Dissolutions

Dissolutions are homogeneous mixtures resulting from the interposition of atoms, molecules or ions from two or more substances, called components, which are involved in varying proportions.

WAYS TO EXPRESS THE CONCENTRATION OF DISSOLUTIONS

IN PHYSICAL UNITS

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IN CHEMICAL UNITS

-Normality, N (number of gram-equivalents of solute contained in 1 liter of dissolution):

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-Molarity, M (number of moles of solute contained in 1 liter of solution):

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(a = grams of solute; val = valence of solute; M = molecular mass of solute; V = volume (cm³) of

dissolution).

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(V = volume of dissolution in liters; N = normality).

-Molality, m (moles of solute number contained in 1 kg of solvent):

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(a = grams of solute; M = molecular mass of solute; m’= grams of dissolvent).

COLLEGATIVE PROPERTIES OF DISSOLUTIONS

Decrease in vapor pressure. Henry’s Law:

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P_o = vapor preassure of pure dissolvent.

P = vapor preassure of the dissolution

X_sol =molar fraction of solute.

X_d = molar fraction of dissolvent.

Freezing-point depression and boiling point rise. Raoult´s law.

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∆t = increase the ebullioscopic point or decline the cryoscopic point.

K = molal constant boiling or freezing

m = molality of the dissolution

a = g of solute by kg of dissolvent.

M = molecular mass of solute.

You can download the App BioProfe READER to practice this theory with self-corrected exercises.