Chapter 14 Solutions

Chapter 14 Solutions - 1 Energy is absorbed to open...

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LIKE DISSOLVES LIKE THE SOLUBILITY OF SOLIDS DEPENDS ON THE RELATIVE STRENGTHS OF INTERMOLECULAR ATTRACTIONS Hydration Solvation ΔH soln , m (molar enthalpy of solution) – the total energy absorbed or relased when a solute dissolves in a solvent at constant pressure Lattice energy – the energy required to separate 1 mol of a crystalline compound into gaseous particles Solvation energy – the enthalpy change when gaseous solute particles obtained from 1 mol of solute are dissolved in a solvent (H 2 O = hydration energy) SOLUTION OF A LIQUID IN ANOTHER LIQUID IN THREE STEPS 1. Expand the solute liquid (+) 2. expand the solvent liquid (+) 3. mix the expanded liquids (-) Ideal sol’n – same attractive forces; ΔH soln,m = 0 GAS SOLUBILITY – weak attractions; expansion energy is neglible
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Unformatted text preview: 1. Energy is absorbed to open “pockets” in the solvent that can hold gas molecules 2. Energy is released when gas molecules are popped into these pockets. 3. Heats of sol’n for gases in organic solvents are often endothermic 4. heats of sol’n for gases in water are often exothermic (pockets already open) saturated solution – dynamic equilibrium exists between the un-dissolved solute and the solute in the solution A SUBSTANCE’S SOLUBILITY CHANGES WITH TEMPERATURE (gas and liquid) GASES BECOME MORE SOLUBLE AT HIGHER PRESSURES HENRY’S LAW – “pressure – solubility law” C gas = k H P gas GASES WITH POLAR BONDS IN THEIR MOLECULES ARE MORE SOLUBLE IN WATER...
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