Environmental Engineering Reference
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Salt concentration, g/L
Figure 4.109 Osmotic suction versus salt concentration in grams per liter of NaCl.
the linear increase in osmotic suction with the molarity of a
salt solution of NaCl ranging from 0.001M to 100 M. The
effect of temperature is small and only the computed results
corresponding to 20 C are shown. The osmotic suction is
about 4870 kPa at 1 M.
The molecular weight of a salt corresponds to the weight
of Avagadro's number of atoms (i.e., 6 . 022
weight of 35.453 g. Added together, the atomic weight of
NaCl molecules is 58.443 g. One mole is equal to Ava-
gadro's number of atoms. Therefore, the molecular weight
is the weight of 1mol of molecules. Or stated another way,
the atomis weight of 1mol of NaCl is 58.443 g.
Figure 4.109 shows osmotic suction plotted versus the salt
concentration of NaCl in grams per liter. A salt solution of
10 g/L gives an osmotic suction of about 810 kPa. Compar-
ing Figs. 4.108 and 4.109 shows that 58.4 g/L of NaCl is
equal to a 1M solution of NaCl.
10 23 ). Let us
consider the molecular weight of NaCl. Sodium, Na, has an
atomic number of 11 and an atomic weight of 22.990 g.
Chlorine, Cl, has an atomic number of 17 and an atomic
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