Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Petricorde on June 29, 2021, 03:52:47 PM
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Hey everyone
So I'm doing a chemistry project where I measure the levels of dissolved oxygen in varying temperatures of water through the Winkler Method, but I came across a bit of an issue. If I were to heat up water, say to 35 degrees celsius, then through my prior research the amount of dissolved oxygen present in the water should decrease. My teacher recommended I perform the titration with all the water at the same temperature, however, and he said said it might be best if I were to cover the top of the beaker containing the hot water, so as not to let any oxygen get in, and then rapidly chill the water in an ice bath. We both weren't sure if this would maintain the amount of dissolved oxygen as present in the hot water, so I thought I might ask this forum. Does anyone have any ideas on whether the water would have different amounts of dissolved oxygen despite being the same temperature?
Thanks a lot!!
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Something doesn't add up. Please elaborate on what you are trying to do - and I don't mean the selected techniques, but just the main question you are trying to investigate.
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Um I'm just trying to analyze the effect of temperature on dissolved oxygen levels in water.
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I measure the levels of dissolved oxygen in varying temperatures of water through the Winkler Method, but I came across a bit of an issue. If I were to heat up water, say to 35 degrees celsius, then through my prior research the amount of dissolved oxygen present in the water should decrease. My teacher recommended I perform the titration with all the water at the same temperature, however, and he said said it might be best if I were to cover the top of the beaker containing the hot water, so as not to let any oxygen get in, and then rapidly chill the water in an ice bath. We both weren't sure if this would maintain the amount of dissolved oxygen as present in the hot water, so I thought I might ask this forum. Does anyone have any ideas on whether the water would have different amounts of dissolved oxygen despite being the same temperature?
Water samples have same temperature in the moment of analysis, but minutes earlier, samples of the water have different temperatures (30, 40, 50 C).
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Um I'm just trying to analyze the effect of temperature on dissolved oxygen levels in water.
Winkler method calls for a very specific procedure of taking samples and "stabilizing" them prior to the titration, doesn't it? Once the samples are stabilized they can be left for several hours and it doesn't matter whether their temperature changes or not.
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Prior to the titration yeah, but the water temperature would be changed prior to the addition of chemicals that fixes it.
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So you have to design your procedure in such a way you add these reagents before the temperature changes - is there any reason why you can't?
If you are trying to determine the solubility curve C vs T (from what I understand that's what you are trying to do, yes?) you should keep the water samples in a constant temperature to equilibrate them with the oxygen, add the reagents, close the bottles - and then you can safely wait with the titration till they cool down.
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I think what I'm gonna do is heat the water up to x temperature, cap it so no oxygen can get in, quickly lower the temperature with an ice bath, and then fix it with the reagents. I'm worried if I fix it while the water is still hot some other reaction may take place that might skew the results.
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@Petricorde Distilled water doesn't have any substance that might consume O2.
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I'm not planning on using distilled water
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I'm not planning on using distilled water
Then it will be better to start with blind test with freshly boiled water, to make sure it doesn't contain anything that can interfere with the final result. Boiled water should be almost oxygen free and the test can also tell you something about the behavior of the reagents at elevated temperature.
Chemistry behind the sample preparation doesn't look like it should be temperature dependent in the possible range of the samples - especially if the titration itself is carried out after cooling the samples down. Doesn't mean there can't be problems, real chemistry loves surprises.