I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was..
36.4% NaCl
36.4% SiO2
40.9% CaCO3
the total % recovered was 113.7% with a 13.7% error. I do not understand how we recovered more that the original sample. One of the post lab questions ask
1. List possible manipulation errors that might contribute to the following errors:
-obtaining a significant larger amount of NaCl than as present in the original sample;
-Obtaining a significant small amount SiO2 than was present in the original sample.
help me please! I thought maybe the physical form of the NaCl changed the mass after the boiling off process, I have also thought about the chemical bonding process, but it doesn't make an sense to me.
See this.
http://www.jiskha.com/display.cgi?id=1391564392
It's great that you're thinking about possible reasons for the errors you encountered in your lab results. Let's try to break down these errors and explore some possible explanations for each:
1. Obtaining a significantly larger amount of NaCl than present in the original sample:
- Manipulation Error: One potential manipulation error could be the loss of other compounds during the separation process, leading to a higher percentage of NaCl in the recovered mixture. For example, if some SiO2 or CaCO3 was lost during filtration or washing steps, it would result in a higher percentage of NaCl in the final product.
- Chemical Property: Another explanation could be that some chemical reactions occurred during the separation process. For instance, if there was a reaction that generated additional NaCl, it could contribute to the higher percentage obtained. However, this is less likely compared to manipulation errors.
2. Obtaining a significantly smaller amount of SiO2 than present in the original sample:
- Manipulation Error: Similarly, the loss of SiO2 during separation could explain the lower percentage obtained. If some of the SiO2 particles were not fully transferred from one container to another during the process or were left behind on the filter paper, this would result in a lower recovery of SiO2.
- Physical Property: The physical properties of SiO2, such as its grain size, shape, and density, can also contribute to measurement errors. If the SiO2 particles were very fine or porous, they could have been carried away during filtration or washing steps, leading to a lower recovery.
It's important to note that the explanations provided above are just possibilities and would require further investigation to confirm. When performing experiments, it's crucial to carefully follow the procedure, take accurate measurements, and analyze the potential sources of errors. Additionally, considering multiple factors such as manipulation errors, chemical properties, and physical properties can help narrow down the possible sources of discrepancies in your lab results.