Chapter 2: Aqueous Chemistry Flashcards
How much water is in the body?
60%
Describe water’s structure
tetrahedral geometry, sp3 hybridization, polar
Why is water’s structure continually flickering?
as molecules rotate, bend and reorient themselves, water continually flickers due to the lifetime of HBs being approx 10^-12 picoseconds
Why does water remain a liquid at room temperature and other molecules do not?
because water is cohesive due to its ability to form HB which accounts for its high surface tension
Why does LDF occur?
occurs between nonpolar molecule and as a result of small fluctuations in their distribution of electrons that create a temporary separation of charge
Elelctronegativity
is a measure of an atom’s affinity for electrons
_______ is the most electronegative atom
fluorine
What are the key players in hydrogen bonding in biomolecules?
hydroxyl groups and amine groups
List the electrostatic interactions
ionic bond, HB, van der Waals interactions (dipole-dipole interaction, LDF)
Define dielectric constant
measure of a solvent’s ability to diminish the electrostatic attractions between dissolved ions
- water has a relatively high dielectric constant
What happens when a nonpolar molecule is placed in water?
- nonpolar molecule would require hydration
- hydration of a non-polar molecule results in water molecules being unable to participate in hydrogen bonding
- this decreases their freedom to move, resulting in a loss of entropy
Hydrophobic effect
- exclusion of nonpolar substances from an aqueous solution
- entropy driven: there are no attractive forces holding the non-polar molecules together, rather they aggregate because they are driven out by the unfavourable entropy of hydrating non-polar molecules individually
Since amphiphilic molecules are both hydrophilic and hydrophobic, what type of interactions do they experience?
- amphiphilic molecules experience both hydrophilic interactions and the hydrophobic effect
- polar groups of amphipholic mol. orient themselves towards the solvent mol and are therefore hydrated
- nonpolar groups tend to aggregate due to the hydrophobic effect
Micelles vs. bilayers
- both are formed by collection of amphiphilic mol
- one-tailed lipids form micelles
- two-tailed lipids form bilayers
Why are vesicles formed?
to eliminate its solvent-exposed edges
Ionic composition of intracellular fluid
mostly potassium, then sodium and chlorine respectively
Ionic composition of extracellular fluid
mostly sodium and chlorine, then potassium
Why doesn’t hydrogen ion exist freely in solution?
because it has very strong energy so it would exist as a hydronium ion or in a cluster
acid
- substance that can donate a proton
- addition of an acid increases [H+] and decrease pH
- strong acids have K»_space;1
base
- substance that can accept a proton
- addition of a base increases pH
Polyprotic acid
compound with more than one acidic hydrogen
How are buffers prepared?
is prepared from a weak acid and the salt of its conjugate base. They are mixed together in the appropriate ratio according to HH equation and the final pH is adjusted if necessary by adding a small amount of concentrated HCl or NaOH.
Le Chatelier’s principle
states that a change in concentration of one reactant will shift the concentration of other reactants in other reactants in order to restore equilibrium
