Calculate the activity of the chloride ion in a solution

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Discussion Overview

The discussion revolves around calculating the activity of the chloride ion (Cl-) in a mixed solution containing sodium sulfate (Na2SO4), sodium chloride (NaCl), and ferric chloride (FeCl3). Participants explore the necessary steps and formulas involved in determining the activity coefficient and the overall activity of the chloride ion.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant presents the initial calculation of ionic strength (I) as 0.0134 and seeks guidance on how to proceed with the activity calculation in a mixed solution.
  • Another participant asks for the concentration of Cl-, suggesting that it is the sum of contributions from NaCl and FeCl3, totaling 0.0026 m.
  • There is a query about the activity coefficient for an ion with a single charge in relation to the ionic strength.
  • One participant references a formula for calculating the activity coefficient, indicating a potential path forward for calculating the activity once the coefficient is known.
  • Several responses suggest a straightforward approach to the calculation, using the phrase "plug and chug," implying a direct application of the formulas without further elaboration.

Areas of Agreement / Disagreement

Participants generally agree on the method to calculate the activity of the chloride ion, but there is no consensus on the specific values for the activity coefficient or the implications of the mixed solution. The discussion remains unresolved regarding the exact steps to finalize the calculation.

Contextual Notes

Participants have not fully addressed the dependencies on definitions or assumptions regarding the activity coefficients and the ionic strength's influence on the calculations.

Who May Find This Useful

This discussion may be useful for students or practitioners in chemistry or chemical engineering who are interested in understanding the calculations related to ionic activity in mixed solutions.

il postino
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Homework Statement
Calculate the activity of the chloride ion in a solution
Relevant Equations
Ionic force
Hi everyone!
I have to calculate the activity of ##Cl^{-}##
I have a solution formed by ## Na_{2}SO_{4}## 0.0016 m + ##NaCl## 0.0014m + ##FeCl_{3}## 0.0012m

I calculated the ionic strength ##I##
##I=0.0134##

The activity of the chloride ion is ##a_{Cl^{-}}=m_{Cl}*\gamma _{Cl}##

But I don't understand how to continue when it is a mix.
Could you help me?
Thank you very much!
 
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What is the concentration of Cl-?
 
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Borek said:
What is the concentration of Cl-?

0.0014m + 0.0012m = 0,0026m

How do I continue?
Thanks Borek
 
And for a given I what is the activity coefficient for an ion with a single charge?
 
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Borek said:
And for a given I what is the activity coefficient for an ion with a single charge?

##m_{Cl}*\gamma _{Cl}##

##log(\gamma _{Cl})=-A.|Z|.\sqrt{I}##

If I calculate ##\gamma _{Cl}## can I calculate the activity without problems?
 
Plug and chug.
 
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Borek said:
And for a given I what is the activity coefficient for an ion with a single charge?

aCl−=mCl−∗γCl−
Borek said:
Plug and chug.

Muchas gracias Borek! (In Argentina jaja)
Thanks!
 

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