Stoichiometry, Part II (and Percentage Yield)

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Discussion Overview

The discussion revolves around stoichiometry calculations related to the conversion of ethanol to ethanoic acid in oxidation reactions, focusing on determining expected yields and percentage yields based on given data. The scope includes mathematical reasoning and conceptual clarification regarding actual versus expected values in chemical reactions.

Discussion Character

  • Mathematical reasoning
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant presents a stoichiometry problem involving the conversion of 360g of ethanol to ethanoic acid with a percentage yield of 70%, seeking clarification on the distinction between actual and expected values.
  • The same participant calculates the expected yield based on the stoichiometric ratio and molar masses, questioning whether they confused actual and expected values.
  • Another participant confirms the calculations appear correct but prompts the original poster to consider the relationship between theoretical yield and percentage yield.
  • A second problem is posed where a chemist starts with 149.00g of ethanol and produces 180.00g of ethanoic acid, with the participant calculating the percentage yield and expressing concern about potential errors in their values or molar masses.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the calculations, particularly in distinguishing between actual and expected yields. While one participant confirms the calculations, there remains a lack of consensus on the clarity of the concepts involved.

Contextual Notes

Participants are navigating potential confusion around definitions of actual and expected yields, as well as the implications of percentage yield calculations. There are unresolved questions about the correctness of the molar masses used in calculations.

Who May Find This Useful

Students and individuals studying chemistry, particularly those focusing on stoichiometry and yield calculations in chemical reactions.

Soaring Crane
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Please (pretty please) check all of my work!

1) In an oxidation reaction, ethanol (C2H5OH) is converted to a ethanoic acid (C2H4O2) with a percentage yield of 70%. If you start the reaction with 360g of ethanol, how many grams of ethanoic acid would you expect to produce?
Stoichiometry is 1:1 between the compounds.

% yield = (actual value/expected value) *100

Given: % yield = 70

Find: expected value C2H4O2 in g

Actual value C2H4O2 in g:
360 g C2H5OH (1 mol C2H5OH / 46.068 g C2H5OH) (1 mol C2H4O2 / 1 mol C2H5OH) = 7.81454 mol C2H4O2

7.81454 mol C2H4O2 (60.052 g C2H4O2 / 1 mol C2H4O2) = 469.2785 g C2H4O2 = actual value ??

70 = (469.2785/expected) * 100
expected = 469.2785/.70 = 670 g C2H4O2 ??

Did I muddle this problem big time? I'm confused with what is the actual value and what is the expected (theoretical?) value. Did I confuse the actual for the expected?? Do you use 70% at all?


2) In an oxidation reaction, ethanol (C2H5OH) is converted to a ethanoic acid (C2H4O2). In an Experiment, a chemist starts with 149.00g of ethanol and forms 180.00g of ethanoic acid. What is the percentage yield of the reaction? Stoichiometry of the reaction is 1:1 for the mentioned compounds.


% yield = (actual value/expected value) *100

Given: 180.00 g C2H4O2 = actual value g C2H4O2 ?

Expected value of C2H4O2 :
149.00 g C2H5OH (1 mol C2H5OH / 46.068 g C2H5OH) (1 mol C2H4O2 / 1 mol C2H5OH) (60.052 g C2H4O2 / 1 mol C2H4O2) = 194.2291 g C2H4O2 ??

180 g / 194.2291 g C2H4O2 *(100) = 92.674 % ??

Gosh, I hope I didn't confuse my values or molar masses again!

Thank you. I am desperate for help. :cry:
 
Physics news on Phys.org
Anyone at all? Please? (Are my calculations correct?)

Thanks.
 
Please confirm if I did something correctly.

Thanks for your patience.
 
Your calculations look correct to me.:smile:
 
7.81454 mol C2H4O2 (60.052 g C2H4O2 / 1 mol C2H4O2) = 469.2785 g C2H4O2 = actual value ??

70 = (469.2785/expected) * 100
expected = 469.2785/.70 = 670 g C2H4O2 ??

Did I muddle this problem big time? I'm confused with what is the actual value and what is the expected (theoretical?) value. Did I confuse the actual for the expected?? Do you use 70% at all?
what you calculated here is the theoretical yield, now how is your theoretical yield less then you're actual percent yield? Think about it.

2) seems fine
 

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