胶体（colloid）.docVIP

胶体（colloid） Fifth chapter colloid Home page Problem analysis Student self test questions Student answer Chapter after Exercises answer Problem analysis [TOP] Example 5-1 why is the sol a thermodynamically unstable system while the sol is kinetically stable? The solution sol is a polydisperse system highly dispersed, highly dispersed sol makes a large specific surface, so the surface energy, they automatically accumulate into large particles and reduce the surface area of the trend, namely the coalescence instability. It is a thermodynamic unstable system. On the other hand, sol particles exist severe Brown motion, can make itself less prone to settlement, is a stable factor at the same time with the same sol; charged colloidal particles exist between electrostatic repulsion, and hydration of micelles of double layer membrane is like a layer of elastic film, rubber particles collide with variable block big. Therefore, the sol has dynamic stability. The colloidal particles of the 5-2 silicic acid sol are polymerized by silicic acid. The nuclei are aggregates of SiO2 molecules whose surface H2SiO3 molecules can dissociate into SiO32- and H+. H2SiO3 2H+ +SiO32- H+ ions diffuse into the medium. Write the structure of silica gel, point out the double layer structure of silica gel and the electric property of colloid. Structure formula of silica gel [(SiO2) m? NSiO32-? 2 (Nx) H+] 2xH+ 2x? Glue surface of the core of SiO32- ion and H+ ion adsorption layer composed of negatively charged H+ ions, the remaining component diffusion layer, diffusion layer formed by adsorption layer with negative charge and H+ ions with positive charge of electricity instead of diffuse double layer. Colloidal particles carry a negative charge. Example 5-3 what is surfactant? The reasons for reducing the surface tension of the solution are explained in terms of its structural characteristics. The addition of certain solutes in water reduces the surface tension of the water, a substance that lowers