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How will these changes affect the yield (increase, reduction, no change) of the products:

  1. The product of a step doesn't get fully dried.

  2. We weighed 14 g of a reactant instead of 15 g which are required for the experiment, but we noted down 15 g.

  3. A reactant that has to be heated in order to produce another product, doesn't get enough heated.

  4. If a solid gets rinsed with only cold water, but not with acetone.

For the first one, I believe that the yield will increase, because the product won't be fully dried and the water will add mass to the product.

For the fourth one, I believe that since we are not using acetone, the product won't be dry enough, so it will also increase the yield.

For the third one, I'm not sure. But I believe if the product is not heated enough, less product will be formed, so the yield will be reduced.

For the second one, I'm also not sure.

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  • $\begingroup$ Come to think of it, real yield and apparent yield are different things, and I'm not sure which of them is referred to in the question. $\endgroup$ – Ivan Neretin Mar 27 '17 at 15:52
  • $\begingroup$ I can't answer this, because it is not referred in the question. $\endgroup$ – chemistrylove Mar 27 '17 at 15:56
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    $\begingroup$ 1,2,4 seem to be asking about apparent yield. But yes, it is unclear. $\endgroup$ – orthocresol Mar 27 '17 at 16:00
  • $\begingroup$ Is it fair to say that for the second one, there will be no change? $\endgroup$ – chemistrylove Mar 27 '17 at 16:08
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1) You are correct for question one, since the product is still wet you will weigh both your product + the water, so the true mass will be less than that weighed.

2) Your yield will be lower. Since you you less reactant (14g instead of 15g), your yield will be less than it would be if you used 15g. Since you calculate your theoretical yield using what you wrote down (15g), you will expect more product, since you assume you started with 15g of reactant, not 14g.

3) You're right again. Since the reactant is not heated sufficiently, your reaction does not go to completion, and you end up with less product.

4) I think your reasoning is ok.This is a bit unclear though. Acetone is a pretty hard solvent (meaning is dissolves many materials) so depending on what you are washing you may want to avoid acetone. Since the question is rather unclear, I suggest you provide any answer that makes sense, and is supported by reasoning. For example: I believe the yield will be greater, because water is less volatile than acetone, so it will remain in my material, and cause the my product yield to increase, unlike acetone that would evaporate quickly/easily.

You could also say that assuming the material is dried afterwards, it does not matter, but removing water is more difficult than removing acetone, so suggest washing with acetone.

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  • $\begingroup$ The acetone wash may be to remove an acetone-soluble impurity $\endgroup$ – Waylander Mar 27 '17 at 16:49
  • $\begingroup$ Good point @Waylander. I don't think there is a right or wrong answer to question 4, anything that can be supported by some reasoning should be correct since the question provides too little detail to answer objectively. $\endgroup$ – Caelan Mar 27 '17 at 21:45

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