Landolt Iodine Clock Reaction: Oxidation Of Bisulphite
This experiment was a Landolt Iodine clock reaction - Oxidation of Bisulphite by Iodate. It involved conducting three measured experiments. The first variable tested was concencentration. This was tested by conducting two experiments, each varying the concentration of either the NaHSO3 or KIO3. The varying of NaHSO3 involved using 0.1 Molar of KIO3 against decreasing concentrations of NaHSO3 (0.25 M, 0.125 M, 0.0625 M and 0.03125 M). When decreasing the concentration of KIO3, 0.25 M of NaHSO3 was used against the KIO3 (0.1 M, 0.05 M, 0.025 M, 0.0125 M). The final variable tested was temperature. A heat plate was used to test the clock reaction of 0.25 M NaHSO3 and 0.05 M KIO3 at temperatures of 30, 35 and 40 degrees celsius.
The experimental data found that as the concentration was decreased by half each time, the rate of reaction lengthened. This is keeping with Le Chatelier’s Principle. The model for the graph of concentration vs time for both NaHSO3 and KIO3 are also noted to be exponential decay functions. This shows that as the concentration and amount of reactant decreases, the time it takes to react lessens. When testing the temperature, it was found that as the temperature increased the reaction took less time to occur. This is also in line …show more content…
with Le Chatelier’s Principle. Because of this, the reaction shifts to the right to compensate, causing the reaction rate to increase. This reaction is a second order reaction. This is because it has two concentrations being tested and the powers add to 2. The solution changes to a deep blue colour because of the iodine and starch. In the reaction the bisulphite runs out first. This leaves the iodate to turn some of the iodide into iodine. This forms I3-. This then reacts with the starch, turning the solution blue. ("Iodine Clock (slow motion) - Periodic Table of Videos", 2018)
An experiment at (School of Mathematics and Statistics� University of Birmingham� Edgbaston� B�� �TT Birmingham�) completed a number of different clock reactions. One clock reaction tested was the iodine� bisulphate clock reaction. There experiment found that when the concentration of the clock reaction is small, the rate of reaction is short. This is inline with our experiment and findings. There experiment also stated that an idoine bisulphate clock reaction undergoes autocatalysis. An autocatalysis reaction means that the reaction product is itself the catalyst for that reaction. ("Autocatalysis", 2018)
Another experiment tested potassium iodate and sodium hydrogen sulfite.
Their experiment also tested heat using calorimetry. It was concluded that their results were linear and no reaction occured when the NaHSO3 was high. This lack of reaction can be attributed to the concentration of the NaHSO3 being too high to react with not enough KIO3 reactant to change the solutions colour. Their findings of linear results differ to our experiment as well as others. Their process involved other steps that are different to how our experiment was conducted. They also were testing for heat while we tested how temperature varied reaction rate. Their molar values were also larger than our experiment. (Kawahito, J., & Fujieda, S,
1993)
The hypothesis was found to be supported by the experiments data. It was hypothesised that lower concentrations would cause quicker reactions rates and higher temperatures would lead to quicker reaction rates. For the test of 0.25 M NaHSO3 against changing concentration of KIO3, the time the clock reaction took to occur increased as the concentrations lowered.For the test of 0.1 M KIO3 with altering concentrations of NaHSO3, the reaction continued to take longer to occur as the concentrations lowered. For the testing of increasing temperature on 0.05 M of KIO3 and 0.25 M NaHSO3, the hypothesis was supported. As the temperature increased the rate of reaction lowered. Through this it can be seen that the hypothesis was supported. The experiment can be used to justify that landolt iodine clock reactions obey Le Chatelier’s Principle. It can also be said that by lowering the concentration, the time for the reaction to occur lengthens and vice versa.
