Acid-Base Properties Lab
Name________________________________
Period________Date____________________
Introduction: Acids and bases are common chemicals in everyday life. Many products from shampoos
to fruit juices, from medicines to cleaning agents derive much of their usefulness from their activity as
acids and bases. Acids are substances that ionize in aqueous solutions to produce hydronium ions, H3O+.
Acids react with metals to produce hydrogen gas and turn litmus paper red. Bases are substances that
dissociate in aqueous solutions to produce hydroxide ions, OH-. Bases turn litmus paper blue and feel
slippery. The strengths of acids and bases depend on the extent to which they ionize, or dissociate.
Strong acids or bases dissociate almost completely, while weak acids or bases dissociate to a lesser
degree.
In this investigation you will observe some reactions of acids and bases with each other, with other
compounds, and with various indicators. Indicators are weak acid or base dyes whose colors are sensitive
to H+ concentration. Avoid skin contact with HCl, be sure to wear goggles throughout the experiment.
Pre-Lab Questions:
1. What is an acid? ____________________________________________________________________
__________________________________________________________________________________
2. What is a base? ______________________________________________________________________
__________________________________________________________________________________
3. What is an indicator? What indicators will you be using in this experiment?______________________
___________________________________________________________________________________
___________________________________________________________________________________
4. Write balanced chemical equations for the reactions that occur when the following solutions are mixed:
a.) HNO3(aq)
+
NaOH(aq)
→
___________________________________________
b.) 2HCl(aq)
+
Ca(OH)2(aq)
→
___________________________________________
5. What safety precautions need to be observed when handling acids and bases? ____________________
__________________________________________________________________________________
6. What gas causes a burning splint to “pop”? ______ What gas causes limewater to turn cloudy? ______
7. Give an example of each of these reactions from the investigation:
a.) neutralization: (use reaction from part D)____________________________________________
b.) double replacement: (use reaction from Part C)_______________________________________
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Part A: Acid-Base Indicators
1. Pour 15 mL of 1.0 M HCl into a small beaker.
2. Support a piece of red litmus paper with tweezers and dip it into the beaker. Record the color.
Repeat with blue litmus paper. Record the color.
3. Using tweezers, dip a piece of pH paper into the beaker. Obtain the value of the pH (not just the
color) by comparing the color of the paper to a reference chart. Record in the data table.
4. Test each of the remaining indicators, phenolphthalein, bromothymol blue, and methyl orange
by pouring a small amount of the acid on a watch glass and adding 1 drop of the indicator (note:
clear is not a color – record “colorless”.) Test one indicator at a time and be sure to rinse the
watch glass between uses. Record in the data table.
5. Repeat the procedure using 0.50 M NaOH.
DISPOSAL: Please place used litmus and pH papers into the trash!
Part B: Reactions with metals
1. Pour 20 mL of 3.0 M HCl into a small beaker.
2. Obtain 2 pieces of the following metals: Mg, Zn, Cu and Fe, 1 wood splint, 2 dry test tubes and
matches. (Note: iron should be a very small scoop of iron fillings in a small weigh boat.)
3. Put one piece of magnesium in the test tube in the rack. Pour about 5 mL of acid on the Mg and
quickly invert another test tube over the metal to collect any gas produced (hold it with a test tube
clamp.) Insert a flaming splint in the inverted tube. Record splint observations.
4. Test the other 3 metals with acids in the same manner described in procedure 3, but do not conduct
the splint tests on these metals. A positive result for each test is bubbles forming.
5. Test each of the remaining pieces of the four metals with 0.50 M NaOH and record observations.
Again, a positive result for each test is bubbles forming. Do NOT conduct the splint test with NaOH.
DISPOSAL: Do NOT put metals in the sink! Pour metals and liquids in the TRASH!
Part C: Reaction of acids with carbonates
1. Fill a small test tube half way with limewater.
2. Add 3 scoops of calcium carbonate to a large test tube.
3. Obtain a stopper assembly. Place the stopper into the large test tube and the rubber tubing into
the test tube with the limewater. Be sure the rubber tubing is under the level of the limewater.
4. Lift off the stopper and add enough 3.0 M HCl to cover the powder. Quickly return the stopper.
5. Record observations of the reaction and changes in the limewater.
6. Quickly return the stopper assembly for others to use.
DISPOSAL: Test tube contents may be rinsed down the sink with water.
Part D: Neutralization
1. Add 10 drops of 1.0 M HCl to a clean, dry watch glass. Add 1 drop of phenolphthalein.
2. Test with pH paper and record the initial pH in the data table.
3. Add 1 drop of 0.50 M NaOH to the watch glass. Gently swirl the glass to mix the contents.
Continue to add the NaOH 1 drop at a time (count the drops), swirling after each drop, until there
is a permanent color change.
4. Record the pH of the final (neutral) solution and the total number of drops of NaOH required to
change the color.
DISPOSAL: Please place used pH papers into the trash!
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Data and Conclusions:
Name______________________________
Part A
red litmus
blue litmus
pH paper
phenolphthalein
bromothymol
methyl orange
blue
HCl
1.0 M
NaOH
0.50 M
Questions:
1. What color would a vinegar (HC2H3O2) solution be in the presence of:
a. phenolphthalein? ____________________
b. methyl orange? ____________________
2. What color would an ammonia solution (NH4OH) be in the presence of
a. bromothymol blue? ___________________ b. litmus? __________________________
3. Which would have a higher pH, vinegar or ammonia? Why?
Part B
magnesium
zinc
iron
copper
3.0 M
HCl
0.50 M
NaOH
Questions:
1. What general conclusion can be drawn regarding acids and bases and their ability to react with
metals?
2. Did any metal(s) not fit into your general conclusion? List them. Why don’t they react?
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3. Explain the results of the splint test – what was formed and what happened?
4. Write an equation for each reaction that occurred. (Hint: each metals has a +2 charge.)
Part C

Observations of reaction:

Observations of limewater:
Questions:
1. Write an equation for the reaction that occurred. Hint: it is double replacement, but one of the
products makes 2 gases giving a total of 3 products.
2. What gas did the limewater test for? _______
3. Explain why carbonates are common ingredients in products such as Tums and Rolaids. What
action do they have on stomach acids? Use correct vocabulary from the chapter.
Part D




pH of initial solution:
number of drops of HCl:
number of drops of NaOH:
pH of final solution:
_______
_______
_______
_______
Questions:
1. Write an equation for the reaction that occurred.
2. What is the pH range for acids? ______________bases? ______________ neutral? _______
3. Explain why the number of drops of HCl and the number of drops of NaOH were not the same.
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