Apr 17 9:35am G4 project day!

We are measuring the amount of CO2 dissolved in water. Firstly, we add a drop of phenolphthalein indicator to the water collected from Pedder Bay. If the solution remains colourless, we then do a titration of HI 3818-0 solution(from the equipment kit provided) against water. From the amount of solution remains in the titration syringe, we times that to a certain ratio to determine the amount of CO2. However, depending on the amount of water, it shows a different range of the amount of CO2. Our results obtained is different as well.
Amount of water: 5ml
range of measurement of CO2:0-100 mg/L
result obtained: 0 mg/L

Amount of water:10ml
range of measurement:0-50mg/L
result obtained:5.5mg/L

amount of water: 25ml
range of measurement: 0-35mg/L
result of obtained: 8.05mg/L

amount of water: 50ml
range of measurement:0-10mg/L
result obtained: 10mg/L

Because of the descrepancies of the results, we decided to repeat some of the experiment. After doing so, we have concluded that the most accurate range of measurement was the 25mL amount of water. This proved to be more consistant with the results.

Improvement: Because we took the water from different locations at the Dock, we decided to take the remaining expirements from the water table. These came to match with the 25mL result from the Dock.

25 mL Sea Table:
0.30(mg/L) x 35 = 10.5 (mg/L)
0.32 (mg/L) x 35 = 11.2 (mg/L)

The variation that we see within the experiments could be due to the agitation that the test samples were put through. The distance from the docks to the lab may have agitated the sample enough to make the inconsistancies noted in the above results. How ever, when we took the samples from the Sea Table in the Lab, the results seemed to be more congruent. This can be due to less agitation and thus release of CO2 content. Also, there is less variation in the Sea Table, because it had rained the night before and this can be added and mixed into the solution of the bay water, where as the Sea Table remains constant.

Other Results for the Docks:
Salinity: 0m- 30.7 ppt, 1m- 30.6ppt , 2m- 30.8ppt, 3m- 30.9ppt.
Temperature (degrees C): 0m- 10.7, 1m - 10.6, 2m- 9.8, 3m- 9.33
Average Dissolved O2: 10.8 (mg/L)
Transparency: 2.5m