How Many Reactants Does It Take to Make a Product

How many reactants does it take to make a product?

OBJECTIVES 1. To use models to simulate specific chemical reactions. 2. To write equations showing the ratio of reactants to products. 3. To predict products from a given set of reactants. 4. To classify types of reactions.

PRIOR KNOWLEDGE Remember the Law of Conservation of Energy? How might that apply to a chemical reaction?

PRE-LAB What happens when . . . 1. You leave an iron nail outside in the rain? 2. You pour hydrogen peroxide (H2O2) on a cut? 3. You put sodium in water? 4. You mix vinegar (HC2H3O2) and baking soda? 5. You burn natural gas (CH4) to heat your house?

Each of the scenarios above is an example of a chemical reaction. What happens to these reactants during a reaction? Where do they go? How do they form products? Can chemists predict what products will form? These are some questions we will explore today.

6. When you are counting elements what do the subscripts (small numbers) tell you? 7. When you are counting elements, what do the coefficients (large numbers) tell you?

MATERIALS 1 molecular model kit

EQUATIONS PART 1 PROCEDURE 1. For the first reaction, assign each element a color. 2. Use the model kit to build one of each reactant. Draw the reactants and note the number used. 3. Convert the reactants into the products. If you do not have enough reactants necessary to build all of the products, build more reactants. Keep building reactants until you have broken down all of the reactants and built them into products. You must always build products from reactants. 4. As a pair, decide who will be the “reactant builder” and who will be the “product builder.” The reactant builder is the only person allowed to get models from the kit. The product builder must get all of the products from the reactant builder, break them down, and build the products.

Target Inquiry GVSU-2007, Sarah Toman, Western Michigan Christian High School 1 OBSERVATIONS/DATA Reaction List the color Draw and note # of Draw and note # of used for each the reactants built the products built element

Ex: H2+O2H2O H = stripes O = dots 2 H2 1 O2 2 H2O Set # 1 Teacher Check

A. Mg+O2MgO

B. Fe + O2 Fe2O3 Set # 2 Teacher Check

A. H2O2 H2O + O2

B. HClO3  ClO2 + O2 + H2O Set # 3 Teacher Check

A. Na + H2O  NaOH + H2

B. Al + CuCO3  Al2(CO3)3 + Cu

Set # 4 Teacher Check

A. HC2H3O2 + NaHCO3 NaC2H3O2+ H2CO3

B. MgBr2 + Ca(OH)2  Mg(OH)2 + CaBr2

Set # 5 Teacher Check

A. CH4 + O2  CO2 + H2O

B. C2H2 + O2  CO2 + H2O

Target Inquiry GVSU-2007, Sarah Toman, Western Michigan Christian High School 2 ANALYSIS PART 1 1. For each reaction, how did the number of each element on the reactant side compare with the number of each element on the product side?

2. Is this consistent with the Law of Conservation of Mass? Why?

There were 5 sets of equations, did you notice a pattern within a set? Write your patterns or observations below

We will discuss the patterns as a class. Set # Pattern 1 2 3 4 5

3. Now that you know the scientific terms for these reaction types, go back to each set and label it.

EQUATIONS PART 2 As a lab group, go back and look at the equations you chose. Rewrite the equations and include the number of each substance used in the equation itself. Going back to our example of water, the original equation and our final tally of products and reactants is in the table below.

Initial Reaction List the color used Draw and note # of Draw and note # of Final Reaction for each element the reactants built the products built

Ex: H2+O2H2O H = stripes Ex: 2 H2+ O22 H2O O = dots 2 H2 1 O2 2 H2O This final reaction is called a balanced equation. 1. Explain why you think chemists chose this name.

2. Using your observations and data from the 10 reactions you chose, write 10 balanced equations.

3. Balance the following reaction. See if you can do it without using the kit.

Zn + HCl  ZnCl2 + H2

4. Would the reaction change if you had 3 Zn on the reactant side? If so, how?

5. Would the reaction change if you had 5 H2 on the product side? If so, how?

6. Why does changing one substance affect the others?

Target Inquiry GVSU-2007, Sarah Toman, Western Michigan Christian High School 3 Check with your teacher before moving on to part 3.

EQUATIONS PART 3 These reactions are partially balanced, complete the job. When you have written the balanced equation, identify each reaction type.

Reactants Products ___Nitrogen, ___ Oxygen 2 Nitrogen, 4 Oxygen

1. ___ N2 + ___ O2  2 NO2 Reaction Type ______

Reactants Products ___Iron, ___ Oxygen 4 Iron, 6 Oxygen

Reactants Products ____Sodium, ___ Magnesium, ___ Chlorine ___Sodium, ___ Magnesium, ___ Chlorine

2. 4 Fe + ___O2  ___Fe2O3 Reaction Type ______

3. Na + MgCl2  2 NaCl + Mg Reaction Type______

Reactants Products ___Carbon, ___Hydrogen, ___ Oxygen ___Carbon, ___Hydrogen, ___ Oxygen

4. C3H8 + O2  3 CO2 + H2O Reaction Type ______

Reactants Products ___ Lead, ___ Carbon, ___Hydrogen, ___ Lead, ___ Carbon, ___Hydrogen, ___ Oxygen, ___ Chlorine ___ Oxygen, ___ Chlorine

5. Pb(C2H3O2)2 + HCl  PbCl2 + 2 HC2H3O2 Reaction Type ______

ANALYSIS PART 3

8. How do you calculate the number of oxygen in 2 NO3 molecules?

Look at the reactants as they are forming products in equation 5.

9. What happened to the bond between Pb and C2H3O2?

10. What happened to the bond between H and Cl?

Target Inquiry GVSU-2007, Sarah Toman, Western Michigan Christian High School 4 11. What happened to the bond between C and H and O in C2H3O2?

12. What patterns do you notice with the polyatomic ions when they are in these reactions?

13. How could this pattern be helpful (or is it helpful)?

REFLECTION Think back to part 1 where you were breaking up reactants and building products.

1. What happens to the reactants during a reaction? 2. What happens to the bonds between the reactants? 3. What happens to the bonds between the products? 4. Did all of the bonds break every time? If not, what were some bonds that stayed in tact? Explain a possible reason why those bonds did not break. 5. How do the reactions form products? Can chemists predict what products will form? Explain.

GOING FURTHER Balance the following reactions and identify the type.

1. The Haber process was developed by Fritz Haber in World War I to help the Germans make their explosives. It combines nitrogen and hydrogen to make ammonia at a very high temperature and pressure.

Balanced Reaction Type

N2 + H2  NH3

2. In photosynthesis plants use energy from the sun to produce sugar. When we eat plants we can reverse this process as shown in this reaction.

C6H12O6 + CO2  CO2 + H2O

3. Limestone has been used for centuries to make buildings. When heated, it breaks down into quicklime and carbon dioxide. Limestone can also be used with heat and clay to make cement.

CaCO3  CaO + CO2

Target Inquiry GVSU-2007, Sarah Toman, Western Michigan Christian High School 5 4. The thermite reaction is used to weld the rails together on the railroad. It has also been used to ignite solid-fuel rocket motors.

Al + Fe2O3  Al2O3 + Fe

5. When storing calcium metal, it is important to keep its exposure to oxygen at a minimum. If the calcium is left sitting out on the lab bench, it will turn white on the outside as a result of the calcium reacting with oxygen in the air to yield calcium oxide.

Ca + O2  CaO

6. If you have indigestion, it may be from too much acid in your stomach. Doctors often prescribe milk of magnesia. The milk of magnesia reacts with your stomach acid and neutralizes it causing your pain to dissipate.

HCl + Mg(OH)2  MgCl2 + H2O

7. To produce silver, you could put solid zinc in a solution of silver (II) sulfate.

Zn + Ag2SO4  ZnSO4 + Ag

8. When you are using propane on the grill at home, the reaction of the propane looks like this reaction.

C3H8 + O2  CO2 + H2O

9. The decomposition of water yields hydrogen and oxygen gas. Isn’t it interesting how water, which can be used to extinguish many fires, can also be used to produce two very explosive substances?

H2O  H2 + O2

Target Inquiry GVSU-2007, Sarah Toman, Western Michigan Christian High School 6