The Surfactants and Phase Components

Using the viscosity of pure water, estimate the creaming rate for a fat droplet of density 0.925 g cm and diameter 5 x 10 m. 

Tetradecane was emulsified at 25°C in two 0.5% (w/w) surfactant solutions (a) Ci2H25-(OCH2CH2)sOH (b) Ci2H2s0S03Na. What class of emulsion would you expect in each case What would you expect to be the natures of the two emulsions when heated to 50°C  

One of the processes by which an emulsion, like a foam, destroys itself is by Ostwald ripening the diffusion of liquid from small to large droplets. Calculate the time required for a benzene droplet to disappear when it is positioned near much larger droplets at a distance comparable to its radius. Assume droplet radii of 100 and 1000 nm. The solubility of benzene in water may be taken as 0.2% (vol/vol) the diffusion constant of benzene in water D = 10 cm s the interfacial tension of water-benzene s = 25 mN m and the molar volume of benzene Vm = 100 cm.  

Calculate (to the nearest whole number) the maximum possible value for the dispersed phase fraction, 4 , in an emulsion consisting of uniform spherical particles. 

A simple geometric theory for the stabilization of emulsions is that of the oriented wedge, in which the adsorbed surfactant molecules are assumed to form a uniform structure of wedges around the emulsion droplet. If an emulsion of 1000-nm-diameter droplets is stabilized by a surfactant whose head group occupies a surface area of 0.45 nm, what must be the cross-sectional area of the hydrophobic tail for maximum effectiveness  

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