Download Type of Chemical Reactions Lab

PLEASE RETURN THIS PAPER AT THE END OF THE CLASS PERIOD !
Type of Chemical Reactions Lab - DRAFT # 3
(adapted from Lab 14 in Prentice Hall Lab Manual and Flinn Intro to Electrochemistry)
Purpose:

Observe chemical reactions and write both word and balanced chemical equations to represent
the reactions.

Use your understanding of reaction types and your lab observations to determine the product of
chemical reactions.
Materials:
Step 1
Step 2
Step 3
Step 4
iron filings (Fe(s))
lead(II) nitrate soln
(Pb(NO3)2 (aq))
potassium iodide soln
(KI(aq))
magnesium metal (Mg(s))
3 % hydrogen peroxide
(H2O2(aq))
manganese dioxide
(MnO2(s))
wood splint
matches
copper(II) sulfate soln
(CuSO4 (aq))
3M hydrochloric acid
(HCl(aq))
wood splint
matches
Step 5
0.04% bromthymol blue
indicator soln
0.5 M sodium sulfate soln
(Na2SO4 (aq))
9 V battery
carbon pencil ‘leads’
2 leads with alligator clips
2 test tube clamps
& ring stand
U-shaped tube
Safety: Googles are required for this lab  Avoid direct contact with the solutions in this lab. Hydrochloric
acid is corrosive and the lead and copper compounds are toxic when ingested. Do NOT pour the materials down
the drain – place used chemicals in the designated disposal container. Wash your hands after completing this
investigation.
Procedure:
1. Reacting iron metal and copper(II) sulfate solution
a)
b)
c)
d)
e)
Half-fill a small test tube with copper(II) sulfate solution.
Add a small amount of iron metal (pea-sized portion) to the test tube.
Mix the two substances by gently taping the bottom of the test tube on the palm of your hand.
Wait at least 5 minutes before recording observations.
Discard the materials in the designated beaker.
2. Combining lead(II) nitrate and potassium iodide solutions
a)
b)
c)
d)
Quarter-fill a small test tube with lead(II) nitrate solution.
Add 5-10 drops of potassium iodide solution.
Record your observations
Discard the materials in the designated beaker.
3. Reacting magnesium metal with hydrochloric acid
a)
b)
c)
d)
Add a small amount of magnesium metal (bean-sized portion) to a test tube.
Half-fill a small test tube with hydrochloric acid.
Record your observations.
After about 15-30 seconds, identify any gas that forms by bringing a burning wood splint to the
mouth of the test tube.
e) Record your observations.
f) Discard the contents of the test tube in the designated beaker. Wet the wood splint and throw it in
the trash can.
PLEASE RETURN THIS PAPER AT THE END OF THE CLASS PERIOD !
4. Breaking down hydrogen peroxide using a catalyst
a)
b)
c)
d)
Quarter-fill a small test tube with hydrogen peroxide solution.
Use a small funnel to add a small amount of manganese dioxide (~ ½ mini spoon) to the test tube.
Record your observations
After about 1 minute, identify any gas that forms by slowly inserting a glowing wood splint into the
mouth of the test tube. [Be careful not to drop the splint. You just want the glowing embers to reach
the gas that is being given off, not to touch the solution.]
e) Discard the contents of the test tube in the designated beaker. Wet the wood splint and throw it in
the trash can.
5.
Action of electricity on water
(Water can be broken down into its component elements by passing electricity through it.)
9 volt battery
a) Arrange the materials as shown in the diagram 
i. Use a clamp to support a U-tube on a ring stand
ii. Fill the U-tube about ½ full with a mixture of salt and indicator
1. 30 mL of 0.5 M Na2SO4 with 2 mL of bromthymol blue soln
2. This solution should be green to begin with.
If it is not, tell your teacher
3. The BTB indicator will turn blue in a base and yellow in an acid.
The formation of oxygen is accompanied by the formation of acid.
The formation of hydrogen is accompanied by the formation of base.
iii. Use the other clamp to support a 9 volt battery. Attach an alligator clip
to each terminal on the battery
iv. Connect a pencil lead to each of the alligator clips and insert one pencil
Lead into each side of the U-tube.
b) Observe and record any changes as the current flows through the system
c) for 3-5 minutes. Be sure to look the production of new materials… noting any changes in color,
smell, temperature, and/or the formation of gases or solids.
d) Clean up
i. Remove the pencil leads from the solution and disconnect the alligator clips.
ii. Disconnect the alligator clips from the battery terminals.
iii. Pour the solution from the U-tube into a beaker and swirl the contents to mix them thoroughly.
Note the final color of the indicator solution (after mixing).
iv. Return the solution to the dispensing container and rinse the U-tube with water.
v. Return the materials to their original location.
Analysis:
Complete the following for each of the reactions you observed…
1. Identify the type of reaction taking place.
2. Use the reaction type to predict the products of the chemical reaction.
3. Write the balanced chemical equation for each reaction.
a) Start by writing the formulas for each of the chemicals involved.
NOTES:
 The manganese dioxide in Rxn 4 is a catalyst – a chemical that speeds up a reaction
without being used up. The catalyst should be written above the ‘yields’ arrow. It should
NOT appear as a reactant for the reaction.
 The salt and indicator in Rxn 5 do not get included in the reaction. The salt is necessary
for the conduction of electricity and the indicator just shows us that a reaction is taking
place that changes pH. The reaction would take place without either of these present…
we just wouldn’t know it.
b) Then write the state symbols for each chemical (s, l, g, aq).
c) Then balance the equation using coefficients.