diff --git a/Acid_Neutralizing_Capacity/Acid_Neutralizing_Capacity.rst b/Acid_Neutralizing_Capacity/Acid_Neutralizing_Capacity.rst index 121f4204..6cc8e1f6 100644 --- a/Acid_Neutralizing_Capacity/Acid_Neutralizing_Capacity.rst +++ b/Acid_Neutralizing_Capacity/Acid_Neutralizing_Capacity.rst @@ -194,22 +194,37 @@ Procedures .. |ProCoDA_save_gran| image:: ../ProCoDA/Images/Gran_save.png +Determine ANC of a Known Sample +------------------------------- + +#. Measure approximately 50 mL of reverse osmosis water (ANC = 0 meq/L) in a 100 mL beaker using an electronic balance. +#. Place the beaker on the magnetic stirrer, add a stir bar and stir slowly. +#. Place the pH electrode in the solution. +#. Analyze the sample using :ref:`Gran plot analysis `. Add 0.05 N HCl (the titrant) using a digital pipette in increments suggested by ProCoDA (or smaller). +#. Save the Gran data by selecting |ProCoDA_save_gran|. The data will be saved in a tab delimited format. You will use this data to plot a titration curve and to verify that the Gran technique accurately measures the ANC of a sample. + +If the error is greater than 0.1 meq/L (equal to an error of 0.1 mL titrant) then check your pipette technique using a balance, verify that you ended the titration process correctly with a high correlation coefficient, and then repeat the titration. + Determine ANC of Acid Rain Samples ---------------------------------- Determine the ANC for all samples collected from the Acid Lake Remediation lab. Start with 50 mL from the t=0 sample and run through the procedure to learn how the software works. Then repeat the procedure with 50 mL from the t=0 sample and for remaining samples with the goal of making an accurate ANC measurement and creating an accurate titration curve by using 0.100 mL titrant increments throughout the entire titration. Remember that the biggest source of error for this lab will likely be poor pipette techniques. - #. Measure 50 mL of an acid lake sample in a graduated cylinder or using an electronic balance. - #. Add to a 100 mL beaker. + #. Measure approximately 50 mL of a sample in a 100 mL beaker using an electronic balance. #. Place the beaker on the magnetic stirrer, add a stir bar and stir slowly. #. Place the pH electrode in the solution. #. If the initial pH is less than 4.5 no titration is necessary and equation :eq:`eq_Gran_pH_lt4` can be used to calculate the ANC. #. Record the initial pH (prior to adding any titrant) and initial sample volume. - #. Analyze the sample using :ref:`Gran plot analysis `. Add 0.05 N HCl (the titrant) using a digital pipette in increments of 0.100 mL. - #. Save the Gran data to ``S:\Courses\4530\Group #\ANC\Gran`` by selecting |ProCoDA_save_gran|. The data will be saved in a tab delimited format. You will use this data to plot a titration curve and to verify that the Gran technique accurately measures the ANC of a sample. - #. Record the ANC and the equivalent volume. + #. Analyze the sample using :ref:`Gran plot analysis `. Add 0.05 N HCl (the titrant) using a digital pipette in increments suggested by ProCoDA (or smaller). + #. Save the Gran data by selecting |ProCoDA_save_gran|. The data will be saved in a tab delimited format. You will use this data to plot a titration curve and to verify that the Gran technique accurately measures the ANC of a sample. + + Clean Up + ======== - If the error is greater than 2\% then check your pipette technique using a balance and then repeat the titration. + #. Empty and rinse sample bottles and place them on the drying racks. + #. Rinse the pH probe with reverse osmosis water + #. Reinstall the pH probe in the small bottle that ensures that the pH probe is maintained moist in a low pH solution (can be pH buffer 4.0). + #. Put away all of the equipment except for the ProCoDA box. .. _heading_ANC_Prelab_Questions: diff --git a/Acid_Rain/Acid_Rain.rst b/Acid_Rain/Acid_Rain.rst index 00721f9d..02347dd7 100644 --- a/Acid_Rain/Acid_Rain.rst +++ b/Acid_Rain/Acid_Rain.rst @@ -301,6 +301,20 @@ We will use a pH probe to measure pH in this experiment. The pH probes are store #. Measure the lake volume. This can be done in a large graduated cylinder OR by taking the mass of the water in the lake. Which would be more accurate? #. Repeat the experiment and change one of the following parameters: stirring, initial ANC, ANC source (use :math:`CaCO_3` instead of :math:`NaHCO_3`), or amount of ANC added. + Clean Up + ======== + + #. Empty lake into sink, rinse with DI water, store in cabinet at your workstation + #. Rinse all plastic tubing and place in a drawer at your workstation + #. Rinse metal tubes and place in the top drawer + #. Place peristaltic pump (and pump tubing) in a cabinet at your workstation + #. Keep stirrer on your benchtop for use next week + #. Keep samples on your benchtop for analysis next week + #. Rinse pH probe, insert into bottle cap (add buffer 4 if empty) and keep on your benchtop + #. Empty and rinse Jerrican and place along the wall of windows (remove label) + #. Rinse gray PVC pipe and place in top drawer + #. Put your data files somewhere accessible + .. _table_Acid_pump_tubing: @@ -381,7 +395,10 @@ Data Analysis Questions ========= - #. What do you think would happen if enough :math:`NaHCO_3` were added to the lake to maintain an ANC greater than :math:`50 \mu eq/L` for 3 residence times with the stirrer turned off? How much :math:`NaHCO_3` would need to be added? + #. What do you think would happen if enough :math:`NaHCO_3` were added to the lake to maintain an ANC greater than :math:`50 \mu eq/L` for 3 residence times with the stirrer turned off? Here are a few things to consider. + #. How much :math:`NaHCO_3` would need to be added? + #. What is the density of sodium bicarbonate? + #. Given the density of sodium bicarbonate, what will happen to the sodium bicarbonate when it is added to the lake? #. What are some of the complicating factors you might find in attempting to remediate a lake using :math:`CaCO_3`? Below is a list of issues to consider. #. extent of mixing #. solubility of :math:`CaCO_3` (find the solubility and compare with :math:`NaHCO_3`) diff --git a/Laboratory_Measurements/Laboratory_Measurements.rst b/Laboratory_Measurements/Laboratory_Measurements.rst index 3f642cc7..60dcf1f5 100644 --- a/Laboratory_Measurements/Laboratory_Measurements.rst +++ b/Laboratory_Measurements/Laboratory_Measurements.rst @@ -166,6 +166,18 @@ Create a standard curve and measure an unknown #. Save **AND** export the calibration data from ProCoDA (|photometer_open_save_export|). These calibration curves will be useful later in this course! #. Measure the concentration of the unknown concentration of red dye. Note that you can do this directly in ProCoDA in the Graphs tab. +Clean Up +======== + + #. Empty and rinse red dye bottles and place them on the drying racks. + #. Empty and rinse volumetric flasks and place them on the drying racks. + #. Place pipette tips in the pipette disposal mini cans + #. Discard any used weighing boats + #. Pull DI water through the photometer to rinse it and then place it in your drawer. + #. Rinse temperature probe and place it in your drawer + #. Empty and rinse unknown red dye solutions + #. Place concentrated red dye in your drawer + .. _heading_Laboratory_Measurements_and_Procedures_Pre-Laboratory_Questions: @@ -185,8 +197,8 @@ Submit the `spreadsheet <../_static/Datasheet.xlsx>`_ containing the data sheet, #. Fill out the attached `spreadsheet <../_static/Datasheet.xlsx>`_. Make sure that all calculated values are entered in the spreadsheet as equations. All remaining analysis for the course will be done in Atom using Python! - #. Create a graph of absorbance vs. concentration of red dye ``\#40`` in Atom/Markdown using the exported data file. Does absorbance increase linearly with concentration of the red dye? Remove data points from the graph that are outside of the linear region. - #. What is the value of the extinction coefficient, :math:`\varepsilon`? + #. Create a graph of absorbance vs. concentration of red dye ``\#40`` in Atom/Markdown using the exported data file. Does absorbance increase linearly with concentration of the red dye? Remove data points from the graph that are outside of the linear region (absorbance too high for the detector to measure accurately). + #. What is the value of the extinction coefficient, :math:`\varepsilon`? Use the slope of the absorbance vs concentration to calculate the absorbance. The pathlength for the sample cell is given in the :ref:`photometer section `. #. Did you use interpolation or extrapolation to get the concentration of the unknown? #. What measurement controls the accuracy of the density measurement for the NaCl solution? #. What density did you expect (see prelab 2)?