CHEMISTRY 162 Midterm 2 Review

Than the atoms of the host crystal thus the holes can

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than the atoms of the host crystal, thus the holes can be viewed as charge carriers P-n junctions Connection of p and n type Creates charge buildup Ionic Solids Stable, high-melting point substances held together by the strong electrostatic forces  that exist between oppositely charged ions Large ions (anions) are packed in one of the closest packing arrangements (hcp or ccp)  where the smaller cations fit into holes among the closest packed anions Holes Trigonal- three spheres in the same layer Tetrahedral- sphere sits in the simple of the three spheres in an adjacent layer r=0.225R Octahedral- two sets of three spheres in adjoining layers of the closest packed  structures r=0.414R
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05:59 Properties of Solution
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05:59 Mass % (parts by mass): (g of solute)/(g of solution) * 100% Mole fraction of component A: Xa = (mass/vol of solute)/(total mass/vol) Molality: (moles of solute/kg of solvent) Molarity: (mols of solute/L of solvent) Enthalpy (heat) of solution Overall enthalpy change in the formation of a solution Hdelta(soln)= Hdelta(1) + Hdelta(2) + … Exothermic= negative net energy Endothermic= positive net energy Enthalpy (heat) of hyrdration Enthalpy change associated with the dispersal of a gaseous solute in water Standard enthalpy of solution Hdelta(hyd) + Hdelta(soln) Sdelta Smaller (or more negative) the less soluble More ordered, more soluble Pressure effects Little effects on the solubilities of solids or liquids, but increases the solubility of a gas Henry’s Law: P=KhX Amount of gas dissolved in a solution is directly proportional to the pressure of the gas  above the solution
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05:59 When gas is in water, as temperature increases, solubility decreases Raoult’s Law Psoln=Xslov*Psovl Vapor pressure Nonvolatile substance lowers the vapor pressure of a solvent When graphed, if lines are above the value calculated for Raoults Law, positive  deviation When graphed, if lines are below the value calculated for Raoults Law, negative  deviation Boiling-point elevation Nonvolatile solute elevates the boiling point of the solvent Tdelta= Kbm(solute) Kb=molal boiling point elevation constant Freezing Point depression The water in the solution has a lower vapor pressure than that of pure ice, thus the fp is  lowered Antifreeze Tdelta=Kfm(solute) Osmotic pressure
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