In a laboratory, a student studies the absorption and transmission of light in order to analyze copper in brass and determine its percentage within the brass sample.
He determines the amount of light absorbed by a sample by measuring the amount of light transmitted, all at a particular wavelength. A standard solution of pure copper is used as well as a solution from the brass. The copper solution will be diluted several times to have varying concentrations. The absorbances of each of these known solutions at the particular wavelength are used to create a Beer's Law plot. The concentration of Cu^2+ ions in the brass sample can be calculated.
Now here are the questions:
Explain whether the following factors would increase, decrease, or not affect the percent copper in the brass sample in the experiment described above. Include a brief explanation.
1) The mass of the copper wire was recorded incorrectly larger than its actual value.
2) The mass of the brass was recorded incorrectly lower than its actual value.
3) The copper wire solution was diluted to 100 mL instead of 50 mL.
4) The copper wire and brass solutions were both diluted to 100 mL instead of 50 mL.
5) A student wet the filter paper with deionized water to hold it in place before filtering the tin (IV) oxide from the brass solution.
6) In the quantitative transfer of the standard copper solution, one drop (0.05 mL) of the solution was lost.
I'm completely lost on this. Obviously, I don't expect the answers just given to me, but I'm not sure how to even approach this. I thank anyone that can help! :)
I need help on this too
No worries! I'll explain the factors one by one and provide a brief explanation for each.
1) The mass of the copper wire was recorded incorrectly larger than its actual value.
- This factor would not affect the percent copper in the brass sample. The mass of the copper wire is not directly related to the concentration of copper in the brass sample being analyzed. The concentration is determined through the measurement of absorbance and the Beer's Law plot using the known solutions of copper.
2) The mass of the brass was recorded incorrectly lower than its actual value.
- This factor would increase the percent copper in the brass sample. If the mass of the brass is recorded as lower than its actual value, then the calculated concentration of copper in the sample would be higher than it should be. This would lead to an overestimation of the percent copper in brass.
3) The copper wire solution was diluted to 100 mL instead of 50 mL.
- This factor would decrease the percent copper in the brass sample. Diluting the copper wire solution to a larger volume would result in a lower concentration of copper in the solution. As a result, the calculated concentration of copper in the brass sample would be underestimated, leading to a lower percentage of copper in the sample.
4) The copper wire and brass solutions were both diluted to 100 mL instead of 50 mL.
- This factor would not affect the percent copper in the brass sample. The dilution of both solutions would not change the concentration of copper in the brass sample compared to the original scenario. The concentration is determined based on the absorbance measurements and the Beer's Law plot using the known copper solution.
5) A student wet the filter paper with deionized water to hold it in place before filtering the tin (IV) oxide from the brass solution.
- This factor would not affect the percent copper in the brass sample. Wetting the filter paper with deionized water does not introduce any additional copper into the sample. The filter paper is used to separate the tin (IV) oxide from the brass solution and does not influence the concentration of copper in the sample.
6) In the quantitative transfer of the standard copper solution, one drop (0.05 mL) of the solution was lost.
- This factor would decrease the percent copper in the brass sample. Losing one drop of the standard copper solution during the transfer would result in a lower volume of copper solution being used for the analysis. This would lead to an underestimation of the concentration of copper in the brass sample, resulting in a lower percentage of copper in the sample.
I hope this helps clarify the effects of each factor on the percent copper in the brass sample.