lec4_2011

lec4_2011 - Solution that contains more than one types of...

This preview shows pages 1–5. Sign up to view the full content.

The ionic strength of the solution equals the sum of the ionic strength of each individual compound. Example: Calculate the ionic strength of a solution that contains 0.050 mol kg -1 K 3 [Fe(CN) 6 ](aq), 0.040 mol kg -1 NaCl(aq), and 0.03 mol kg -1 Ce(SO 4 ) 2 (aq). Solution: I(K 3 [Fe(CN) 6 ]) = ½( 1 2 *(0.05*3) + (3) 2 *0.05 + (-1) 2 *(0.05*6)) = 0.45; I(NaCl) = ½(1 2 *0.04 + (-1) 2 *0.04) = 0.04; I(Ce(SO 4 ) 2 ) = ½(4 2 *0.03 + (-2) 2 *(2*0.03)) =0.36; So, I = I(K 3 (Fe(CN) 6 ]) + I(NaCl) + I(Ce(SO 4 ) 2 ) = 0.45 + 0.04 + 0.36 = 0.85 Solution that contains more than one types of electrolytes

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Calculating the mean activity coefficient Example : Calculate the ionic strength and the mean activity coefficient of 2.0 mmol kg -1 Ca(NO 3 ) 2 at 25 o C. Solution: ionic strength I I = ½(2 2 *0.002 + (-1) 2 *(2*0.002)) = 3*0.002 = 0.006; plug I into the Debye-Huckel limiting equation log(γ ± ) = - |2*1|*A*(0.006) 1/2 ; = - 2*0.509*0.0775; = -0.0789; γ ± = 0.834;
Experimental test of the Debye-Hückel limiting law

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Accuracy of the Debye-Hückel limiting law Example : The mean activity coefficient in a 0.100 mol kg -1 MnCl 2 (aq) solution is 0.47 at 25 o C. What is the percentage error in the value predicted by the Debye-Huckel limiting law? Solution: First, calculate the ionic strength I = ½(2 2 *0.1 + 1 2 *(2*0.1)) = 0.3 to calculate the mean activity coefficient.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern