Chapter 2: Aqueous Chemistry

Question 1

How much water is in the body?

Answer 1

60%

Question 2

Describe water’s structure

Answer 2

tetrahedral geometry, sp3 hybridization, polar

Question 3

Why is water’s structure continually flickering?

Answer 3

as molecules rotate, bend and reorient themselves, water continually flickers due to the lifetime of HBs being approx 10^-12 picoseconds

Question 4

Why does water remain a liquid at room temperature and other molecules do not?

Answer 4

because water is cohesive due to its ability to form HB which accounts for its high surface tension

Question 5

Why does LDF occur?

Answer 5

occurs between nonpolar molecule and as a result of small fluctuations in their distribution of electrons that create a temporary separation of charge

Question 6

Elelctronegativity

Answer 6

is a measure of an atom’s affinity for electrons

Question 7

_______ is the most electronegative atom

Answer 7

fluorine

Question 8

What are the key players in hydrogen bonding in biomolecules?

Answer 8

hydroxyl groups and amine groups

Question 9

List the electrostatic interactions

Answer 9

ionic bond, HB, van der Waals interactions (dipole-dipole interaction, LDF)

Question 10

Define dielectric constant

Answer 10

measure of a solvent’s ability to diminish the electrostatic attractions between dissolved ions
- water has a relatively high dielectric constant

Question 11

What happens when a nonpolar molecule is placed in water?

Answer 11

• 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

Question 12

Hydrophobic effect

Answer 12

• 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

Question 13

Since amphiphilic molecules are both hydrophilic and hydrophobic, what type of interactions do they experience?

Answer 13

• 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

Question 14

Micelles vs. bilayers

Answer 14

• both are formed by collection of amphiphilic mol
• one-tailed lipids form micelles
• two-tailed lipids form bilayers

Question 15

Why are vesicles formed?

Answer 15

to eliminate its solvent-exposed edges

Question 16

Ionic composition of intracellular fluid

Answer 16

mostly potassium, then sodium and chlorine respectively

Question 17

Ionic composition of extracellular fluid

Answer 17

mostly sodium and chlorine, then potassium

Question 18

Why doesn’t hydrogen ion exist freely in solution?

Answer 18

because it has very strong energy so it would exist as a hydronium ion or in a cluster

Question 19

acid

Answer 19

• substance that can donate a proton
• addition of an acid increases [H+] and decrease pH
• strong acids have K&raquo_space;1

Question 20

base

Answer 20

• substance that can accept a proton

- addition of a base increases pH

Question 21

Polyprotic acid

Answer 21

compound with more than one acidic hydrogen

Question 22

How are buffers prepared?

Answer 22

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.

Question 23

Le Chatelier’s principle

Answer 23

states that a change in concentration of one reactant will shift the concentration of other reactants in other reactants in order to restore equilibrium