Lab on Determining hard water
Not sure if I answered this currently, not completely sure how to explain either.
If a student has a non-zero blank correction, but forgets to include that correction in his/her calculations:? a. Would his/her calculated [EDTA] be correct, too high, or too low? b. Would his/her calculated [Ca] in the unknown be correct, too high, or too low?
Not quite sure if my answers are right:
A. EDTA would be a too high
B. Calculate would be low
To determine the correctness of the calculated [EDTA] and [Ca] in the unknown when a student has a non-zero blank correction but forgets to include that correction in the calculations, we need to understand the concepts involved and the steps of the procedure. Here's an explanation of how to derive the answers:
1. Understanding the blank correction: In the lab, a blank correction is performed to account for any impurities or contaminations present in the reagents used or the equipment. It is done by running a control sample (blank) without the analyte, in this case, the water sample being tested for hardness. The value obtained in the blank is then subtracted from the subsequent measurements to eliminate any interferences.
2. Calculating [EDTA]: The concentration of ethylenediaminetetraacetic acid (EDTA) in the titration solution determines the hardness of the water sample. EDTA reacts with the calcium ions present in hard water, forming a complex that changes color at the endpoint. The volume and concentration of the EDTA solution used in the titration are used to determine the water's hardness.
Now, let's analyze the effects of forgetting to include the non-zero blank correction:
a. Calculated [EDTA]: If the student forgets to include the blank correction, the calculated [EDTA] would be too high. This is because the blank value, which represents impurities or contaminations, should have been subtracted from the titration value to obtain an accurate result. By not considering the blank correction, the student would overestimate the concentration of EDTA in the solution, leading to an artificially high calculated value.
b. Calculated [Ca] in the unknown: Forgetting to include the blank correction would result in the calculated [Ca] in the unknown being too low. Since the blank correction accounts for any interferences or impurities, not subtracting it means failing to account for these factors, leading to an artificially lower concentration of calcium ions in the water sample.
In summary:
a. The calculated [EDTA] would be too high if the student forgets to include the non-zero blank correction.
b. The calculated [Ca] in the unknown would be too low if the student forgets to include the non-zero blank correction.
It is important to emphasize the significance of accurately accounting for the blank correction to obtain reliable and precise results in the determination of hard water.