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

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Presentation on theme: "1 STOY-KEE-AHM-EH-TREE Stoichiometry is the part of chemistry that studies amounts of substances that are involved in reactions."— Presentation transcript:

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2 1 STOY-KEE-AHM-EH-TREE Stoichiometry is the part of chemistry that studies amounts of substances that are involved in reactions.

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

4 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 AgNO 3 How many moles are there in grams of sodium phosphate (Na 3 PO 4 )? How many grams are in 5.6 x atoms of Zinc? Before we start…let’s review….. 3

5 Practice with a Friend 1.What is the mass of 7.50 moles of sulfur dioxide (SO 2 )? 2.How many moles are there in 21.4 grams of nitrogen gas (N 2 )? 3.How many moles are there in grams of sodium phosphate (Na 3 PO 4 )? 4.How many calcium atoms would be in a 100 gram sample of calcium metal? 5. Find the mass in grams of 7.5  atoms of nickel. 4

6 2HCl + Ba(OH) 2  2H 2 O + BaCl coefficients give MOLAR RATIOS 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. “amounts of substances that are involved in reactions” 5 What are some molar ratio we can write from this equation?

7 Stoichiometry “amounts of substances that are involved in reactions” What do we know from this equation? there is: one mole of CH 4 for every two moles of H 2 O there is: one mole of CH 4 for every one mole of CO 2 there are: 2 molecules of O 2 for every one molecule of CO 2 there are even: four atoms of H in CH 4 for every two atoms of O in 2H 2 O 6

8 How can we write these as conversion factors? Stoichiometry CH 4 + 2O 2  CO 2 + 2H 2 O there is: one mole of CH 4 for every two moles of H 2 O there are: 2 molecules of O 2 for every one molecule of CO 2 there are even: four atoms of H in CH 4 for every two atoms of O in 2H 2 O 7

9 1) C 3 H 8 + 5O 2  3CO 2 + 4H 2 O What do we know from the balanced equation? 1 molecule of propane for every 3 molecules of CO 2 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 mg S ----> 87.9 mg FeS 5.58 g of Fe g of S ----> 8.79 g of FeS Now you try: Write as many conversion factors as you can Stoichiometry 8

10 Our goal.. To be able to determine amounts of products and reactants…moles and grams….for ANY chemical reaction. Cutesy….but GOOD… video clip about mole conversions.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……… 2 CH 3 OH (l) + 3 O 2 (g) --> 2 CO 2 (g) + 4 H 2 O (l)

11 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 N 2 + 3H 2 → 2NH 3 How many moles of hydrogen are needed to completely react with 2.0 moles of nitrogen? 2KClO 3 → 2KCl + 3O 2 How many moles of oxygen are produced by the decomposition of 6.0 moles of potassium chlorate?

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

13 Mole to Mole Practice Silver can be made according to the following equation : 2AgNO 3 + Ca  Ca(NO 3 ) 2 + 2Ag -If 35.3 moles of silver nitrate are reacted how many moles of silver are produced? 11

14 Mole to Mole Practice with a Friend Use the following equation to answer the questions below: 2 CH 3 OH (l) + 3 O 2 (g) --> 2 CO 2 (g) + 4 H 2 O (l) 1.How many moles of water will be produced from the combustion of 0.27 moles of CH 3 OH? 2.How many moles of O 2 are needed to burn 2.56 moles of CH 3 OH? 3.How many moles of CO 2 are produced from the combustion of 5.25 moles of CH 3 OH? 4.How many moles of water are produced when 3.25 moles of CO 2 are formed? 0.54 mol H 2 O 3.84 mol O mol CO mol H 2 O 12

15 When N 2 O 5 is heated, it decomposes: 2N 2 O 5 (g)  4NO 2 (g) + O 2 (g) 5. How many moles of NO 2 can be produced from 4.3 moles of N 2 O 5 ? = moles NO mol N2O5N2O How many moles of O 2 can be produced from 4.3 moles of N 2 O 5 ? = moles O mol N2O5N2O5 2.2 Mole to Mole Practice with a Friend 13

16 Mass to Moles/ Moles to Mass 14 2 KClO 3 ---> 2 KCl + 3 O mol of KClO 3 decomposes. –How many grams of O 2 will be produced? (1.50 mol of KClO 3 /1) x (3 O 2 /2 mol of KClO 3 ) x (32g / 1 mol O 2 ) = 72 g 1.5 mol KCLO g O 2 1 Mol O 2

17 If 80.0 grams of O 2 was produced, how many moles of KClO 3 decomposed? We want to produce 2.75 mol of KCl. How many grams of KClO 3 would be required? Mass to Moles/ Moles to Mass 2 KClO 3 ---> 2 KCl + 3 O g of KClO 3 15

