Chemical calculations theory. 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
IN CHEMICAL UNITS
-Normality, N (number of gram-equivalents of solute contained in 1 liter of dissolution):
-Molarity, M (number of moles of solute contained in 1 liter of solution):
(a = grams of solute; val = valence of solute; M = molecular mass of solute; V = volume (cm³) of
(V = volume of dissolution in liters; N = normality).
-Molality, m (moles of solute number contained in 1 kg of solvent):
(a = grams of solute; M = molecular mass of solute; m’= grams of dissolvent).
COLLEGATIVE PROPERTIES OF DISSOLUTIONS
Decrease in vapor pressure. Henry’s Law:
Po = vapor preassure of pure dissolvent.
P = vapor preassure of the dissolution
Xsol =molar fraction of solute.
Xd = molar fraction of dissolvent.
Freezing-point depression and boiling point rise. Raoult´s law.
∆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.
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