A student dried a wet crucible with a kimwipe. A piece of kimwipe was left clinging to the inside wall of the crucible. The student did not see the piece of kimwipe when adding the NaHCO3-KCl mixture to the crucible. The crucible and its contents were weighed and subjected to three heating cooling cycles.
Could this experimental error significantly affect the percentage of NaHCO3 in the mixture?
Justify your answer with an explanation.
What were the heating/cooling cycles?
If heating was up to 100 to say 105 C, I don't think any error would be made because the piece of paper was weighed both before and after heating so any change in mass was not due to loss of the paper. If however, the temperature of at >150 C (I assume it was of the order of 250 C or do--probably changing NaHCO3 to Na2CO3 and I think that's about 270C) then the paper would be burned off. I doubt that the carbon left would be oxidized to CO2 so some carbon would remain BUT the loss in mass of the paper would add to the loss in mass due to the loss of CO2 from NaHCO3 and that would make the results for %NaHCO3 high.
Yes, this experimental error could significantly affect the percentage of NaHCO3 in the mixture. The presence of the piece of kimwipe on the inside wall of the crucible could potentially lead to contamination of the NaHCO3-KCl mixture.
During the heating and cooling cycles, the piece of kimwipe can burn and react with the NaHCO3-KCl mixture, which can result in the loss or alteration of the NaHCO3. This can lead to inaccurate measurements and subsequently affect the calculation of the percentage of NaHCO3 in the mixture.
To ensure accurate results, it is essential to minimize sources of contamination and ensure proper cleaning and handling of lab equipment, including crucibles, to avoid introducing any foreign substances that can interfere with the experiment.
To determine whether the presence of a piece of kimwipe left clinging to the inside wall of the crucible can significantly affect the percentage of NaHCO3 in the mixture, we need to consider the potential impact of the kimwipe on the measurements and calculations involved.
The presence of the kimwipe inside the crucible can introduce several sources of error:
1. Contamination: The piece of kimwipe can introduce impurities into the NaHCO3-KCl mixture. These impurities can alter the composition of the mixture, leading to inaccurate results.
2. Altered mass: Since the crucible and its contents were weighed, the presence of the kimwipe can add extra mass to the total weight. This can result in an overestimate of the total mass of the mixture, leading to an underestimated percentage of NaHCO3.
3. Incomplete reaction: During the heating and cooling cycles, the NaHCO3-KCl mixture is expected to undergo chemical reactions. However, the presence of the kimwipe can hinder the complete reaction of the mixture, affecting the final results.
Considering these factors, it is plausible that the presence of a piece of kimwipe in the crucible can significantly affect the percentage of NaHCO3 in the mixture. It can introduce impurities, alter the measured mass, and hinder the complete reaction. All of these can lead to inaccurate results when determining the percentage of NaHCO3.
To minimize such errors in future experiments, it is important to thoroughly inspect and clean all apparatus before use, ensuring they are free from any foreign objects or residues.