How to calculate surface charge

[Huastecan]

Hi to all,

I have some polymers synthesized on nanometric scale with COOH groups. I want to calculate the surface charge density, the sample was characterized by means of a conductometric titration, with a dilute solution of NaOH, the analysis gave the equivalent of NaOH to the weak acid and the conductivity in mS/cm. I know the density and the surface area of the sample, but I do not know how to calculate the surface charge of the sample, it should give a result in C/nm2 or e/nm2. How can I calculate that data? I think I must use either the Gouy-Chapman theory or the Debye-Hücker theory.

 

[gtoguy97]

Please help me out.The Gouy-Chapman theory and the Debye-Hücker theory are both useful for calculating surface charge density from an analysis of conductometric titration. The Gouy-Chapman theory deals with the distribution of ions near a charged surface, while the Debye-Hücker theory is used to calculate the surface charge density from the conductivity of a solution.In order to calculate the surface charge density using the Gouy-Chapman theory, you will need to know the surface area of the sample, the concentration of the weak acid, and the concentration of the NaOH solution. The surface charge density is then calculated using the following equation:Surface Charge Density = (2 x Concentration of Weak Acid x Surface Area) / (Concentration of NaOH x Volume of NaOH Solution)Using the Debye-Hücker theory, you will need to know the density of the sample, the conductivity of the solution, and the concentration of the NaOH solution. The surface charge density is then calculated using the following equation:Surface Charge Density = (Density x Conductivity x 10^-6) / (Concentration of NaOH x Volume of NaOH Solution)Once you have calculated the surface charge density, you can convert your units to C/nm2 or e/nm2.I hope this information helps!