# Please confirm my Activity Coefficient Calculations

• Chemistry
• Yokoko
In summary, the individual has made an error in their calculation of I and is using the incorrect equation for logγ. They have now corrected their mistake and their final value for I is 0.0666M, which aligns with the experimental value. The individual initially used c instead of √I, but now has the correct value for I.
Yokoko
Homework Statement
I've had a go at these but am unsure about the result. I thought the values would have to be closer to each other.
Relevant Equations
See picture

You have not calculated I correctly. I (not √I) = 1/2∑cz2 for ALL ions present.
Then you haven't used your calculated value for I in the equation for logγ. You used c. Why?
(Do it correctly, and it does come out close to the experimental value.)

Thanks for your answer. Again, I'm not sure if I understood this correctly.

I used c as I thought s = c for simple ions. I now took the root of √I to get I.

I assumed the C for KNO3 = 0.0050 and C for CaSO4 = s = 0.0154

This might be where I am wrong?

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No! 1/2Σcz2 is I, not √I, as I said before. (What are the units?) I = 0.0666M.

With I = 0.0666 I get an overall value of 0.41 which fits.

Thanks again!

## 1. What is an activity coefficient and why is it important in scientific calculations?

An activity coefficient is a measure of the deviation of a solution's behavior from ideal behavior. It takes into account the interactions between solute molecules and solvent molecules, and is important in calculations because it affects the accuracy of the results.

## 2. How do you calculate activity coefficients?

Activity coefficients can be calculated using various methods, such as the Debye-Hückel equation or the Pitzer equations. These equations take into account factors such as temperature, pressure, and ionic strength to determine the activity coefficient of a solution.

## 3. Can activity coefficients be negative?

Yes, activity coefficients can be negative. This occurs when the interactions between solute and solvent molecules are stronger than expected, resulting in a lower activity than predicted by ideal behavior.

## 4. How do activity coefficients affect the accuracy of calculations?

Activity coefficients can significantly affect the accuracy of calculations, especially in non-ideal solutions. If activity coefficients are not taken into account, the calculated values may be significantly different from the actual values, leading to inaccurate results.

## 5. Are there any limitations to using activity coefficients in calculations?

Yes, there are limitations to using activity coefficients in calculations. Activity coefficients are only accurate within a certain range of conditions, such as temperature and concentration. Additionally, they may not accurately predict the behavior of highly concentrated solutions or solutions with complex chemical interactions.

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