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.
triplicate
When analyzing your lab results, it is indeed unusual to recover more than the original amount of the compounds. However, there are several possible explanations for this discrepancy. Here are some manipulation errors that could have contributed to obtaining a larger amount of NaCl and a smaller amount of SiO2 than originally present:
1. Experimental error: It is possible that there were errors in your measurements or calculations during the lab. Small inaccuracies can accumulate and lead to a significant difference in the final percentages.
2. Contamination: If there was any contamination during the separation process, it could have affected the measurements. For example, if some NaCl particles were inadvertently introduced into the SiO2 sample or vice versa, it would lead to incorrect measurements and skewed percentages.
3. Loss of volatile compounds: If any of the compounds in the mixture were volatile (easily evaporated), they might have been lost during the separation process. This could result in an artificially higher percentage of the non-volatile compounds like NaCl, leading to an overestimation of its original amount.
4. Incomplete separation: If the separation techniques used in the lab were not perfectly efficient, some compounds might not have been fully separated. For instance, if some SiO2 remained in the CaCO3 fraction, it would lead to an underestimation of the SiO2 percentage.
Regarding your thoughts about the physical form of NaCl or the chemical bonding process, they are unlikely to be the main reasons for the discrepancies. Changes in physical form or bonding usually do not affect the total mass of the compound unless there are reactions that result in the formation of additional compounds.
To determine the specific reasons for the errors, it would be helpful to review your lab procedures, calculations, and the quality of the separation techniques used. It is also advisable to consult with your lab instructor for further clarification and guidance.