Week 4

• Read pages 108 - 120 in lab manual.

• Review lectures slides on pH and properties of water (posted in D2L Week 4 Content).

• Review textbook chapter 20 as needed.

Videos on pH concepts and pH meter use:

• Calibration of pH meter: https://www.ncbionetwork.org/educational-resources/videos/ph-meter-calibration

• pH: http://www.youtube.com/watch?v=Xeuyc55LqiY

• Buffers: https://www.youtube.com/watch?v=ZLKEjXbCU30

Fischer Scientific Accumet pH meters: https://www.fishersci.com/us/en/brands/IL3X6IN2/accumet.html

• Note: We have models AB15 and AB150 in our lab.

• We have two types of electrodes (Catalog #'s 13-620-299A and 13-620-183A).

Factors affecting pH:

• Effect of temperature on pH: http://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Acids_and_Bases/Aqueous_Solutions/The_pH_Scale/Temperature_Dependent_of_the_pH_of_pure_Water

• Impact of CO2 in water: https://www.youtube.com/watch?v=X3VdcLD6h9w

City of Portland pH disposal requirements: https://www.portlandoregon.gov/citycode/28861

• Cannot dispose of materials that "have a pH of less than 5.0 or more than 11.5" ...

• Before class on Day 1 and 2:

  • No pre-lab assignment.

• Before class on Day 3:

  • Bring a sample of water from your home (500mL or more - bring in disposable container, or transfer from a reusable water bottle to a beaker when you arrive in lab).

  • Upload your data template for the pH analysis assignment (D2L Assignments tab).

• LE #9, Part A (Calibration and use of pH meter)

  • Identify the model of pH meter at your assigned equipment station and review the SOP and instruction manual.

  • Watch the demonstration video on pH meter calibration.

  • Complete Part A (pages 118-119) with the following modifications:

    • Step A.5.1: Calibrate the pH meter yourself.

      • Ask the instructor over to your station to review the pH meter calibration with you.

    • Step A.5.2: Measure two unknown solutions.

  • Submit your data to the class data Google Sheet.

• LE #9, Part C (Factors affecting pH measurements)

  • Refer to the LE9 Data Template posted in D2L, Week 4 Content.

  • When following the instructions in the manual, adjust the frequency and type of measurements to complete the tables in the data template.

  • Submit your data from part C using the link in D2L, Week 4 Content.

  • Document this as Entry #5 in Benchling. In your discussion section, answer questions 2 to 6 from the lab manual.

• Analysis of Home Water Sample

  • Bring 500+ mL of water from your home in a disposable container.

  • Refer to the protocol posted in D2L, Week 4 Content.

  • Create a data table for the activity and upload this to D2L Assignments before beginning any data collection.

  • Document this as Entry #6 in Benchling. In your discussion section, refer to the questions listed in the protocol.

• Demonstrate your pH meter calibration technique and results to the instructor.

• Use the Class Data links (D2L, Week 4 Content) to share your data from LE #9 Part A and Part C.

• Complete entries #5 and #6 this week.

• Using a different pH meter model at another equipment station, follow the SOP instructions and calibrate the meter. Take pH measurements of 1-2 unknown solutions. Verify that you can repeatably obtain accurate pH measurements. Troubleshoot your technique, equipment function, and impact of environmental variables when pH measurements vary.

• We will continue our work with pH meters and will also be using conductivity meters.