In the experimental design phase it was originally planned that the concentrations would be lowered in a less precise way. It was suggested to use a line of test tubes, each time tipping half out into the next tube and filling the remainder with water. This works in theory but is not a precise form of measurement. This would have caused the calculations and results to be skewed. As well as this, the experiment would not be easily replicated each time. This issue was fixed by using calculations and measuring equipment. Plastic pipettes were utilised to measure out precise amounts. The same people measured the chemicals each time as well as poured the solutions together. This kept the experiment under similar conditions each time. Another issue that was found was that when the reaction occurred, the solution would not change colour within a few seconds. The deep blue-purple colour was found to swirl slowly in from the outer edges over a few seconds. This caused confusion as to when to stop the stopwatch as the reaction was not instant. To fix this, the person pouring the chemicals in would swirl the beaker slightly after pouring. This resulted in the reaction occuring as a clock reaction should. The colour change would happen without swirling or taking seconds to change. As well as this, it was decided that the stopwatch would be stopped once the solution changed colour completely. When it came to measuring the amounts needed for the NaHSO3 concentration varying test, problems with the measuring arised. In an effort to use as little resources as possible due to demand, the measurements for the experiment were below 1mL. The experiment was attempted using a plastic pipette and guessing, but the results varied more than what is ideal. To fix this, electronic pipettes were used instead. This meant the measurements were precise and the results more accurate.
For future experiments, electronic pipettes are recommended. Also the use of glass pipettes instead of plastic ones. It was noted that throughout the experiment the plastic pipettes were used for the concentration varying tests. This is not recommended due to their deformed shapes and lack of precision. Also testing more temperatures is suggested. A greater scope of temperatures both above and below room temperature would yield more usable and accurate results.
Clock reactions are currently used in medicine. They are used in effervescent tablets such as Berocca and other commercial vitamin supplements. The vitamin c tablet reaction with water uses Mg(II), Zn(II), Fe(II), Mn(II), Cu(II) and Mo(VI). This reactions works by having the iodine “reduced by conversion of ascorbic acid to dehydroascorbic acid,” and once the ascorbic acid is consumed, the solution changes colour due to the iodine. A series of different amounts of ascorbic acid were used to make varying solutions. This experiment used bromate ion-iodide ion-ascorbic acid for it’s landolt clock reaction. The reaction doesn’t instantly ‘clock’ as a landolt one does due to the nature of the effervescent tablets. Instead they fizz in water until fully reacted. This leaves the water coloured and flavoured. (Kova´Cs-Hadady, K., & Fa´Bia´N, I, 1996)
The experimental data found that as the concentration was decreased by half each time, the rate of reaction lengthened. This is keeping with Le Chatelier’s Principle. The model for the graph of concentration vs time for both NaHSO3 and KIO3 are also noted to be exponential decay functions. This shows that as the concentration and amount of reactant decreases, the time it takes to react lessens. When testing the temperature, it was found that as the temperature increased the reaction took less time to occur. This is also in line …show more content…
with Le Chatelier’s Principle. Because of this, the reaction shifts to the right to compensate, causing the reaction rate to increase. This reaction is a second order reaction. This is because it has two concentrations being tested and the powers add to 2. The solution changes to a deep blue colour because of the iodine and starch. In the reaction the bisulphite runs out first. This leaves the iodate to turn some of the iodide into iodine. This forms I3-. This then reacts with the starch, turning the solution blue. ("Iodine Clock (slow motion) - Periodic Table of Videos", 2018)
An experiment at (School of Mathematics and Statistics� University of Birmingham� Edgbaston� B�� �TT Birmingham�) completed a number of different clock reactions. One clock reaction tested was the iodine� bisulphate clock reaction. There experiment found that when the concentration of the clock reaction is small, the rate of reaction is short. This is inline with our experiment and findings. There experiment also stated that an idoine bisulphate clock reaction undergoes autocatalysis. An autocatalysis reaction means that the reaction product is itself the catalyst for that reaction. ("Autocatalysis", 2018)
Another experiment tested potassium iodate and sodium hydrogen sulfite.
