Question

The blank solution used to calibrate the spectrophotometer is 10.0 mL of 0.2 M Fe(NO3)3 diluted to 25.0 mL with 0.1 M HNO3. Why is this solution preferred to simply using de-ionized water for the calibration?

Answer 1

The blank solution used to calibrate the spectrophotometer contains 0.2 M Fe(NO3)3 and 0.1 M HNO3 to reflect the composition of the actual samples and to maintain consistent ionic strength and acidity, leading to more accurate and reliable measurements.

Step-by-step explanation:

When calibrating a spectrophotometer, it is preferred to use a blank solution that is reflective of the matrix of the samples being measured. In this case, the blank solution contains not just de-ionized water but also 0.1 M HNO3 and 0.2 M Fe(NO3)3 diluted accordingly. This approach is preferred because it accounts for the absorption of the solvent and any potential interaction with the analyte.

The use of HNO3 in the calibration blank maintains a consistent ionic strength and acidity as in the samples, which can affect the absorbance readings. This method reduces background noise and leads to more accurate and reliable measurements when comparing the blank to the actual samples containing Fe³+ ions.

Answer 2

FeNCS+ product...............thats how you do it i believe