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Chapter 17

CHM 111 Chapter Notes - Chapter 17: Kilogram, Ideal Solution, Molality

Course Code
CHM 111
Acevedo Orlando

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Solution Composition
A. Molarity: the number of moles of solute per liter of solution
B. Mass percent: percent solution by mass in the solution (grams of solute/grams of
C. Mole Fraction (x): the ratio of the number of moles of a given component to the total
number of moles of solution
D. Molality (m): the number of moles of solute per kilogram of solvent (moles of
solute/kilograms of solvent)
Factors Affecting Solubility
A. Structure Effects
a. Solubility is favored if the solute and solvent have similar polarities. Since the
molecular structure determines polarity, there should be a definite connection
between structure and solubility
b. Fat-Soluble:
i. Composed mostly of carbon and hydrogen atoms with similar
electronegativity and virtually nonpolar
ii. Soluble in nonpolar materials but not soluble in polar solvents
iii. Hydrophobic
c. Water-soluble
i. Many polar bonds, making the molecule polar and water-soluble
ii. Hydrophilic
B. Pressure Effects
a. Gas solubility increases with pressure
i. If pressure is suddenly increased, the number of gas molecules per unit
volume increases; thus the gas enters the solution at a higher rate than it
ii. As the concentration of dissolved gas increases, the rate of escape of the
gas also increases
b. Relationship between pressure and concentration of dissolved gas is given by
Henry’s Law: P=kHx
c. Henry’s Law: The amount of gas dissolved in a solution is directly proportional to
the pressure of the gas above the solution
i. Most accurate for gases that do no dissociate
C. Temperature Effects
a. The dissolving of a solid occurs more rapidly at higher temperatures, but the
amount of solid that can be dissolved may increase or decrease with increasing
b. Behaviors of gases
i. Decreasing water solubility with increased temperature
1. Also responsible for formation of boiler scale
The Vapor Pressure of Solutions
A. If the vapor pressure of the pure solvent is greater than that of the solution
a. Pressure of vapor necessary to achieve equilibrium with the pure solvent is greater
than that required to reach equilibrium with the solution
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