, combines with oxygen O2 to give carbon dioxide and water.  A sample of ethane was burned completely and the water that formed has a mass of 1.61 grams.  How many grams of ethane was in the sample?
0.90 grams of ethane

25. Download/Link Std Dev mod 7 limiting reactant24
Limiting Reactants
Download/Link Std Dev mod 7 limiting reactant
Limiting Reactant - The reactant in a chemical reaction that limits the amount of product that can be formed.  The reaction will stop when all of the limiting reactant is consumed.
Example: I want to assemble a gadget that requires one nut, one bolt and two washers for every hole. I have in my garage a bucket filled with 12 washers, 4 bolts and five nuts.
What is the LIMITING SMALL METAL OBJECT?
Goal: Demonstrate the conceptual principle of limiting reactants

26. Limiting Reactants Calculations
How To…
1-Calculate how much can be made by both.
The one with the least amount is the LR.
Example 1:
You combine 10.0 grams of hydrogen gas and 15.0 grams of oxygen gas. How many grams of water vapor are made? Which is the limiting reactant?
2H2 + O2  2H2O
Oxygen is limiting reactant, as the amount of H2O is much less than that produced by hydrogen. 25

27. Limiting Reactants 26 How To…
1-Calculate how much can be made by both.
The one with the least amount is the LR.
Limiting Reactants
Example 2:
If 5.00 grams of copper metal react with a solution containing 20.0 grams of AgNO3, which reactant is limiting and what mass silver is produced? A copper (II) product is formed. 26

28. Limiting Reactants-Practice with a friend
1) 10.0g of aluminum reacts with 35.0 grams of chlorine gas to produce aluminum chloride. Which reactant is limiting?
2 Al + 3 Cl2  2 AlCl3
CaO + 2HCl → CaCl2 + H2O
2)75 grams of calcium oxide react with 130 grams of hydrochloric acid to produce a salt and water What is the limiting reactant?   27

29. -Practice with a friend Cu (s) + 2AgNO3 (aq) → Cu(NO3)2 (aq) + 2Ag (s)
Limiting Reactants
-Practice with a friend 28
Cu (s) + 2AgNO3 (aq) → Cu(NO3)2 (aq) + 2Ag (s)
3) 5g of copper metal react with a solution containing 20g of silver nitrate to produce copper (II) nitrate and silver.
Al2S3 + 6 H2O → 2 Al(OH)3 + 3 H2S
4) g of aluminum sulfide and g of water react until the limiting reagent is consumed.

30. 29
Reversible Reactions
A reversible reaction is one in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously.
Most reactions are reversible. Some are not-
EX:
burning,
combustion.

31. Std Dev Dynamic Equilibrium30
Equilibrium
Std Dev Dynamic Equilibrium
At equilibrium, the concentration of all reactants and products stays constant.

32. 31
Dynamic Equilibrium
It seems as if nothing is happening, because the macroscopic properties, those you can see (e.g. color and temperature), do not change. However, at the microscopic level there is continual change.
No “NET” change occurs.
It is a DYNAMIC STATE
Note: When the concentration of products stays constant and the concentration of reactants stays constant, the system is at equilibrium.

33. Dynamic Equilibrium Amounts are not always 50/50 at equilibrium.32
Dynamic Equilibrium
Amounts are not always 50/50 at equilibrium.
Depends on which one is more favorable (products or reactants)
Equilibrium refers mainly to the RATE of the reaction. Not the amounts of product and reactant.

34. Factors Affecting Equilibrium:33
Factors Affecting Equilibrium:
Le Chatelier’s Principle
If stress is applied to a system in equilibrium, the system changes in a way that relieves the stress.
Adding more reactant or product
Change the temperature
Change the Pressure
Le Chatelier’s Principle
Video Clip

35. 34

36. 35

37. 36

39. Baking Soda Lab Video

40. Reaction of Stoichiometry Calculations
Fe2O3 + 3CO ----> 2Fe + 3CO2
Questions we could ask about the reaction….
Question #1:
How many CO molecules are required to react with 25 formula units of Fe2O3?
Question #2.
How many Fe atoms are produced by reaction of 2.5 x 105 formula units of Fe2O3 with excess CO?

41. Fe2O3 + 3CO ----> 2Fe + 3CO2 Question #3:
What mass of CO is required to react with 146 grams of Fe2O3?
Question #4:
What mass of CO2 can be produced by the reaction of moles of Fe2O3? …with excess CO?