Why the addition of NH3 should be precise in spectrophotometer reading? What if it gives darker color?
NH3 in what? darker color than what? What experiment are you doing? Details?
Spectrophotometer. 2 ml of NH3 is added to Cu(NO3)2 to give it dark blue color. If we accidantely put 3 ml of NH3, would the absorbance reading by spec should be considered? Explain.
I wrote we shouldn't consider the reading because it will give darker color than it should be and the reading would be beyond the expected range. Is that right?
You don't have all of the experimental details written for me; however, my best guess is that the NH3 is not the limiting reagent. That is, I suspect that the experiment is to eventually determine Cu and adding NH3 gives the dark blue color. If I'm right about that then 2 mL NH3 is enough to complex ALL of the Cu ion and still have NH3 left over. I don't know the total volume but I don't think 1 mL out of several will make too much difference except for the dilution. It won't make it darker but it could dilute it enough to be a little less intense color.
The addition of NH3 (ammonia) in spectrophotometer readings should be precise for accurate results because it acts as a complexing agent or ligand. It forms a complex with the analyte, changing its chemical structure and altering its absorbance characteristics. This complex formation is crucial for many colorimetric and spectrophotometric analyses.
If NH3 gives a darker color, it may indicate an excess amount of the complexing agent. In such cases, it is important to adjust the amount of NH3 precisely to ensure the formation of the optimal complex. Adding an excess amount of NH3 can result in the formation of more complexes than required, leading to an overestimation of the analyte concentration. On the other hand, insufficient NH3 can result in the formation of fewer complexes, resulting in an underestimation of the analyte concentration.
To ensure precise addition of NH3 in spectrophotometer readings, the following steps can be followed:
1. Prepare a standard solution: Prepare a known concentration of the analyte in a sample solution.
2. Dilute the sample: If the concentration of the analyte in the sample solution is higher than the linear range of the spectrophotometer, dilute the sample solution to bring it within the linear range.
3. Set the wavelength: Select the appropriate wavelength for the analysis based on the absorbance characteristics of the analyte and its complex with NH3.
4. Zero the spectrophotometer: Set the spectrophotometer to zero absorbance using a blank solution, which does not contain the analyte.
5. Add NH3: With a pipette, add a precise volume of NH3 to the sample solution. It is important to ensure the NH3 is added dropwise while stirring the solution, ensuring thorough mixing.
6. Wait for color development: Allow the solution to equilibrate for a specific duration to allow the complex formation between the analyte and NH3. This waiting time may vary based on the reaction kinetics and analyte properties. Follow the instructions provided in the analysis protocol.
7. Measure absorbance: After the waiting period, measure the absorbance of the solution using the spectrophotometer. The spectrophotometer will provide a reading based on the intensity of light absorbed by the complex formed.
By following these steps precisely, you can ensure accurate spectrophotometer readings that reflect the concentration of the analyte in the sample solution.