How Much Acetic Acid Converts to Dimer at Equilibrium?

  • Thread starter George3
  • Start date
In summary: I figured that .005115 was the only answer that made sense. I divided that concentration by the concentration give and got the percent to be 1.7% dimer but that is incorrect. In summary, the equilibrium constant for the dimer-monomer equilibrium of acetic acid is 17 at a particular temperature. Given an initial concentration of .30mol/L at 25 C and no initial presence of dimer, the percentage of acetic acid converted to dimer can be determined by setting up an ice table and using the equilibrium constant equation. This results in a quadratic equation, from which the true value of x can be found using the quadratic formula. This value, when divided by the initial concentration, gives the percentage of
  • #1
George3
31
0
URGENT! Dimer-Monomer Percentage

Homework Statement


In the gas phase acetic acid exists as an equilibrium of monomer and dimer molecules.(The dimer consists of two molecules linked through hydrogen bonds.) The equilibrium constant for the dimer-monomer equilibrium (CH3CO2H)2 <=> 2 CH3CO2H has been determined to be 17 at a particular temperature. Assume that acetic acid is present initially at a concentration of .30mol/L at 25 C and that no dimer is present initially. What percentage of acetic acid is converted to dimer?


Homework Equations





The Attempt at a Solution


I did an ice table and found that:
I 0 .3

C x -x

E x .3-x


Then I went 17 = ((.3-x)^2)/x and got the quadratic .09 - 17.6x + x^2 after doing the
quadratic formula I found x equal to .005115 or 17.59. I figured that .005115 was the only answer that made sense. I divided that concentration by the concentration give and got the percent to be 1.7% dimer but that is incorrect. Can someone point me in the right direction?
 
Last edited:
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  • #2
Anything guys?
 
  • #3
Ratio of dimer/monomer is 17, right?

So, 17 = [x]/[0.3-x]2 and you get 0 = x2 - 17.6x + 0.09 from that?

That's not what I get.
 
  • #4
Anyway please realize it is not a pedantry to say that that equilibrium constant cannot be 17. It has to have UNITS or it's meaningless.

If you quote them they will at least tell you if you have got your equation the right way up.
 
  • #5
epenguin said:
...If you quote them they will at least tell you if you have got your equation the right way up.

Yep, I've got mine wrong side up. Sorry.

George3, this part is wrong...
...after doing the
quadratic formula I found x equal to .005115 or 17.59.
 
Last edited:

Related to How Much Acetic Acid Converts to Dimer at Equilibrium?

1. What is the meaning of dimer-monomer percentage?

The dimer-monomer percentage refers to the ratio of dimer molecules to monomer molecules in a given sample. A dimer is a molecule composed of two monomers joined together, while a monomer is a single molecule. This percentage is used to determine the level of dimerization, or the formation of dimers, in a substance.

2. How is the dimer-monomer percentage calculated?

The dimer-monomer percentage is typically calculated by dividing the number of dimer molecules by the total number of molecules in a sample, and then multiplying by 100 to get the percentage. This calculation can also be done using the weight or concentration of dimer and monomer molecules in the sample.

3. Why is the dimer-monomer percentage important in scientific research?

The dimer-monomer percentage is important in scientific research because it can provide insights into the structure and function of molecules. Changes in the dimer-monomer percentage can indicate alterations in the behavior or properties of a substance, which can be useful in understanding biological processes or developing new materials.

4. How does the dimer-monomer percentage affect the properties of a substance?

The dimer-monomer percentage can greatly impact the properties of a substance. Dimers and monomers have different sizes, shapes, and chemical properties, which can affect the overall characteristics of a substance. For example, a higher dimer-monomer percentage may result in a substance being more stable, while a lower percentage may make it more reactive.

5. Can the dimer-monomer percentage be manipulated or controlled?

Yes, the dimer-monomer percentage can be manipulated or controlled in some cases. This can be done through various methods such as changing the temperature, pH, or concentration of a substance. Scientists can also design molecules with specific properties to influence the dimer-monomer percentage. However, some substances may have a natural tendency towards a certain dimer-monomer ratio and may be more difficult to manipulate.

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