CHEM 120 Lecture Notes - Lecture 15: Ionic Compound, Potassium Sulfate, Ionic Bonding
15 Jun 2018
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READ CHAPTER 12.4
CHEM 120: SOLUTIONS AND COLLOIDS
Definitions:
- Solutions: mixture where solute is present as individual atoms, ions or small molecules
- Colloids: multiphase mixture hetero where solute is present as macros or small molecule
aggregates
- Solute: the least amount component in solution compromised of substances within a solution
- Solvent: most abundant component in a solution which determines the state of solution
o Concentrated → Solute / Dilute → Solute
- Solubility: maximum amount of solute that dissolves in a fixe quantity of a solvent a given T
Like Dissolves Like:
Solubility is favoured when the interactions are similar, (e.g. Compound A and Compound B → solubility
is favoured when A-B interactions are like A-A and B-B interactions)
- Oil has dispersion forces, water has H-bond → you get dipole-induced dipole which does not
favour mixing
Dissolving:
❖ Non-polar molecules are soluble in non-polar solvents (CCL4 and C6H6)
❖ Ionic compounds are more soluble in polar solvents (NaCl in H20)
❖ Ideal solution → ∆� = 0 → the IF is equal to the IF in forming step 3
❖ Non-Ideal solution → ∆� ≠ 0
❖ Large positive delta H you have a heterogenous mixture (oil & water), enthalpy is too great to
overcome
When a solution forms there are solute-solvent interactions: but can only occur if the forces within the
solute and the solvent are like the forces that replace them
- OH groups on sucrose provides sites for hydrogen bonding
Salts: when the ionic species dissolves → replace the ionic bonding with ion-dipole bonds (NaCl (aq))
Hydration: solvation shells form when the water molecules surround the cation (i.e. potassium sulfate
releases more energy, more water molecules surround)
- Hydration energy > Lattice energy, more favourable the dissolution
- Electrolytes: solutions formed from ionic species (conductors)
- Increase hydrocarbon chain, solubility decreases
- Alcohols are organic compounds that have dual polarity; OH group on the alcohol is polar and
interacts with water through H bonds with hexane with weak dipole-induced dipole interactions
(hydration portion is non-polar)
Metals: do not dissolve in water or non-polar solvents (some may react in water while others react in
acidic solutions)
- Some may dissolve in acid, etc.
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Document Summary
Solutions: mixture where solute is present as individual atoms, ions or small molecules. Colloids: multiphase mixture hetero where solute is present as macros or small molecule aggregates. Solute: the least amount component in solution compromised of substances within a solution. Solvent: most abundant component in a solution which determines the state of solution: concentrated solute (cid:1371) / dilute solute (cid:1373) Solubility: maximum amount of solute that dissolves in a fixe quantity of a solvent a given t. Solubility is favoured when the interactions are similar, (e. g. compound a and compound b solubility is favoured when a-b interactions are like a-a and b-b interactions) Oil has dispersion forces, water has h-bond you get dipole-induced dipole which does not favour mixing. Non-polar molecules are soluble in non-polar solvents (ccl4 and c6h6) Ionic compounds are more soluble in polar solvents (nacl in h20) Ideal solution =0 the if is equal to the if in forming step 3.
