TYPES OF CHEMICAL REACTIONS
Purpose:
To observe chemical reactions in order to determine reaction types.
To write balanced chemical equations for each observed reaction.
Background:
In this experiment, you will learn to differentiate among four of the five general types of chemical reactions (there is no combustion reaction). From your observations, you will attempt to identify the products of each reaction and to determine the type of reaction that has taken place. The types of reactions you will consider are the following: synthesis reaction, decomposition reactions, single-replacement reactions and double-replacement reactions. A brief description of each reaction type is provided below:
Synthesis Reactions are reactions in which two or more substances combine to form a single product. The reactants may be elements or compounds, but the product is always a single compound. An example of a synthesis reaction is the reaction of sulfur trioxide and water to form sulfuric acid (this reaction produces acid rain):
SO3(aq) + H2O(l) H2SO4
Decomposition Reactions are reactions in which a single substance breaks down into two or more simpler substances. There is always a single reactant in a decomposition reaction. An example of a decomposition reaction is the breakdown of calcium carbonate upon heating:
CaCO3(s) CaO + CO2(g)
Single replacement reactions are reactions in which an element within a compound is displaced by a separate element. This type of reaction always has two reactants, one of which is always an uncombined element. An example of a replacement reaction is the reaction of zinc metal with hydrochloric acid:
Zn(s) + 2HCl (aq) ZnCl2(aq) + H2 (g)
Double Replacement Reactions are reactions in which a positive ion from one ionic compound exchanges with the positive ion of another ionic compound. These reactions typically occur in aqueous solutions and result in either the formation of a precipitate, the production of a gas, or the formation of a molecular compound such as water. And example of a double replacement reaction is the reaction that occurs between aqueous silver nitrate and aqueous sodium chloride. A white precipitate of solid silver chloride is formed in this reaction:
AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3(aq)
Procedure:
- Record all observations (color changes, gases produced, precipitates, etc.) in the appropriate box on the data table.
- Write the balanced chemical equation in the box provided and identify the reaction taking place on the appropriate line.
- You may do these in any order.
TYPES OF CHEMICAL REACTIONS
Safety Precautions:
- Wear safety goggles.
- Tie back long hair and avoid any article of clothing or jewelry that can hang down and touch chemicals and flames.
- Always maintain a clean work area and keep all materials away from flames.
- Never reach across a flame and do not touch the burner. It may be hot.
- Never leave a lighted burner unattended.
- Point a test tube or bottle that is being heated away from you and others.
- Never mix chemicals for the "Fun of it". What you produce may be dangerous, and possibly explosive.
- Never touch, taste, or smell any chemical. Many chemicals are poisonous. If you are instructed to note the fumes of an experiment, always gently wave your hand over the opening of the container and direct the fumes to your nose. Do not inhale fumes directly from a container.
- Use only those chemicals needed in the activity. Keep all lids closed when a chemical is not being used. Notify your teacher if any chemicals are spilled.
- Dispose of all chemicals as instructed by your teacher. To avoid contamination, never return chemicals to their original container.
- Keep in mind that hot glassware will not appear hot. Never pick up any glassware without first checking to see if it is hot.
- When an experiment is completed, always clean up your work area and return all equipment to its proper place.
- Wash your hands after every experiment.
- Make sure the candle is out before leaving the laboratory.
Data and Observations:
Use the data table on the backside of the procedure
Write your observations in the box entitled: “Observations”.
Conclusion:
Your discussion of the reactions will be the balanced chemical equations that you have written in the boxes entitled, “Balanced Equation” along with the type of reaction (synthesis, decomposition, single replacement double replacement, or combustion).
TYPES OF CHEMICAL REACTIONS
- CuSO4 5 H2O producesH2O(g) and CuSO4(s).
Materials: goggles, test tube, copper (II) sulfate pentahydrate, test tube holder, Bunsen burner, matches, scoopula.
- Place 3-4 crystals of copper (II) sulfate pentahydrate crystals in a test tube.
- Light your candle.
- Using a test tube holder, heat the contents overthe candle flame (the test tube should be almost parallel to the lab table).
- Heat the test tube for approximately one minute, rotating the test tube in the flame periodically. Record your observations.
- Discard the contents in the CuSO4 waste container. Wipe the outside of the test tube with a paper towel to get the soot off, clean your test tube and place it upside down in the rack to dry.
- Mg(s) and HCl(aq) to produce H2(g) and MgCl2(aq).
Materials: goggles, test tube, 3M hydrochloric acid, test tube rack, magnesium ribbon, wooden splint, Bunsen burner, matches.
- Fill a test tube one fifth full of hydrochloric acid. Place the test tube in the test tube rack.
- Get a piece of magnesium metal from the canister. Add the magnesium ribbon to the hydrochloric acid.
- Place your thumb over the mouth of the test tube to keep the gas from escaping.
- Once you feel a lot of pressure on your thumb, test for the presence of hydrogen gas by removing your thumb and placing a burning wood splint at the mouth of the test tube. Do not drop it in. Record your observations.
- Make sure the metal completely reacts and disappears.
- Discard the contents of the test tube down the sink with the water running. If there is metal left in the test tube, put it metal waste container. Clean your test tube and place it upside down in the rack to dry.
- CuSO4(aq) and K2CO3(aq) produces CuCO3(s) and K2SO4(aq)
Materials: goggles, test tube, copper (II) sulfate, potassium carbonate, two 10mL graduated cylinders
- Obtain a sample (5 mL) of copper (II) sulfate. Place it in a test tube. Record its physical properties.
- Take a sample (5 mL) of potassium carbonate. Record its physical properties.
- Mix the two solutions in the test tube. Observe and record the outcome.
- Take test tube with you to your next station. After that station is complete, check your results one more time to make sure you observed everything. If this is your last station, wait 5 minutes before making a final observation.
- Clean your test tube and place it upside down in the rack back at station C to dry.
- CaO(s) and H2O(l) combine together to make Ca(OH)2(s)
Materials: goggles, scoopula, calcium oxide, water, three test tubes, graduated cylinder, pH paper
- Using a scoopula, obtain a small sample of calcium oxide and place into test tubes #1 and test tube #2. Record its physical properties.
- To test tube #3, add 15 mL of water.
- Add 15 mL of water to test tube #2 with the calcium oxide. Record its physical properties
- Use pH paper to test the pH of each sample in each test tube (1. calcium oxide, 2. calcium oxide + water, and 3. water).
- Observe what happens to the pH of the water when it is reacted with calcium oxide.
- Pour the calcium oxide from test tube #1 back into the CaO container. Pour the other two test tubes down the sink with running water. Clean your test tubes and place them upside down in the rack to dry. Place the pH paper in the waste container.
Name ______Period _____ Date ______
Partner ______
TYPES OF CHEMICAL REACTIONS
Reaction / Observations of Reactants / Observations during Reaction and Observations of the ProductsA
B
C
D
Balance Chemical Equations for each station.
A.
B.
C.
D.