Lab: Acid-Base Properties
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 can be classified as 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 can be classified as 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. From your observations, you should be able to describe some of
the characteristic properties of acids and bases.
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. For what gas is the reaction product being tested in Part B? Part C? _____________________________
7. Give an example of each of these reactions from the investigation:
a.) neutralization: _________________________________________________________________
b.) double replacement: _____________________________________________________________
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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.
3. Using tweezers, dip a piece of pH paper into the beaker. Obtain the value of the pH by comparing
the color of the paper to a reference chart.
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. Record
the color (note: clear is not a color). Test one indicator at a time and be sure to rinse the watch
glass between uses.
5. Repeat the procedure using .5 M NaOH.
Please place used litmus and pH papers into the trashcan!
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 (magnesium, zinc, copper and iron) and 1 wood splint and
1 dry test tube.
3. Put one piece of magnesium on a watch glass. Pour a small amount of acid on the metal and
quickly invert the test tube over the metal to collect any gas produced. Insert a flaming splint.
Record reaction and 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 .5 M NaOH and record observations.
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.
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.
Part D: Neutralization
1. Add 10 drops of 1.0 M HCl to a clean watch glass. Add 1 drop of phenolphthalein. Test with pH
paper.
2. Add 1 drop of .5 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. Record the pH of the final (neutral) solution and the total number of
drops of NaOH required to change the color.
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Data and Conclusions:
Name______________________________
Part A
Red Litmus
Blue Litmus
pH paper
Phenolphthalein
HCl
1.0 M
NaOH
.5 M
Questions
1. What color would a vinegar solution be in the presence of:
a. Phenolphthalein? ____________________
b. litmus? ___________________
2. What color would an ammonia solution be in the presence of
a. Phenolphthalein? ___________________ b. litmus? ________________________
3. Which would have a higher pH, vinegar or ammonia? Why?
Part B
Magnesium
Zinc
Iron
Copper
3.0 M HCl
.5 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 not fit into your general conclusion? Why?
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3. Explain the results of the splint test.
4. Write an equation for each reaction that occurred. (Hint: The metals have a +2 charge.)
Part C
 Observations of reaction:

Observations of limewater:
Questions:
1. Write an equation for the reaction that occurred.
2. What did the limewater test for? ______________________________
3. Explain why carbonates are common ingredients in products such as Tums and Rolaids.
Part D

pH of initial solution: _______ number of drops of NaOH: _______ pH of final solution: ______
Questions:
1. Write an equation for the reaction that occurred.
2. What conclusion can be drawn about the pH of acidic, basic and neutral solutions?
3. Explain why the number of drops of HCl and the number of drops of NaOH were not the same.
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