Error Analysis

Observations

The pH probe used for the titration of Gatorade with NaOH had brown sludge fixated to the inner rim that would not come off. The buffer solution that the pH probe used for the titration of Gatorade with NaOH was stored in was brown with small brown flurries suspended in it. When the pH probe was removed from the analyte solution for rinsing with distilled water, drops of the titrant solution often stuck to the pH probe in both trials. The pH probe always started its measurements at a lower number than the actual pH and slowly climbed up to the actual pH of the solution despite vigorous mixing with the stirring rod to even the composition of the analyte solution.

If the buffer solution that the pH probe was stored in had fungus or bacteria growing in it, the pH probe could have been damaged or completely saturated in a solution that could not be cleaned off with distilled water; in reference to the observations section, one of the pH probes used had brown sludge stuck to the surface. The presence of an unknown substance on the probe likely threw off the calibration process and messed with the pH readings of the analyte throughout the lab, as the unknown substance may have reacted with the analyte to create a higher voltage than expected, leading to a lower pH reading.

For each new measurement of the solution being tested, the probe would give an unusually low initial reading that was followed by a period of steadily rising pH readings that eventually plateaued out. Without the addition of any extra titrant, the pH probe would give two distinct pH measurements for the same solution. If it was assumed that the probe had leveled out its readings when it actually was still rising, a lower pH would have been recorded instead of the actual pH of the solution. The result of this error, if it happened intermittently throughout a titration, would be a more linear graph (such as the Titration of Tonic Water with 0.1 M NaOH graph), or a stair-step like graph (such as Titration of Gatorade with NaOH graph from 0mL of NaOH added to 3mL NaOH added, and Titration of Tonic Water with NaOH from 4mL of NaOH added to 12mL NaOH added). Another source of error is that some of the titrant was spilled during the titration of tonic water. This could mean that the buffer zone determined by experiment is too large, as the stable pH was due to a lack of titrant rather than the tonic water’s buffer capacity.

The pH probe often carried with it drops of analyte solution when removed for rinsing with distilled water. This inconsistency led to a smaller volume of analyte, and since pH is -log[H+] and the concentration of H+ ions depends on the volume of the analyte, the pH readings for each subsequent trial may have been slightly lower than expected. If, however, mixing the analyte with the stirring rod achieved the desired effect of evenly distributing the Gatorade and NaOH throughout the solution, then removing small drops of the analyte should have no effect on the concentration of H+ because theoretically H+ ions would also be removed when the drops of analyte clung to the pH probe.