Question

6. Suppose your TA gives you a test tube containing a phosphate solution of unknown concentration and asks you to analyze it. Your TA is kind enough to give you a hint: the unknown solution has a phosphate concentration between 4.00 x 105 M and 8.00 x 103M. How would your sample preparation procedure for analyzing this unknown solution differ from the sample preparation procedure for the soda pop?

Answer 1

The soda pop sample preparation involves measuring the absorbance of a sample at different wavelengths with the help of a spectrophotometer. Then a calibration curve is prepared by plotting the absorbance of different dilutions of sample at the same wavelength . The concentration of unknown can then be measured by finding the absorbance of unknown at the same wavelength using the calibration graph.

For determining the concentration of an unknown solution , initially different known concentrations of the sample are prepared and then the absorbance of the samples are measured at a particular wavelength and a calibration curve is plotted. The absorbance of the unknown sample is also measured at the same wavelength and from the calibration curve the concentration of unknown sample can be determined.

In the given sample the concentration range of unknown sample is between 4 x 10^-5 and 8 x 10^-5, so while preparing known concentrations of sample the lowest can be set as 4 x 10^-5 and highest as 8 x 10^-5​​​​​​​