Auburn University - BCHE 5180Study Guide for Test 1

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Water/Buffers • Properties of Water: o Water is a solvent and is polar (like dissolves like)  Polar due to oxygen being more electronegative than hydrogen  Also undergoes hydrogen bonding ... between molecular for intermolecular interactions as well as London-dispersion and Van der waals forces • Hydrogen bonding is present between molecules bonding with hydrogen that have O, N, or F. (note no Carbon) • These bonds also allow ice to have a lower density than liquid water  The ability of a molecule to form hydrogen bonds with water defines its solubility in water, and the inability to form hydrogen bonds with water is the basis of hydrophobic interactions.  Polar compounds dissolve in water by forming new H bonds with the solute and the process overall being a dynamic process (constant breaking and formation of H bonds.)  Water also dissolves salts extremely well via ion-dipole interactions • Increase in entropy when a salt is dissolved in water is called Hydration.  Non-polar substances have a different story • Non-polar substances due to lack of hydrogen bonding and very little difference in electronegativities. • In water, move in order to minimize the amount of surface exposed to water which is entropically driven. • Water forms a cage around the non polar solute which leads to a decrease in entropy for water. • Form chains around the hydrophobic areas • Hydrophobic interactions – ‘forces’ that hold the non polar regions of the molecules [Show More]

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