Acid, Base, and pH Lab Name______
Problem: What is the difference between a strong or weak acid and base? How does the concentration of an acid or base change its properties?
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Notation: Acids are abbreviated HA, with the H representing the proton (H+) the acid donates to the solution. The A is referred to as the acidic anion (A-) that is left in solution as the proton is donated. HA ⇄ H+ + A- Strong Bases are abbreviated MOH, with the OH representing the hydroxide ion (OH-) the base donates to the solution. The M is cation (M+) that is left in solution as the hydroxide is donated. MOH ⇄ M+ + OH-
Procedure 1: Click on “Introduction” Begin with a strong acid and lower the pH probe into the beaker. What is the pH of this solution? Test this strong acid with the pH paper. What color does the pH indicator become? Test this strong acid with the conductivity probe. Does current travel through this solution? If so, how bright is the light bulb? Draw the bar graph for “Equilibrium Concentration”. Be sure to label your graphs! Draw a picture of the molecules/ions in the solution. Are there a lot of molecules? Are there a lot of ions? Repeat the above tests with the weak acid, the strong base, and the weak base, and water. Collect your observations in the table below: Data: Strong Acid pH meter (value) pH paper (color) Conductivity (bright/dim/none) 2.00 Red orange Bright Equilibrium Concentration Graph Picture of the ions/molecules
- + HA H2O A H3O
Weak Acid pH meter (value) pH paper (color) Conductivity (bright/dim/none)
Equilibrium Concentration Graph Picture of the ions/molecules
Strong Base pH meter (value) pH paper (color) Conductivity (bright/dim/none)
Equilibrium Concentration Graph Picture of the ions/molecules
Weak Base pH meter (value) pH paper (color) Conductivity (bright/dim/none)
Equilibrium Concentration Graph Picture of the ions/molecules
Water pH meter (value) pH paper (color) Conductivity (bright/dim/none)
Equilibrium Concentration Graph Picture of the ions/molecules
Analysis of Data: Explain the difference between a strong vs. weak acid and base.
Procedure 2: Click on “Custom Solution” This simulation allows you to change the concentration of a strong and weak acid and base. Complete the table below for some strong acids and bases and weak acids and bases by adjusting the concentration.
Data: Strong Acids Concentration Conductivity Appearance Strength pH (mol/L) (bright/dim/none) (ions/molecules) Strong 0.010 M Strong 0.050 M Strong 0.100 M Strong 1.00 M
Weak Acids Strength Concentration Conductivity Appearance pH (Approximately) (mol/L) (bright/dim/none) (ions/molecules) 0.015 M
0.150 M
0.500 M
1.00 M
Strong Bases Concentration Conductivity Appearance Strength pH (mol/L) (bright/dim/none) (ions/molecules) Strong 0.010 M Strong 0.050 M Strong 0.100 M Strong 1.00 M
Weak Bases Strength Concentration Conductivity Appearance pH (Approximately) (mol/L) (bright/dim/none) (ions/molecules) 0.015 M
0.150 M
0.500 M
1.00 M
Analysis of Data: Describe the difference between a concentrated vs. dilute acid or base solution.
Conclusion Questions:
1. A strong acid is exists primarily as molecules / as ions. (circle)
2. A weak base is a nonelectrolyte / weak electrolyte / strong electrolyte.
3. A strong base is a nonelectrolyte / weak electrolyte / strong electrolyte.
4. At the same concentration (Molarity) a strong acid will have a higher / lower / the same pH as a weak acid.
5. As concentration of a weak acid increases, the pH increases / decreases / remains constant.
6. As concentration of a weak base increases, the pH increases / decreases / remains constant.
7. As the concentration of a weak acid increases, the number of ions increases / decreases / remains constant.
8. As the concentration of a weak acid increases, conductivity increases / decreases / remains constant.
9. As the strength of a weak acid increases, the proportion of ions to molecules increases / decreases.
10. As the strength of a weak acid increases, the conductivity increases / decreases / remains constant.
11. If the pH is 6.4, the solution is a strong acid / weak acid / strong base / weak base / water.
12. If the pH is 1.2, the solution is a strong acid / weak acid / strong base / weak base / water.
13. If the pH is 11.5, the solution is a strong acid / weak acid / strong base / weak base / water.
14. If the pH is 8.1, the solution is a strong acid / weak acid / strong base / weak base / water.
15. If the pH is 7, the solution is a strong acid / weak acid / strong base / weak base / water.
16. How does that strength affect the pH of acids and bases?