Chapter_12_Part_1 - Chapter 12: Solutions Part 1 Solution...

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Unformatted text preview: Chapter 12: Solutions Part 1 Solution Formation 1. Types of Solutions A solution is a homogenous mixture. The majority component is the solvent; the minority component is the solute. Solute particles are small: small molecules or ions. When the particles are relatively large, the mixture is called a colloid. The components are the phases: dispersed and ?. Solids that dissolve in a liquid are soluble in that liquid (solvent). The opposite is insoluble. Fluids that dissolve in each other are miscible. The opposite is immiscible. (See the figure to the right. A solution may be made of a solid, liquid, or gas dissolved in a solid, liquid, or gas. 2. Solubility and the Solution Process a. Solubility; Saturated Solutions i. saturated: ii. iii. b. CHM 1220/1225 unsaturated: supersaturated: Factors Explaining Solubility Two factors are involved: • natural tendency to mixing (disorder or increasing entropy) • forces of attraction between/among solute units Chapter 12 Part 1 1 of 3 between/among solvent units between solute units and solvent units c. Molecular Solutions General rule: like dissolves like Polar solutes dissolve in polar solvents (like water) • the dipole–dipole forces between solute H units and between solvent units are + d O dreplaced by dipole–dipole forces between H solute and solvent units d- polar + solute d O d+ H d- H Nonpolar solutes dissolve in nonpolar solvents d. Ionic Solutions Solubility varies widely Force of attraction between solute units: lattice energy • increases with higher charge ions • increases with smaller size ions Force of attraction between solvent (water) units: London, dipole–dipole and hydrogen bonding Force of attraction between solute units and solvent units: hydration energy • increases with higher charge ions • increases with smaller size ions 3. Effects of Temperature and Pressure on Solubility a. Temperature Change For gases: • solubility decreases as temperature increases For solids (see graph above): CHM 1220/1225 Chapter 12 Part 1 2 of 3 • the impact of temperature on solubility varies • the impact of temperature depends on the heat of solution, DHsoln ––> if the solution process is endothermic, increasing temperature increases solubility ––> if the solution process is exothermic, increasing temperature decreases solubility b. Pressure Change For gases: • solubility increases as pressure increases c. Henry’s Law: Relating Pressure to the Solubility of a Gas in a Liquid Henry’s Law: Gas solubility is directly proportional to pressure. S = kHP Variations: S1 P1 = S2 P2 S1 P1 P1 S1 CHM 1220/1225 S2 =P 2 = P2 S2 Chapter 12 Part 1 3 of 3 ...
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