Control of colloid chemistry, Option 2

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Uploaded: 20.09.2012
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Question №2

Please rate the place of colloid chemistry in the food technology.

Question №25

Changes in surface tension during adsorption.

Question №47.

Brownian motion and its quantitative characteristics.

Question №79

Adsorption decrease in strength. The use of surfactants to reduce the strength (the Rehbinder effect).

Question №103

What are the direct and inverse emulsion? How is the treatment phase of the emulsion? How to determine the type of emulsion experiments?

Question №122

The chemical nature and structure of macromolecules.

Problem №2

Human red blood cells are disc-shaped with a diameter of 7.5 mm and a thickness of 1.6 microns. Calculate the specific surface area and the radius of an equivalent sphere having 1) the same volume, 2) the same surface area. Take the density of matter corpuscles 1.00 g / cm3.

Task №102.

At 25 ° C the surface tension of water solutions of propionic acid depends on its molality as follows:

with mol / kg H2O 0.263 0.837 1.466 3.741

MN / m 60.0 49.0 44.0 36.0

Plot depending lnc and determine from it the excess surface concentration. Locate the area per one molecule of acid.

Task №202.

The whole cow´s milk sredneobёmny fat droplet diameter of from 2.9 to 4.4 microns depending on individual circumstances. Other characteristics are more constant at 20 ° C, the density of fat 0.920 g / cm3, the density of the dispersion medium (skimmed milk) 1.034 g / cm3, viscosity 1.60 mPa?s.

Assume, whole milk fat droplet diameter is 3 micrometers at 20 ° C in a rectangular cardboard "package" 15 cm. At the initial time drops uniformly distributed in height. How much time will emerge on the surface of the milk fat 50%, if all the drops have the same diameter? (Note that in these conditions, the ascent of 50% of fat is equal to ascent time with a drop of half the height of the package).

Task №302.

Fats and lipids are absorbed by the body due to the multi-step process of dispersion, which in the latter stages of the important role played by the ability of bile salts to form mixed micelles. Micelles of one of the components of such salts, deoxycholic acid sodium salt (molar mass 415.55 g / mol) were studied by osmometry 25?S with an aqueous NaCl solution with the following results:

Cm, kg / m3 4.0 8.0 12.0 16.0

KPa (solution 0.03 mol / l NaCl) 1,47 3,18 5,15 7,32

where Cm excess concentration of micelles in solution chamber (relative to the solvent chamber). Calculated from these data micelles molar mass and the number of molecules in a micelle (aggregation number).

Task №402

Assume dispersion medium slurry is lithium perchlorate LiClO4 0,1 mmol / dm3 in formamide at 25 ° C (r = 109,5). Calculate the thickness of the ion atmosphere 1 in this environment. Which equation should be used to calculate the results of electrophoresis -potential, if the radius of the particles was 6 nm?

Task №502

The table below shows the results of measurements of the viscosity of the cream with skim (non-fat) milk as a function of the concentration of fat in the 64?S:

s, wt.% 27.4 18.3 9.1 6.1 0

* G / cm3 0.9766 0.9889 1.002 1.008 1.015

, Cps 1,952 1,281 0.872 0.777 0.644

* Density of the emulsion; fat cream density 0.8887 g / cm3.

Build on these data a graph of the viscosity of the volume fraction of the fat and determine the intrinsic viscosity. Is it equal to the theoretical ratio of the Einstein equation for suspensions?

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