Physical Chemistry of Foods
is compensated by the difference in height of, hence in gravitational pressure in, both compartments. Incidentally, this implies ...
can also be written asPV&nRT; the equation is thus of the same type as Eq. (2.12). Thevalidityof the quantitative relations give ...
2.2.5 Deviations from Ideality In foods, we often have situations in which concentrations are markedly different from activities ...
ð 4 = 3 Þpr^3 , but another molecule cannot come closer to it than a distance 2r (taking the position of the molecules to be at ...
deviations from ideality at high concentration, especially if the solute molecules are large. The effect of concentration is oft ...
colligative properties. From the results depicted in Figure 2.3, it can be derived that for sucrose solutions a second virial co ...
may be expected. For very concentrated systems, as in partly dried foods, very large deviations between concentration and activi ...
soaps and other small-molecule surfactants, which form micelles, i.e., roughly spherical aggregates in which the hydrophobic tai ...
FIGURE2.8 The effect of micelle formation on some solution properties. (a) Schematic picture of micelle formation. (b) Osmotic p ...
may still be available as a reactant, although it will react only sluggishly. But if no micelles were present, a very apolar ‘‘s ...
Question 2 An oil-in-water emulsion, with an oil volume fractionðjÞof 0.2, contains a certain fatty acid (HAc); total concentrat ...
Note A certain amount of the fatty acid may adsorb on the oil–water interface. If the oil droplets are small, this may be an app ...
ion activity coefficientof NaCl as g+ðNaClÞ:½gþðNaþÞ?gðClÞ^1 =^2 ð 2 : 22 Þ Note that the subscripts to the activity coeffici ...
dissociation is greater. Figure 2.9b gives a titration curve for citric acid; here the degree of neutralization rather than diss ...
KDis now in mol^2 ?L^2 rather than moles per liter. Further, g+ðCaCl 2 Þ¼½gþðCa^2 þÞ?g^2 ðClÞ^1 =^3 or, more generally, for ...
shielding the charge of the ion. Entropy is highest if all ions are completely distributed at random, but the attractive electri ...
causes the temperature influence to be fairly small.) For water at 20 8 C, e¼80, and the equation becomes g+&expð 1 : 17 jj ...
small differences are found for most inorganic ions, except for the hydrogen ion, which has a higher activity coefficient than p ...
and it is seen that especially for valences higher than 1 the effect is great. In calculating the above figures, one has to know ...
Although the results may be only approximate, they are very much better than those obtained when ignoring association, or even w ...
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