18 Practice with a friend 1)How many grams of H 2 O are produced when 2.50 moles of oxygen are used? 2) If 3.00 moles of H 2 O are produced, how many grams of oxygen must be consumed? 3) How many moles of Li required to make 46.4 g of Li 3 N? Mass to Moles/ Moles to Mass 2 H 2 + O 2 ---> 2 H 2 O 90 g of H2O 48 g of O2 6 Li(s) + N 2 (g)  2 Li 3 N(s) 46.4 g Li 3 N x (1 mol Li 3 N/34.8 g Li 3 N) x (6 mol Li/2 mol Li 3 N) = 4.00 mol Li 16

19 Mass to Moles/ Moles to Mass _Pb(NO 3 ) 2 + _KI  _PbI 2 +_KNO 3 4. How many grams of Pb(NO 3 ) 2 are needed to react completely with 9.00 mol KI? 1490g Pb(NO 3 ) 2 _CH 4 + _O 2  _CO 2 +_H 2 O 0.81 mol O 2 5. How many moles of water will be produced when 8.5 g of CH 4 react with oxygen? 6. How many moles of N 2 O 5 were used if 210g of NO 2 were produced? 2N 2 O 5 (g)  4NO 2 (g) + O 2 (g) 17

20 Mass to Moles/ Moles to Mass 7. How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride? 2 Na + Cl 2  2 NaCl 8. Calculate the number of moles of ethane (C 2 H 6 ) needed to produce 10.0 g of water. 2 C 2 H O 2  4 CO H

21 MgCl 2 (aq) + 2 AgNO 3 (aq)  2 AgCl (s) + Mg(NO 3 ) 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? Mass to Mass 4 FeS O 2 → 2 Fe 2 O SO 2 If iron pyrite, FeS 2, 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 FeS 2, how many grams of SO 2 (an air pollutant) is produced? Std Dev Mass-Mass conversions video clip 19

22 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 H 2 + O 2  2 H 2 O 225 grams of water 20

23 Mass to Mass Practice 1.How many grams of CO 2 will be produced by the combustion of 15.0 g of propane? C 3 H 8 (g) + 5 O 2 (g) --> 3 CO 2 (g) + 4 H 2 O (l) 2.How many grams of HCl are needed to react with g of Fe 2 O 3? Fe 2 O 3 (s) + 6 HCl (g) --> 2 FeCl 3 (s) + 3 H 2 O (g) 21

24 2N 2 O 5 (g)  4NO 2 (g) + O 2 (g) 3. How many grams of N 2 O 5 are needed to produce 75.0 grams of O 2 ? 4. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. N H 2  2 NH 3 22

25 6. During its combustion, ethane C 2 H 6, combines with oxygen O 2 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 2 C 2 H O > 4 CO H 2 O 2Al(s) + 6HCl(aq)  2AlCl 3 (aq) + 3H 2 (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? 23

26 Limiting Reactants 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. Goal: Demonstrate the conceptual principle of limiting reactants 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? Download/Link Std Dev mod 7 limiting reactant 24

27 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? Limiting Reactants Calculations 2H 2 + O 2  2H 2 O %20text.pdf Oxygen is limiting reactant, as the amount of H2O is much less than that produced by hydrogen. How To… 1-Calculate how much can be made by both. The one with the least amount is the LR. 25

28 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. Limiting Reactants How To… 1-Calculate how much can be made by both. The one with the least amount is the LR. 26

29 1) 10.0g of aluminum reacts with 35.0 grams of chlorine gas to produce aluminum chloride. Which reactant is limiting? 2 Al + 3 Cl 2  2 AlCl 3 CaO + 2HCl → CaCl 2 + H 2 O 2)75 grams of calcium oxide react with 130 grams of hydrochloric acid to produce a salt and water. What is the limiting reactant? Limiting Reactants- Practice with a friend 27

30 Limiting Reactants -Practice with a friend 28 3) 5g of copper metal react with a solution containing 20g of silver nitrate to produce copper (II) nitrate and silver. Cu (s) + 2AgNO 3 (aq) → Cu(NO 3 ) 2 (aq) + 2Ag (s) 4) g of aluminum sulfide and g of water react until the limiting reagent is consumed. Al 2 S H 2 O → 2 Al(OH) H 2 S

31 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. 29

32 Equilibrium At equilibrium, the concentration of all reactants and products stays constant. Std Dev Dynamic Equilibrium 30

33 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. Dynamic Equilibrium 31

34 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. Dynamic Equilibrium 32

35 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. 1.Adding more reactant or product 2.Change the temperature 3.Change the Pressure Le Chatelier’s Principle Video Clip 33

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40 Baking Soda Lab Video

41 Questions we could ask about the reaction…. Question #1: How many CO molecules are required to react with 25 formula units of Fe 2 O 3 ? Fe 2 O 3 + 3CO ----> 2Fe + 3CO 2 Question #2. How many Fe atoms are produced by reaction of 2.5 x 10 5 formula units of Fe 2 O 3 with excess CO? Reaction of Stoichiometry Calculations

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


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