Friday, January 29th, 2010

Friday, January 29th, 2010 - Hydration of Na+ : Steps 2+3 :...

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Friday, January 29, 2010 Delta H (c.l.) positive or negative. Exothermic : Delta H is negative Chapter 13.5 : crystal lattice energy. Na+ + Cl- - NaCl (s) + heat Dissolve the salt Expand solute + solvent (Delta H2) | | | | Expand solute + solvent | (+Delta H1) | | | | Solute (salt) + solvent| | | (Delta H solution) | | | Solution Because it was an exothermic reaction, so heat was released. Delta H solution can be positive (endothermic, gets cold) or negative (exothermic, gets hot) Solvation- solvent molecules interacting favorably (attractive forces) with solute molecules (ions). Explains how stuff dissolves. *** *** if solvent is H2O, its called hydration OVERALL DISSOLUTION : NaCl (s) (---H2O liq- ) Na+(aq) + Cl- (aq) This is steps 2 + 3 combined…almost
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Unformatted text preview: Hydration of Na+ : Steps 2+3 : Na + Cl (H2O) Na + Cl Delta H solution = Delta H1 + Delta H2 + Delta H3 Delta H1=C.Lattice (+ must be) Delta H2 + Delta H3 = Delta H hydration (- must be) Hydration sphere H2O molecules encapsulating the corner Chlorine ions in salt crystals What factors influence dissolving? All spontaneous changes need a negative delta G Delta G = Delta H T*DeltaS [Rare] H negative, T*delta S positive always have negative delta G at all temperatures [Usually] H positive , S positive non-spontaneous at low temperature, spontaneous at high temperatures Driving force for making solutions : entropy increases...
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Friday, January 29th, 2010 - Hydration of Na+ : Steps 2+3 :...

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