Solving Yield Gone Wrong in Chemistry Lab

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In summary, the conversation discusses the issue of obtaining accurate yield measurements in a chemistry lab experiment. The questioner forgot to measure the mass of the filter paper used, leading to difficulty in calculating the yield. Solutions are suggested, such as using statistics to estimate the error range, and washing the filter paper with solvent to remove any residual substances. The conversation also includes tips for future experiments, such as leaving spaces in the lab notes to collect necessary data.
  • #1
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Yield gone wrong!

Hi, I just have a question about some practical things in a chemistry lab and errors.
:uhh:
We carried out a recrystallization experiment of benzoic acid and napthalene :zzz: last week and during one of the steps where i was supposed to transfer my pure sample of benzoic acid from a 5mm calibrated test tube onto a filter paper and dry in an electric oven to weigh the mass obtained and calculate the %yield (all of the apparatus used is for macroscale organic chemistry experiments...oh i forgot to mention that this is an organic chemistry experiment, unless its obvious :tongue2: ) i forgot to measure the mass of the filter paper itself and it seems that the filter papers have quite big differences in mass...my friend recorded a filter paper mass of 0.766g
so now all i have is the weight of the pure benzoic acid and filter paper which is 0.879g...so i can't find the mass of pure benzoic acid now since i don't know the weight of the filter paper and hence can't calculate the yeild.
my question is if there is any method to obtain the mass of my filter paper? is it a good idea to measure the mass of a few filter papers and take the average of them and use that value?

fyi i started with 0.103g of impure benzoic acid :shy:

thanks :)
 
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  • #2
If the weights vary quite a bit you could use some simple statistics (st. dev or something) to give a good idea to the reader what range of error you might have. It should still be mentioned in your report/write-up that the filter mass wasn't taken originally and that an average mass of a few filters was substituted.
 
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  • #3
remove the benzoic acid from the dry filter paper and rinse with solvent to completely remove it. Use acetone. dry filter paper and weigh.

Next time write out your lab leaving spaces (underlined) for data you need to collect. I know it is a pain, but it works. No need to do this once you become familiar with routine tasks.
 
  • #4
thanks for the advice guys :) i'll keep it in mind


chemisttree: remove the benzoic acid from the dry filter paper and rinse with solvent to completely remove it. Use acetone. dry filter paper and weigh.

i'll definitely keep that in mind

(sorry i don't know how to use all the exact functions in here yet)
 
  • #5
If you are going to be washing the filter paper with solvent to remove the benzoic acid it would be a good idea to do the same procedure to a unused filter. This would let you know if the solvent is extracting anything out of the filter (which shouldn't happen, but its still a good thing to check)
 
  • #6
really good point dmoravec thanks :)
 

1. What is "yield" in chemistry?

Yield in chemistry refers to the amount of product obtained from a chemical reaction, usually measured in grams or moles.

2. Why might a yield go wrong in a chemistry lab?

There are several factors that can contribute to a poor yield in a chemistry lab, including incorrect measurements, impure reactants, or incomplete reactions.

3. How can I prevent a yield from going wrong?

To prevent a yield from going wrong, it is important to carefully measure and mix reactants, use pure chemicals, and ensure all reactions are carried out under the correct conditions.

4. What should I do if my yield does go wrong?

If your yield does go wrong, it is important to troubleshoot the experiment to identify the source of the error. This may involve repeating the experiment, adjusting reaction conditions, or using different reactants.

5. Is a low yield always a bad thing?

No, a low yield does not necessarily mean a failed experiment. It may simply indicate that the reaction is not very efficient or that there are other factors affecting the yield. It is important to consider the overall goal of the experiment and the expected yield before determining the success of the reaction.

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