Name
Feb. 27, 2015
Chemistry Lab 13: Synthesis & Decomposition Reactions
Guiding Question: How can the equation of a reaction be determined?
Learning Targets: I can predict the product(s) of a synthesis or decomposition reaction.
I can complete the balanced reaction equation.
Safety: Goggles must be worn AT ALL TIMES in this lab, even when just writing!!
When heating a substance in a test tube, be sure to point tube opening away from people.
Never directly smell or place face over chemicals.
Follow all directions carefully.
Disposal: All liquid waste in this lab can be disposed of in the sink with running water. Dry waste
should be placed directly in the garbage can.
Materials:
- Copper (II) carbonate
- Magnesium strip
- sodium bicarbonate
- calcium carbonate
Equipment
- hot plate
- test tube clamp
- Bunsen burner
- scoopula
-
Stir rod
Tongs
Crucible
3 test tubes
- copper wire
- phenolphthalein
-
250 mL beaker
Wood splints
Dropper
Test tube rack
Reference Information
Splint tests are used to detect if a gas is produced during a reaction. The following are three results
that can be obtained from performing a splint test:
Burning splint extinguishes: carbon dioxide (CO2) is a product of the reaction
Glowing splint relights: oxygen (O2) is a product of the reaction
Burning splint held over the end of a test tube creates a popping sound: hydrogen (H2) is a product
Do Now:
Tape these sheets into your lab notebook.
1. What are the steps to determining the product of a synthesis reaction? A decomposition reaction?
Procedures:
Choose one synthesis reaction, one decomposition reaction, and one other reaction of your choice to
carry out. For each reaction carried out, carefully and thoroughly record qualitative observations of
the reactant(s) and product(s). Record any information that will be needed to determine the reaction
equation later.
Reactions A and B: Synthesis
1. Obtain a hot plate/stirrer and place a beaker filled with 50 to 100 mL water on top. Turn the heat on
(maximum) and bring it to a simmer. Keep it this way until needed in step 6. Do not let too much
water evaporate, otherwise add more water.
2. Obtain a strip of magnesium that is several centimeters in length. The exact length is unimportant.
3. Turn on the Bunsen burner and light the flame. Adjust so that it is no more than a few centimeters
high.
4. Use the tongs to hold the magnesium ribbon in the flame. Give the reaction several seconds to get
started. Once it begins, do NOT look directly at the light.
5. Turn off the burner.
6. Allow the ribbon to continue reacting in the crucible. When complete, record your full observations
in the table. This ends Reaction A.
7. Collect the contents of the reaction and pour from the crucible into the beaker of hot water. Stir the
contents and note any changes that take place. Add a few drops of phenolphthalein and note any
changes that take place. This ends Reaction B. All contents may go in the sink.
Reaction C: Decomposition
1. Place two spatulas of copper (II) carbonate in a test tube.
2. In the test tube clamp, secure the test tube so that it is at a 45 degree angle and mouth pointed
upward and away from people.
3. Turn on the Bunsen burner and light the flame. Adjust so it is no more than a few centimeters high.
4. Place the burner underneath the test tube. Allow it to be heated for several minutes. Make notes of
any changes taking place.
5. Place the hot test tube in the test tube rack to cool. When cool, the contents of this test tube should
be disposed.
Reaction D: Decomposition
1. Place two spatulas of sodium bicarbonate in a test tube.
2. In the test tube clamp, secure the test tube so that it is at a 45 degree angle and mouth pointed
upward and away from people.
3. Turn on the Bunsen burner and light the flame. Adjust so it is no more than a few centimeters high.
4. Place the burner underneath the test tube. Allow it to be heated for several minutes. Make notes of
any changes taking place.
5. Obtain a wood splint and light it in the burner flame. Once lit, slowly place it in the mouth of the test
tube. Pull it back out of the mouth of the tube. Note what happens as you pull it in and out of the
tube. Also note any changes within the test tube.
6. Place the hot test tube in the test tube rack to cool. When cool, the contents of this test tube should
be disposed.
Reaction E: Synthesis
1. Take a small piece of copper wire and hold it at one end using the crucible tongs. Record its physical
properties.
2. Place the opposite end of the wire into the hottest part of the flame in the Bunsen burner (the blue
part) for 30 seconds.
3. Remove the wire and examine it. After the wire is cooled, scrape the surface with the edge of a
scoopula.
Reaction F: Decomposition
1. Place a small scoop of calcium carbonate into a test tube. If some residual powder is already in the
test tube from the last class, that is fine. Do not rinse with water.
2. Using a test tube clamp positioned near the top of the test tube, hold the test tube over a Bunsen
burner for about 5 minutes. (Safety Precautions: Point the opening of the test tube toward the
wall, away from anyone. Do not put test tube clamp in flame.)
3. Observe the products.
4. Light a wooden splint and hold it into the test tube. Observe.
5. Place the hot test tube in the test tube rack to cool.
6. Clean up: After cooled, the burned splint and matches go in trash along with powder from inside
the test tube. Do not rinse test tube. If some powder is left, that is fine.
Analysis Questions
For each reaction carried out, answer the following questions:
1. What did the reactants look like?
2. What did the products look like?
3. If you performed a splint test, why did you get the reaction you got?
4. What is the balanced chemical equation for this reaction?