Lab: Explorations with Acids and Bases
Name:_______________________
Objective: To determine the approximate pH of six unknown substances.
Procedure:
1. For each unknown substance, note the color, viscosity, and smell (Be careful! Some are strong!)
Record your observations in the data table.
2. Make a prediction as to the identity of the substance and if it is an acid or base. Record.
3. Dip the pH paper BRIEFLY into the cup. Compare the color of the paper to the pH chart on the vial
or box. Record.
4. Based on the pH scale, determine if the unknown is acidic or basic. Record.
Unknown Observations: Color,
#
viscosity and smell
1
2
3
4
5
6
Hypothesis:
pH
Predicted Identity
Vinegar – acetic acid 3-4
(5%)in water
Conclusion: acid
or base
acid
Ammonia
NH3 + H2O
NH4+ + OHPepsi – CO2
CO2 + H2O
Carbonic acid
Milk of Magnesia
(neutralizes acid in
esophagus and
intestine – stopping
pain) Mg+2
Lemon juice – citric
acid
10-11
base
5-6
10
Acid (weak)
(buffer in our
blood)
base
2
Acid (strong)
water
7
neutral
Analysis questions:
1. Which substances are weak bases? Strong?
2. Which substances are weak acids? Strong?
3. Which solution had the highest hydroxide ion concentration [-OH]? ______ammonia________
(most basic)
4. Which solution had the highest hydrogen ion concentration [H+]? _________lemon_______
(Hydronium, H3O+) (most acidic)
5. Did this experiment have a control? Explain your answer. Yes, water. It is neutral.
Read p. 480-481
1. Describe some characteristics of acids.
Taste sour
2. Describe some characteristics of bases.
Taste bitter, slippery (soap)
3. How does a litmus test work?
Red – acid
Blue - base
Read p. 483-485
4. What is the definition of an acid?
Substance that produces H+ ions when dissolved in water.
5. What ion do acids produce? ___________H+____________
Read p. 488-489
6. What is the definition of a base?
Substance that produces hydroxide ions when dissolved in water.
7. What ion do bases produce? ______________OH-__________
Read p. 506-507 and use Figure 14.20
8. The pH scale ranges from a pH of 0 to a pH of _____14____.
9. Acids have a pH less than ____7___.
10. Bases have a pH greater than __7____.
11. A pH of ___7____ is neutral.
12. What might the pH of strong base be? ________12_______ Strong acid? _______1,2__________
Weak base? _________8,9___________
Weak acid?_________5,6_______