What are some experimental errors associated with spectrophotommetry?

In summary, the conversation is about determining experimental errors in an experiment to find the equilibrium constant of the reaction Fe 3+ + SCN - = FeSCN 2+ using spectrophotometry. The participants used Fe(NO3)3 and KSCN to supply the necessary ions, but there may be excess K+ and KNO3 in the final solution which could affect the absorbance reading. One participant also suggests that blanking the spectrophotometer before each reading could improve accuracy. The conversation ends with a question about other potential sources of error and improvements for the lab experiment.
  • #1
omgwtfitsp
8
0
This isn't an actual calculation homework problem I'm having but rather a lab discussion.

I'm trying to find experimental errors of the experiment where you determine an equilibrium constant using spectrophotometry.

The reaction is: Fe 3+ + SCN - = FeSCN 2+

we used Fe(NO3)3 - iron (3) nitrate to supply Fe 3+
and KSCN - potassium thiocyanate to supply the SCN-

So in the final solution there would be some KNO3 i assume, and excess K+.


The only thing I can think of is possibly that, having those other ions in the solution when measuring absorbance of FeSCN2+ will affect the reading because those other ions ...reflect light? So far I tried looking and it came up often that KNO3 as K+ ion are clear and colourless so that means they reflect all light right?

So the spectrophotometer is set at 447 nm, where FeSCN2+ is sensitive to absorb.

So would what I said above be a reasonable source of error? I just thought that having ions that will reflect the 447 nm wavelength will affect the absorbance reading.

Are there other sources of errors and improvements one can make to this lab experiment?
 
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  • #2
Well did you blank the spec before using it to make a reading? Cause that could cause some issues. I blank it before every reading.
 

FAQ: What are some experimental errors associated with spectrophotommetry?

1. What is spectrophotometry and how does it work?

Spectrophotometry is a technique used to measure the amount of light absorbed or transmitted by a substance. It involves passing a beam of light through a sample and measuring the intensity of the light that passes through. The amount of light absorbed or transmitted is then used to determine the concentration of the substance in the sample.

2. What are some common sources of error in spectrophotometry?

Some common sources of error in spectrophotometry include instrument errors, sample preparation errors, and environmental factors. Instrument errors can occur due to calibration issues or malfunctioning equipment. Sample preparation errors can arise from incorrect dilution or contamination. Environmental factors, such as temperature and humidity, can also affect the accuracy of spectrophotometric measurements.

3. How can instrument errors be minimized in spectrophotometry?

To minimize instrument errors, it is important to regularly calibrate the spectrophotometer and use quality control standards to ensure accurate readings. It is also important to follow the manufacturer's instructions for proper use and maintenance of the instrument.

4. What precautions should be taken when preparing samples for spectrophotometric analysis?

When preparing samples for spectrophotometric analysis, it is important to follow the recommended methods and protocols to ensure accurate results. This may include proper dilution techniques, avoiding contamination, and using appropriate sample containers. It is also important to handle samples carefully to prevent any changes in the sample's properties.

5. How can environmental factors be controlled in spectrophotometry?

To control environmental factors in spectrophotometry, it is important to perform experiments in a controlled environment with stable temperature and humidity. If this is not possible, corrections can be made using mathematical calculations or by using reference samples with known absorbance values. It is also important to minimize any sources of external light that could interfere with the spectrophotometric measurements.

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