Spring Creek Alkalinity Lab Summary

Objectives: This lab examines the alkalinity of Spring Creek at the following sites: Chester County Camp, Galbraith Gap Run (at the bridge), Spring Creek at Boalsburg’s Military Museum, Spring Creek Park, Fisherman’s Paradise, Spring Creek at Bellefonte (below Buffalo Run), and Spring Creek at Milesburg, to determine how the population expansion occurring in State College has affected the watershed, along with how human land use and the area’s lithology potentially affects the creek’s alkalinity, which would change whether the creek is able to support its ecosystem. Using digital titrators and sulfuric acid, the samples collected from Spring Creek were titrated to determine the alkalinity of the water, and see if the stream needs to be rehabilitated,
First, the pH probes were calibrated using buffer solutions with known pH values of 4.01 ± 0.01 and 7.00 ± 0.01. First, the pH probes were placed in the 4.01 buffer and the probe was calibrated, then rinsed with distilled water, placed into the 7.00 buffer, and calibrated again. The pH probe was very close in its measurements, as the 4.01 ± 0.01 buffer was measured to have a pH of 4.01 ± 0.01, and the 7.00 ± 0.01 buffer was measured to have a pH of 6.87 ± 0.01. After the calibration, the samples of water were prepared for titration. The digital titrator had to be installed in the following manner. A syringe of 1.6 ± 0.1 N H2SO4 was attached to the digital titrator, by sliding it into a notch on the apparatus, and the plunger of the digital titrator was shifted until it met the end of the syringe. Next, the digital titrator was attached to the ring stand and clamped tightly to the stand. Then, the cap of the syringe was removed and a J-tube was inserted into the syringe. The J-tube was oriented so the bend of the J was submerged into the sample. The digital titrator was clicked to remove any air that was present in the J-tube, or in the head of the syringe, with a recorded the number of clicks. At the point where some of the sulfuric acid sprayed out of the tube, the clicking of the digital titrator was stopped and the digital titrator click number was reset
This graph shows the pH trends that would occur if a negative volume of acid was added to the solution, and how the volume of the added acid would change over the span of pH = 0 and pH = 14. When the pH of solution reached 7.13, the titrant was switched from an acid to a base, so the titration could continue. The features that the graph shows are a general trend of decreasing pH from 10.02 ± 0.01 to 3.5 ± 0.1. There is a slight dip in the pH as the volume of acid added increased from -0.005 ± 0.001 to 0 ± 0.0001. Once the system was switched to an acid titration, the buffering capacity of the sample can be seen. The sample buffers the added pH from 0 ± 0.0001 mL of acid added to about 0.02 ± 0.01 mL of acid added. After the solution’s pH passes this point, the solution reacts with the added acid which results in changes of pH for the sample solution, and the titration is completed. The inflection point on the curve is marked in pencil, and it signifies where the equivalence point of the titration occurs. This is present because it shows the point at which the concentration of the acid equals the concentration of the