Water o c ho c ho c o vitaminvitamin b2 c ho h h c ch

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Unformatted text preview: Apply the like-dissolves-like rule to determine if like-dissolveseach vitamin is water soluble. water O C HO C HO C O VitaminVitamin-B2 C HO H H C CH 2 OH VitaminVitamin-C CH3 C H VitaminVitamin-E H C H HO C C CH C C C CH2 H 3C C O CH3 CH3 CH2 CH2 CH CH3 CH3 CH2 CH2 2 CH2 CH CH2 CH2 2 CH2 CH 2 CH3 CH3 The stronger the attraction between solute and solvent molecules, the higher the solubility. Water Water Solubility of Solids Solubility: Solute concentration in a saturated solution. Water solubility of solids increases with temperature, but increases pressure pressure has little effect. Why? Higher T Higher kinetic Higher energy Molecules energy of Molecules • Break away from a solid. • Mix with water molecules. Pressure cannot change the definite volume of solids / liquids. Most solids How to get a pure compound from a mixture on the basis of their different solubilities? Suppose you have a sample of 90 g KNO KNO3 contaminated with 10 g NaCl, NaCl, how how do you purify the sample? Fractional crystallization: 1. 1. Dissolve sample in 100 mL of water at 600C 2. Cool solution to 00C 3. All NaCl will stay in solution (s = 34.2g/100g) 4. 78 g of PURE KNO3 will precipitate (90 g – 12 g) = 78 g (s = 12 g/100g). Water Solubility of Gases Water Water solubility of gases decreases with temperature, but increases increases greatly with pressure. Why? Higher T Higher kinetic energy Higher of Molecules For most of gases Pressure forces gas molecules to enter the solution G as N2 S o lu b ility ( M ) 0 .6 9 × 1 0 -3 in w a ter CO O2 Ar Kr 1 .0 4 × 1 0 -3 1 .3 8 × 1 0 -3 1 .5 0 × 1 0 -3 2 .7 9 × 1 0 -3 Pressure & Solubility of Gases Henry’s Henry’s Law Gas solubility in a liquid is directly proportional to the partial pressure of gas above the liquid when temperature is held constant. S g a s = k ⋅ Pg a s Sgas: gas concentration in a liquid; Pgas: Partial pressure of gas; k : Henry’s constant at certain T. Exercise Exercise: Estimate the concentration of O2 in Siyuan lake based on the data of solubility of gas...
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This document was uploaded on 02/26/2014.

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