Method
Prior to the experiment, the LabQuest must be set up and the conductivity probe must be calibrated. Calibrate the conductivity probe connected to a LabQuest using a solution of known conductivity. In this experiment, a solution with a conductivity of 1000 μS/cm was used. Choose “Calibrate” from the menu and choose “Calibrate Now”. Then submerge the conductivity probe into the standard solution and type in the known value of the solution; 1000 in this case. Then, wait for the voltage to stabilize and press “Keep”. Exit by pressing “OK” when this process is done. Set the data collection method on the LabQuest to “events with entry”.
In order to titrate the phosphoric acid, the following method was used. Using a pipette, transfer 60ml
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Start the titration and keep titrating in 0.5ml intervals until the graph shows the end point. Transfer the data from the LabQuest to a computer using a USB key and then open the file to select the values which is used to obtain the graph below. Pipette 20ml of the phosphoric acid into an Erlenmeyer flask and add 3 drops of Thymol blue indicator. Perform a titration using NaOH solution. Repeat the experiment.
The cola drinks were titrated using the following method: Prepare the beverage in a 250ml volumetric flask. Use a funnel to facilitate the process. Place the beaker on a hot plate so that it boils and place a watch glass on top to prevent the carbon dioxide from the atmosphere getting dissolved in the cola. Once the cola starts to boil, continue to boil it for another 10 minutes so that the carbon dioxide is removed. When the cola has finished boiling, cool it in an ice bath and pour the cola back in the volumetric flask and use distilled water to fill the flask to compensate for the evaporated water. Using a volumetric pipette, transfer 60ml of the cola to a beaker and put the magnetic stirrer in the beaker. Submerge the conductivity probe in the cola. Fill up the burette with NaOH
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If a large amount of the indicator was added, it was possible to slightly distinguish the color. However, this wasn’t clear enough to properly distinguish the end point of the