Unformatted text preview: rger the ENERGY OF HYDRATION The Better the Solute Disso lves in Water IONDIPOLE FORCES are inversely proportional to the size of the ion. The smaller the ion The stronger the IONDIPOLE forces The larger the ENERGY OF HYDRATION 7 The Better the Solute Disso lves in Water Chemistry 101 II. Chapter 12 IONION FORCES OF ATTRACTION
· These are attractions between cations (+) and anions () in the crystal lattice.
· Separation of Ions from crystal lattice requires energy and is an endothermic process
· LATTICE ENERGY is the energy required to separate the ions fro m the crystal lattice. NOTE: 1. IONION FORCES work against the solution process. The stronger the IONION forces 2. The larger the Energy required to separate the ions The less likely that solute will disso lve in water IONION FORCES : Ø are inversely proportional to the size of the ions. Ø are direct ly proportional to the charges of the ions CONCLUSIONS: 1. A so lute is likely to disso lve in water if: HYDRATION ENERGY LATTICE ENERGY 2. A so lute is not likely to disso lve in water if: HYDRATION ENERGY LATTICE ENERGY 3. The solution process is favored by: Ø any decrease in LATTICE ENERGY Ø any increase in HYDRATION ENERGY 4. Two main factors affect the LATTICE ENERGY and the HYDRATION ENERGY A) Size of the Ions: inversely proportional to both B) Charge of the ions: directly proportional to the LATTICE ENERGY 8 Chemistry 101 Chapter 12 FACTORS AFFECTING SOLUBILITY I. TEMPERATURE 1. Solubilit y o f Ionic Substances in Water KNO3 Solubility (g solute/100 g water) CuSO4 NaCl Ce2(SeO4)3 o Temperature ( C) · For the majorit y of Ionic Salts, the Solubilit y increases wit h temperature (the warmer the water, the better they disso lve). Except ions: Ce2(SeO4)3 , Ca(OH)2, CaSO4 2. Solubilit y o f Gases in Water
· The Solubilit y o f gases decreases wit h increasing temperature (the colder the water, the better the gases dissolve). Examples are: Ø soda water keeps its carbonat ion (CO2 gas) better at low temperatures (at room temperature they go “flat” faster) Ø cold...
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