Their experiment also tested heat using calorimetry. It was concluded that their results were linear and no reaction occured when the NaHSO3 was high. This lack of reaction can be attributed to the concentration of the NaHSO3 being too high to react with not enough KIO3 reactant to change the solutions colour. Their findings of linear results differ to our experiment as well as others. Their process involved other steps that are different to how our experiment was conducted. They also were testing for heat while we tested how temperature varied reaction rate. Their molar values were also larger than our experiment. (Kawahito, J., & Fujieda, S,
1993)
The hypothesis was found to be supported by the experiments data. It was hypothesised that lower concentrations would cause quicker reactions rates and higher temperatures would lead to quicker reaction rates. For the test of 0.25 M NaHSO3 against changing concentration of KIO3, the time the clock reaction took to occur increased as the concentrations lowered.For the test of 0.1 M KIO3 with altering concentrations of NaHSO3, the reaction continued to take longer to occur as the concentrations lowered. For the testing of increasing temperature on 0.05 M of KIO3 and 0.25 M NaHSO3, the hypothesis was supported. As the temperature increased the rate of reaction lowered. Through this it can be seen that the hypothesis was supported. The experiment can be used to justify that landolt iodine clock reactions obey Le Chatelier’s Principle. It can also be said that by lowering the concentration, the time for the reaction to occur lengthens and vice versa.
In the experimental design phase it was originally planned that the concentrations would be lowered in a less precise way. It was suggested to use a line of test tubes, each time tipping half out into the next tube and filling the remainder with water. This works in theory but is not a precise form of measurement. This would have caused the calculations and results to be skewed. As well as this, the experiment would not be easily replicated each time. This issue was fixed by using calculations and measuring equipment. Plastic pipettes were utilised to measure out precise amounts. The same people measured the chemicals each time as well as poured the solutions together. This kept the experiment under similar conditions each time. Another issue that was found was that when the reaction occurred, the solution would not change colour within a few seconds. The deep blue-purple colour was found to swirl slowly in from the outer edges over a few seconds. This caused confusion as to when to stop the stopwatch as the reaction was not instant. To fix this, the person pouring the chemicals in would swirl the beaker slightly after pouring. This resulted in the reaction occuring as a clock reaction should. The colour change would happen without swirling or taking seconds to change. As well as this, it was decided that the stopwatch would be stopped once the solution changed colour completely. When it came to measuring the amounts needed for the NaHSO3 concentration varying test, problems with the measuring arised. In an effort to use as little resources as possible due to demand, the measurements for the experiment were below 1mL. The experiment was attempted using a plastic pipette and guessing, but the results varied more than what is ideal. To fix this, electronic pipettes were used instead. This meant the measurements were precise and the results more accurate.
For future experiments, electronic pipettes are recommended. Also the use of glass pipettes instead of plastic ones. It was noted that throughout the experiment the plastic pipettes were used for the concentration varying tests. This is not recommended due to their deformed shapes and lack of precision. Also testing more temperatures is suggested. A greater scope of temperatures both above and below room temperature would yield more usable and accurate results.
Clock reactions are currently used in medicine. They are used in effervescent tablets such as Berocca and other commercial vitamin supplements. The vitamin c tablet reaction with water uses Mg(II), Zn(II), Fe(II), Mn(II), Cu(II) and Mo(VI). This reactions works by having the iodine “reduced by conversion of ascorbic acid to dehydroascorbic acid,” and once the ascorbic acid is consumed, the solution changes colour due to the iodine. A series of different amounts of ascorbic acid were used to make varying solutions. This experiment used bromate ion-iodide ion-ascorbic acid for it’s landolt clock reaction. The reaction doesn’t instantly ‘clock’ as a landolt one does due to the nature of the effervescent tablets. Instead they fizz in water until fully reacted. This leaves the water coloured and flavoured. (Kova´Cs-Hadady, K., & Fa´Bia´N, I, 1996)