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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: jredifer on July 30, 2005, 09:47:33 PM

Title: Limiting Reactant and Balancing Chemical Equation problem
Post by: jredifer on July 30, 2005, 09:47:33 PM
Problem:
     Identify the limiting reactant and how much aspirin (C9H8O4) can be produced when 52.3g of salicylic acid (C8H6O3) react with 25.0g of acetic acid (CH3CO2H): C8H6O3 + CH3CO2H ----> C9H8O4 + H2O.

I have balanced this equation thus: C8H6O3 + 5CH3CO2H -----> 2C9H8O4 + 5H2O;
and computed the limiting reactant to be acetic acid (CH3CO2H) with 25.0g of acetic acid yielding 30.0g of aspirin (C9H8O4).

     The answer the book provides is: Limiting reactant = salicylic acid; theoretical yield = 62.8g aspirin.

     I have checked my calculations several times, and unless the answer the book provides is wrong, then I must have balanced the chemical equation incorrectly.  Thanks in advance for any light you may be able to shed on this.
Title: Re:Limiting Reactant and Balancing Chemical Equation problem
Post by: Yggdrasil on July 30, 2005, 11:23:04 PM
Are you sure the chemical forumlas are correct?  I think the chemical formula for salicylic acid should be C7H6O3.
Title: Re:Limiting Reactant and Balancing Chemical Equation problem
Post by: Borek on July 31, 2005, 04:36:43 AM
Check out the reaction equation - it should go 1:1. Probably that's what you will arrive at after after correcting formula.
Title: Re:Limiting Reactant and Balancing Chemical Equation problem
Post by: xiankai on July 31, 2005, 05:03:27 AM
u dont have to balance the reaction; it is done for you. convert given data to moles to find limiting regeant.
Title: Re:Limiting Reactant and Balancing Chemical Equation problem
Post by: jredifer on July 31, 2005, 12:00:51 PM
Quote from: Yggdrasil on July 30, 2005, 11:23:04 PM
Are you sure the chemical forumlas are correct?  I think the chemical formula for salicylic acid should be C7H6O3.

The book does list C8H6O3 as the formula for salicylic acid, if I change the formula to C7H6O3 it balances the equation (I think), however I then arrive at limiting reactant = salicylic acid producing 68.2g of aspirin; not the answer provided of 62.8g.

Quote from: xiankai on July 31, 2005, 05:03:27 AM
u dont have to balance the reaction; it is done for you. convert given data to moles to find limiting regeant.

As far as I know for the reaction equation to be balanced, there should be the same number of each atoms on each side,given the equation C8H6O3 + CH3CO2H ----> C9H8O4 + H2O, I count 10 C atoms, 10 H atoms and 5 O atoms on the left side, and 9 C atoms, 10 H atoms and 5 O atoms on the right side.  Is my understanding of this concept incorrect?

Quote from: Borek on July 31, 2005, 04:36:43 AM
Check out the reaction equation - it should go 1:1. Probably that's what you will arrive at after after correcting formula.

If the ratio of Salicylic acid to Aspirin stays at 1:1 I will come up with 52.3g of salicylic acid producing 62.8g of aspirin, just as the book says, however I can find no way to balance this equation while keeping the ratio of salicylic acid to aspirin at 1:1.

Thanks again I appreciate all your insight into this problem.





Title: Re:Limiting Reactant and Balancing Chemical Equation problem
Post by: sdekivit on July 31, 2005, 12:11:48 PM
Quote from: jredifer on July 30, 2005, 09:47:33 PM
Problem:
     Identify the limiting reactant and how much aspirin (C9H8O4) can be produced when 52.3g of salicylic acid (C8H6O3) react with 25.0g of acetic acid (CH3CO2H): C8H6O3 + CH3CO2H ----> C9H8O4 + H2O.

I have balanced this equation thus: C8H6O3 + 5CH3CO2H -----> 2C9H8O4 + 5H2O;
and computed the limiting reactant to be acetic acid (CH3CO2H) with 25.0g of acetic acid yielding 30.0g of aspirin (C9H8O4).

     The answer the book provides is: Limiting reactant = salicylic acid; theoretical yield = 62.8g aspirin.

     I have checked my calculations several times, and unless the answer the book provides is wrong, then I must have balanced the chemical equation incorrectly.  Thanks in advance for any light you may be able to shed on this.

you did it all correctly. I think the book is wrong. The formula of salicylic acid is C7H6O3 and then you'll find that salicylic acid is the limiting reagent and the theoretical yield of aspirin would be 68,2 g.

You made the reaction perfectly balanced if salicylic acid would be C8H6O3 :)



Title: Re:Limiting Reactant and Balancing Chemical Equation problem
Post by: Borek on July 31, 2005, 12:20:57 PM
Quote from: jredifer on July 31, 2005, 12:00:51 PM
The book does list C8H6O3 as the formula for salicylic acid

So it seems the book is wrong, check our chemical structures section (link on the left).

If you are not familiar with organic structures please remember, that every node is a carbon and if it seems to be bivalent or trivalent it is bonded with hydrogens (omitted for clarity of the structure).