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Calculate the Density of a solution of Formic acid in Water

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The density of a Formic acid is a difficult problem, due to association. We can adjust the interaction between molecules (the dread kij factors) to account for this association

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Setup

Note: this is the path to the installed EOS packages

Last Run on:

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Formic Acid Solution Density--Finding minimum errors using (an) adjustable Kij value(s)

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Formic Acid (HCOOH) represents a very difficult calculation, since it is found mostly in dimers. Hence, it represents a 'worst case' scenario for EOS of associating species. We handle it using interaction coefficients in the most accurate of the models, the Aasberg-Petersen*

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Functions

Lden is the density of the mixture z at temperature t, atomospheric pressure (.98 bar).

Next,the dtermining the sqr.error.LiquidDensityError takes a range of t's,a range of z's,and a list of real data,which should be of the form:

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Data

Formic acid solution density {concentration__List:{__temperature}}, where concentration is mole percent HCOOH, temperature is 0, 15, 20, 30 ºC

Reform data and sample at every 0.05 change in mole fraction

NOw, Examine graph of density of 4 temperatures

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Using Equations of State to make Predictions

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No kij adjustments

Plot the predictions along with the experimental

Store the MS error

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Adapt the models to include one kij Adjustment

The following is a table of errors as a function of the k11 value

Now, replicate the data using the above 'best' k11 value for the water-formic acid mix

Though more kij adjustments slightly improve the guess, they do not SIGNIFICANTLY improve the guess (as shown below)

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Two kij Adjustments

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Three kij Adjustments

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four kij Adjustments

Converted by *Mathematica*
May 6, 2002