Question

In an experiment where you standardize EDTA with calcium carbonate and then have EDTA as the titrant and zinc as the analyte to determine the amount of zinc, which of the following are potential sources of error in the determination of the mean and relative standard deviation for the amount of zinc in your unknown?

Select all answers that apply.

1) Lack of homogeneity in the indicator solution

2) Not dissolving calcium carbonate completely

3) Inconsistencies in pipetting the zinc unknown

4) Systematic error in the buret calibrations

5) Failing to quantitatively transfer calcium carbonate

6) Sharing the indicator bottle

7) Over-titrating

Answer 1

The sources of errors are:

1. The inhomogeneity of the indicator as if the indicator is localised( not completely homogeneous throughout the solution) it may not take the concentration of the rest of the soluton into consideration while showing its colour change.

2. While standardising, the concentration of Calcium carbonate should be constant throuout. If there remainsany insoluble particles which may get solubilize after a certain period of time may lead to standardisation error.

3. Inconsistencies in pipetting Zn solution, will lead to different amount of EDTA titrant volume leadin6to an error.

4. Systematic error in burette calibration will also lead to an error where the volume of the titrant remains variable and while calculating the concentration, the error never comes into the good range.

5. If the carbonate solution is not transferred properly, then there will be a error as the expected concentration of calcium carbonate would not be same as practically and standardisation error will come into picture.