Documents
Resources
Learning Center
Upload
Plans & pricing Sign in
Sign Out

Lab-1--Chemical-Reactions-Pre-Lab

VIEWS: 31 PAGES: 4

									CHEMISTRY                                                              LAB DATE: 2/2/2010
Lab 1: Types of Chemical Reactions
_____________________________________________________________________________________
PURPOSE:
To identify and classify chemical reactions based on five general categories.


BACKGROUND:
       Although countless chemical reactions exist, nearly all of them can be classified into a
few specific categories. In this experiment, you will learn to differentiate five general types of
chemical reactions. From observations, you will identify the products of each reaction and
determine the type of reaction that has taken place. You will consider the following reaction
types: combination reactions, decomposition reactions, single-replacement reactions, double-
replacement reaction, and combustion reactions.

       Each lab station will take between 10-15 minutes – if you finish the experiment ahead of
time, use the remaining time to begin your post-lab write-up. Make sure to read the
introductions to each section before starting the lab. There may be some information in there to
help you with the questions!


MATERIALS:
  - Safety goggles                                       -   250 mL beaker
  - Bunsen burner                                        -   Sodium bicarbonate
  - Crucible tongs                                       -   Fume hood
  - Magnesium ribbon                                     -   0.25 M KI solution
  - Electrolysis apparatus                               -   0.125 M Pb(NO3)2 solution
  - Small beaker of aqueous salt solution                -   3 watch glasses
  - Mossy zinc                                           -   Ethanol
  - 5 M nitric acid                                      -   Matches
  - Rubber gloves                                        -   Limewater (saturated solution of
  - 5 plastic disposable pipettes                            CaO)
  - 10 mL beaker                                         -   Small test tube


PRECAUTIONS & SAFETY PROCEDURES:
  - Goggles must be worn at all times.
  - Magnesium is flammable and burns at very high temperatures, necessitating a higher
    level of fire safety than is usual.
  - Nitric acid is extremely corrosive and causes slow-healing burns upon contact with bare
    skin. For this reason, gloves should be worn when working with nitric acid and
    countertops should be wiped down with a paper towel soaked in sodium bicarbonate.
  - Compounds containing lead are extremely toxic, although they are safe to handle with
    bare skin as long as they are cleaned off quickly with soap and water. Countertops
    should be wiped down with a paper towel so that no yellow precipitate is visible.
  - Ethanol is extremely flammable and should be handled carefully. Ethanol fumes are also
    extremely toxic and should be avoided.


                                                                                                     1
   -   Limewater is generally not hazardous in normal handling, however good laboratory
       practices should always be used. Avoid long term exposure to skin or by inhalation or
       ingestion. If ingestion occurs, induce vomiting after drinking 2 glasses of water.
   -   Notify the instructor if any major spills occur.
   -   Dispose of broken glass in the sharps container and NOT in the regular trash bin.
   -   Exercise caution when working with an open flame.
   -   Wash your hands thoroughly after completing this experiment.


LAB PROCEDURE:
Station 1:
   1. Obtain a small piece of magnesium ribbon.
   2. Light a Bunsen burner, making sure it has been adjusted so a bright blue cone of flame is
       visible.
   3. Using your crucible tongs, hold the magnesium ribbon directly over the blue cone of the
       Bunsen burner flame until the reaction starts. Don’t worry—you’ll know when it happens!
       Record your observations.
   4. Clean-up: Dispose of white powder residue in the trash.


Station 2:
   1. Place the end of a cathode and the end of an anode into a beaker of salt water. Record
       your observations.
   2. Clean-up: Dry the ends of the electrodes with a paper towel and wipe down any droplets
       of water.




Station 3:
CAUTION: This experiment should be done in a fume hood. Gloves must be worn at this station!
   1. Place a chunk of zinc into the 10 mL beaker.
   2. Pill a pipette of 5M nitric acid and carefully squirt it into the 10 mL beaker. Record your
       observations.
   3. Clean-up: When the reaction has stopped, carefully pour the contents of the 10 mL
       beaker into the 250 mL beaker containing sodium bicarbonate. This will neutralize the
       remaining nitric acid. Wipe the countertop in the fume hood with a paper towel to ensure
       that no nitric acid droplets remain.

Station 4:
                                                                                                2
   1. In a watch glass, place 5 drops of 0.25 M potassium iodide solution using the labeled
      pipette.
   2. Add 5 drops of 0.125 Pb(NO3)2 solution using the labeled pipette. Record your
      observations.
   3. Clean-up: Rinse the residue into the labeled disposal container.

Station 5:
   1. Place about 10 drops of ethanol into a watch glass with a pipette.
   2. Light and drop a match into the ethanol, making sure not to put your hand too close to the
       flame. Record your observations.
   3. Clean-up: Once everything has cooled, throw the match into the trash.

Station 6:
   1. Fill half a small test tube with limewater, using a pipette.
   2. Place a straw into the test tube.
   3. Blow into the straw for at least 15 seconds, making sure to EXHALE ONLY. Alert the
       instructor immediately if limewater is ingested.
   4. Record your observations.
   5. Clean-up: Throw away the straw and empty the contents of the test tube into the sink.
       Rinse out the test tube with a few drops of fresh limewater and pour out the excess.




                                                                                              3
CHEMISTRY                                                                         LAB DATE: 2/2/2010
Lab 1: Types of Chemical Reactions
POST-LAB
_____________________________________________________________________________________
RESULTS/DISCUSSION:
        In addition to the instructions laid out in the ―Lab Notebook Instructions‖ worksheet, answer the following
questions in the results and discussion section:
Note: DO NOT answer these in bullet point form.
   - What are some indicators that a chemical reaction has taken place?
   - Classify each of the observed reactions as one of the five reaction types.
   - Write a balanced equation for each reaction observed. (Include catalysts.)
   - In Station 2, sodium chloride is not a reactant in the chemical reaction. However the addition of an
        electrolyte, such as table salt, aids in ―jumpstarting‖ the reaction and is known as a catalyst. What makes
        table salt a good catalyst in this reaction?

GRADING:
Introduction & Purpose      5 pts
Pre-lab procedure                  5 pts
Material & Safety Procedure 5 pts
Procedure                          5 pts
Data & Observations         10 pts
Results/Discussion                 20 pts
Conclusion                         10 pts
Neatness & organization            5 pts
Following directions               5 pts
_________________________________
TOTAL POSSIBLE:                    70 pts




                                                                                                                      4

								
To top