11.1 The Dissolution Process

11.1 The Dissolution Process

by Luis Bello

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​Previous Class

​Phase Transitions

Phase Diagrams

Multiple Choice

**An ice cube feels cold when we hold it. Which of the following best explains why?

• Heat moves from our hands into the ice cube.

• Cold moves from our hands into the ice cube.

• Heat moves from the ice cube into our hands.

• Cold moves from the ice cube into our hands.

Multiple Choice

What line segment represents only the solid state? (Diagram F)

• A-B

• B-C

• C-D

• D-E

Multiple Choice

Between which points is the temperature of the substance remaining constant? (Diagram F)

• A-B only.

• A-B, C-D, E-F

• B-C only.

• B-C, D-E

Multiple Choice

True or false: melting and freezing occur at the same temperature!

• True

• False

• I don't know

Multiple Choice

A substance's heating curve is shown in the graph. What is its boiling point? (Diagram B)

• 100 C

• 60 C

• 80 C

• 20 C

Multiple Choice

Is the substance gaining or losing energy? (Diagram D)

• Gaining

• Losing

Multiple Choice

What will occur when the substance changes from 1 atm to 30 at a constant temperature of -15^oC? (Diagram A)

• condensation

• deposition

• melting

• sublimation

Multiple Choice

What is point A? (Diagram C)

• triple point

• critical point

• equilibrium point

• normal melting point

Multiple Choice

What is the normal boiling point of this substance? (Diagram C)

• 150 °C

• 100 °C

• -50 °C

• 0 °C

Multiple Choice

What is the normal melting point of this substance? (Diagram C)

• 150 °C

• 100 °C

• -50 °C

• 0 °C

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​​11.2 Electrolytes

By the end of this section, you will be able to:

• Define and give examples of electrolytes

• Distinguish between the physical and chemical changes that accompany dissolution of ionic and covalent electrolytes

• Relate electrolyte strength to solute-solvent attractive forces

​Solutions of Gases in Liquids

​Henry’s law

​For many gaseous solutes, the relation between solubility, C_g, and partial pressure, P_g, is a proportional one:

Cg=kPg

where k is a proportionality constant that depends on the identities of the gaseous solute and solvent, and on the solution temperature. This is a mathematical statement of Henry’s law: The quantity of an ideal gas that dissolves in a definite volume of liquid is directly proportional to the pressure of the gas.

​Application of Henry’s Law

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At 20 °C, the concentration of dissolved oxygen in water exposed to gaseous oxygen at a partial pressure of 101.3 kPa is 1.38 × 10⁻³ mol L⁻¹. Use Henry’s law to determine the solubility of oxygen when its partial pressure is 20.7 kPa, the approximate pressure of oxygen in earth’s atmosphere.

​Solution

​Solutions of Liquids in Liquids

​Some liquids may be mixed in any proportions to yield solutions; in other words, they have infinite mutual solubility and are said to be miscible.

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Ethanol, sulfuric acid, and ethylene glycol (popular for use as antifreeze, pictured in Figure 11.13) are examples of liquids that are completely miscible with water.

​Two liquids that do not mix to an appreciable extent are called immiscible

​Separate layers are formed when immiscible liquids are poured into the same container. Gasoline, oil, benzene, carbon tetrachloride, some paints, and many other nonpolar liquids are immiscible with water.

​Solutions of Solids in Liquids

​The dependence of solubility on temperature for a number of solids in water is shown by the solubility curves in Figure 11.16. Reviewing these data indicates a general trend of increasing solubility with temperature, although there are exceptions, as illustrated by the ionic compound cerium sulfate.