Types of Reactions
Objective :
Introduce different types of reactions and learn to write complete and balanced equations.
Introduction:
Chemical reactions fall under a number of categories. We will use Group 1 labels to designate the basic type of reactions that occur. We will use Group 2 designations to describe the specific energy and chemical changes occurring.
Group 1: combination, decomposition, single replacement, double replacement
Group 2: redox, precipitation, gas forming, combustion, acid/base, metal + acid
Each reaction is set up as its own station; you may do the reactions in any order. However, reaction #3’s products will be used as reaction #4’s reactants, so take care not to dispose of reaction 3 until you have completed #4.
For each reaction, describe each reactant before, during and after the reaction. “water like” is an acceptable qualitative observation for a clear liquid with no smell.
If there is no immediate evidence of a reaction, add more reactants and/or wait longer. It may be a no reaction.
Procedure :
Reaction 1:
•Light your Bunsen burner and adjust the flame to high heat.
• Using crucible tongs, hold a 6 cm length of copper wire in the hottest part of the flame for a few minutes.
Reaction 2:
• Clean an iron nail with a piece of sandpaper or steel wool so the surface of the nail is shiny.
• Place the nail in a test tube and add the 0.10 M copper (II) sulfate solution so that one half of the nail is covered.
• After approximately 15 minutes, remove the nail and note any changes in both the nail and the solution. You should move onto other reactions while you are waiting.
Reaction 3
• Put ~ 2 small scoops solid copper (II) sulfate pentahydrate in a test tube.
• Using a test tube clamp, hold the test tube and contents at an angle away from yourself and your classmates. Heat the test tube, moving it back and forth gently over a Bunsen burner flame.
• Continue heating until no further change is observed. Save the contents for Reaction 4.
Reaction 4
• Allow the test tube and contents from Reaction 3 to cool.
• Use the distilled water bottle to add 3 or 4 drops of water to the test tube.
Reaction 5
• Add ~ 1mL calcium chloride solution to a test tube. To a second test tube add ~ 1mL sodium carbonate solution.
• Pour the calcium chloride solution into the test tube containing sodium carbonate solution.
Reaction 6
• Place a piece of mossy zinc in a test tube.
• Add hydrochloric acid solution to the test tube until the mossy zinc is completely covered.
Reaction 7
• Fill a test tube one-fourth full with hydrogen peroxide solution.
• Add a few grains of manganese (IV) oxide. (Note: Manganese (IV) oxide acts as a catalyst in this reaction – should it be included in the chemical equation?)
• Test the gas evolved by placing a glowing (not burning) splint into the mouth of the test tube.
Reaction 8
• Obtain a 6 cm length of copper wire and place it in a test tube one-fourth full of the lead (II) nitrate solution. Record some initial observations, then wait fifteen minutes and note any changes. You should move onto other reactions while you are waiting.
Reaction 9
• Obtain a pea-size chunk of lead metal and place it in a test tube one-fourth full of the copper (II) sulfate solution. Record some initial observations, then wait fifteen minutes and note any changes. You should move onto other reactions while you are waiting.
Reaction 10
• Obtain a pea-size chunk of lead metal and place it in a test tube one-fourth full of sulfuric acid solution. Record some initial observations, then wait fifteen minutes and note any changes. You should move onto other reactions while you are waiting.
Reaction 11
• Obtain a 6 cm length of copper wire and place it in a test tube one-fourth full of sulfuric acid solution. Record some initial observations, then wait fifteen minutes and note any changes. You should move onto other reactions while you are waiting.
Prelab (hand written in your lab notebook)
Hand write your procedure and include any empty data tables you will need during lab into your lab notebook, and answer the following.
a. If X + AB ®XB + A does occur, which is more reactive, A or X?
b. If X + AB ® XB + A does not occur, which is more reactive, A or X?
c. What type of reaction is XY + AB ® A + XB + Y according to group 1?
d. How do you determine that a reaction is a redox reaction from its chemical equation?
Postlab (handwritten in your lab notebook)
Clearly report your results, any graphs or tables, and answers to postlab questions. Include a statement of any problems/errors encountered, and a statement of what you learned from this lab.
Results:
For each reaction (1 through 11):
i. Write a balanced chemical equation. Include physical states (s, l, g, aq) for all reactants and products.
ii. Label the reaction in terms of its Group 1 designation: combination, decomposition, single replacement, or double replacement.
iii. Label the reaction in terms of its Group 2 designation(s): redox, precipitation, gas forming, combustion, acid/base, or metal + acid.
Postlab questions
1. Are all combustion reactions redox? Explain.
2. What is the difference between burning and heating? How can you tell in the lab if you are heating or burning?
3. Redox reaction involve the transfer of electrons between reactants in a reaction. But what characteristic macroscopic changes, if any, accompany a redox reaction? In other words, what are the outward signs of a redox reaction?
4. Can a reaction have more than one Group 2 designation? For instance, can a reaction be gas evolving and also be a redox reaction? Explain using an example.