Factors That Affect the Ph of a Solution

Problem: What effect do different temperatures have on the pH of 0.10 mol/L hydrochloric acid?

Variables:

        Controlled-    The type of pH probe being used

• The length of time that you let the pH meter settle on a pH for
• They type of thermometer probe being used to check the temperature of the 0.10 mol/L hydrochloric acid
• The volume of 0.10 mol/L hydrochloric acid being tested

        Responding/Dependent- The acidity of the 0.10mol/L hydrochloric acid

Manipulated/Independent- The temperature of the 0.10 mol/L        hydrochloric acid

Materials:

• Hot plate
• Vernier LabQuest pH probe
• Vernier LabQuest temperature probe
• 1 150.0  mL beaker
• Ice
• 500.0 mL beaker
• Graduated pipet
• Pipet bulb
• 25.0 mL 0.10 mol/L hydrochloric acid

Procedure:

1. Rinse and dry the 150.0 mL beaker, 500.0 mL beaker and the graduated pipet
2. Using the graduated pipet measure out a volume of 25.0 mL of the 0.10 mol/L hydrochloric acid and put it into the 150.0 beaker.
3. Record the physical properties of the hydrochloric acid in table 1.
4. Using the Vernier LabQuest Probe plug in both the pH probe and the temperature probe.
5. With the temperature probe put it into the 25.0 mL of 0.10 mol/L hydrochloric acid and measure its temperature. Make sure that the probe does not touch the sides of the bottom of the beaker. Record this temperature in table 1.
6. Then take out the temperature probe and put in the pH probe and record the pH of the hydrochloric acid in table 1. Make sure that the probe does not touch the sides of the bottom of the beaker.
7. Place 2 handfuls of ice into the 500.0 mL beaker
8. Then place the beaker containing the 25.0 mL of the 0.10 mol/L hydrochloric acid into the ice and wait for approximately 10 minutes.
9. When the 10 minutes are up measure look at the hydrochloric acid and record the physical properties of the hydrochloric acid in table 1.
10. With the temperature probe put it into the 25.0 mL of 0.10 mol/L hydrochloric acid and measure its temperature. Make sure that the probe does not touch the sides of the bottom of the beaker. Record this temperature in table 1.
11. Then take out the temperature probe and put in the pH probe and record the pH of the hydrochloric acid in table 1. Make sure that the probe does not touch the sides of the bottom of the beaker.
12. Then take the beaker out of the ice and leave it on the lab counter for 2 minutes.
13. When the 2 minutes are up measure look at the hydrochloric acid and record the physical properties of the hydrochloric acid in table 1.
14. With the temperature probe put it into the 25.0 mL of 0.10 mol/L hydrochloric acid and measure its temperature. Make sure that the probe does not touch the sides of the bottom of the beaker. Record this temperature in table 1.
15. Then take out the temperature probe and put in the pH probe and record the pH of the hydrochloric acid in table 1. Make sure that the probe does not touch the sides of the bottom of the beaker.
16. After you have recorded those measurements place the beaker onto a hot plate that has been plugged in. Turn the hot plate on and set it at 2.
17.  Hold the Vernier temperature probe into the beaker and wait until the temperature of the 25.0 mL of the 0.10 mol/L hydrochloric acid inside to become stable. Make sure that the probe does not touch the sides or bottom of the beaker.
18. When the temperature has stabilized record this temperature in table 1. Then take out the temperature probe and put in the pH probe. Get the pH reading and then record this pH reading table 1.
19. Record the physical properties of the 25.0mL of 0.10 mol/L hydrochloric acid in table 1.
20. Then turn the hotplate setting to 5 and Hold the Vernier temperature probe into the beaker and wait until the temperature of the 25.0 mL of the 0.10 mol/L hydrochloric acid inside to become stable. Make sure that the temperature probe does not touch the bottom or sides of the beaker.
21. When the temperature has stabilized record this temperature in table 1. Then take out the temperature probe and put in the pH probe. Get the pH reading and then record this pH reading table 1.
22. Record the physical properties of the 25.0mL of 0.10 mol/L hydrochloric acid in table 1.

Observations

Table 1: The physical properties of a 0.10 mol/L hydrochloric acid solution, HCl(aq). The pH temperature, ºC, that the pH is being tested at, and the pH at that temperature. Also included in this table is the volume of the HCl(aq) being tested.