Chapter 2 - Aqueous Chemistry

Front 1

T or F: Water is abundant in living organisms

Back 1

True

Front 2

Why does water have tetrahedral geometry?

Back 2

Because of its electronic structure

Front 3

What are the two primary characteristics of the electronic structure of water?

Back 3

1. Oxygen has two lone pair

2. An electron from hydrogen is shared with one from oxygen

Front 4

Is water polar or nonpolar?

Back 4

Polar

Front 5

T or F: Same charges attract

Back 5

False

Front 6

What is the charge of oxygen?

Back 6

Partial negative charge

Front 7

What is the charge of hydrogen?

Back 7

Partial positive charge

Front 8

How are the oxygens affected in the way water molecules orient?

Back 8

Oxygens are positioned near hydrogen(s) in a neighboring molecule

Front 9

What is a hydrogen bond?

Back 9

A noncovalent interaction between a molecule containing an electronegative atom and another molecule containing an electropositive hydrogen

Front 10

What are two examples of electronegative atoms that can occur in hydrogen bonding?

Back 10

Oxygen and nitrogen

Front 11

Can water form hydrogen bonds?

Back 11

Yes

Front 12

What are the two components of a hydrogen bond?

Back 12

1. Hydrogen bond donor = H-A

2. Hydrogen bond acceptor = B

Front 13

What are two key players in hydrogen bonding in biomolecules?

Back 13

1. Hydroxyl functional group

2. Amine groups

Front 14

What happens to the orbitals in a covalent bond?

Back 14

The atoms are too close, their orbitals overlap

Front 15

What happens to the orbitals in a hydrogen bond?

Back 15

When the orbitals are as close as possible without overlapping

Front 16

What are Van-der Waals interactions?

Back 16

Electrostatic forces, involving dipoles, between molecules

Front 17

What is the hydrophobic effect?

Back 17

The phenomenon by which nonpolar molecules aggregate to avoid contact with hydrophilic molecules, particularly water

Front 18

What do nonpolar molecules tend to do in polar solvents?

Back 18

Aggregate

Front 19

Is the hydrophobic effect favorable or unfavorable?

Back 19

Favorable

Front 20

What is high entropy?

Back 20

Higher disorder of water

Front 21

What is lower entropy?

Back 21

Lower disorder of water

Front 22

Concerning nonpolar molecules in water, describe what is unfavorable?

Back 22

Many H2O molecules are ordered around the nonpolar molecules

Front 23

Concerning nonpolar molecules in water, describe what is favorable?

Back 23

Fewer H2O molecules are ordered around the nonpolar molecules

Front 24

T or F: Most lipids are not amphiphilic

Back 24

False

Front 25

What are fatty acids?

Back 25

A type of lipid composed of a hydrophilic head group and a hydrophobic (nonpolar) hydrocarbon tail

Front 26

What is an amphiphile?

Back 26

Molecule composed of a hydrophilic head group and a hydrophobic (nonpolar) hydrocarbon tail

Front 27

What do amphiphilic molecules do in aqueous solutions?

Back 27

Form miscelles and lipid bilayers

Front 28

How is a hydrophobic molecule classified?

Back 28

Nonpolar

Front 29

How is a hydrophilic molecule classified?

Back 29

Polar

Front 30

What is the symbol for the ionization constant for water?

Back 30

Kw

Front 31

What is the known value of the ionization constant for water?

Back 31

Kw = [H+] x [OH-] = 10^-14

Front 32

What are the characteristics of pure water?

Back 32

[H+] = [OH-] = 10^-7 M = neutral

Front 33

How is a solution in which [H+] > 10^-7 M classified?

Back 33

Acidic

Front 34

How is a solution in which [H+] < 10^-7 M classified?

Back 34

Basic

Front 35

What is the formula for calculating pH?

Back 35

pH = -log [H+]

Front 36

What is the pH for a neutral reaction?

Back 36

7

Front 37

What is the pH for an acidic reaction?

Back 37

pH < 7

Front 38

What is the pH for a basic reaction?

Back 38

pH >7

Front 39

What type of relationship does [H+] and [OH-} have?

Back 39

An inverse relationship; as [H+] increases, [OH-] decreases

Front 40

How is pH related to [H+]?

Back 40

Logarithmically proportional

Front 41

When are pK and pH the same?

Back 41

At which the acid is half dissociated

Front 42

What are the characteristics when the protonated form predominates?

Back 42

pH < pK

Front 43

What are the characteristics when the deprotonated form predominates?

Back 43

pH > pK

Front 44

How do pH and pK related to protonated and deprotonated forms?

Back 44

pH < pK = protonated

pH > pK = deprotonated

Front 45

When a pK is larger, what does this mean for an acid?

Back 45

It is a weak acid (less likely it will donate a proton)

Front 46

What is the pH formula involving pK?

Back 46

pH = pK + log {[A-] / [HA]}

Front 47

What is the structure of an amino acid when the pH < 3.5?

Back 47

COOH -- C -- NH3+

Front 48

What is the structure of an amino acid with 3.5 < pH < 9?

Back 48

COO- -- C -- NH3+

Front 49

What is the structure of an amino acid when the pH > 9?

Back 49

COO- -- C -- NH2

Front 50

What happens to an amino acid when the pH < 3.5?

Back 50

Amino acids have both protons and a net positive charge

COOH and NH3+

Front 51

What happens to an amino acid when 3.5 < pH < 9?

Back 51

Amino acids lose the proton on the carboxyl carbon and zwitterions; charge is neutral

COO- and NH3+

Front 52

What happens to an amino acid when pH > 9?

Back 52

Amino acids have lost bother protons and have a net negative charge

COO- and NH2

Front 53

Is an acid a proton donor or acceptor?

Back 53

Proton donor

Front 54

Is a base a proton donor or acceptor?

Back 54

Proton acceptor

Front 55

How can the pH of a solution be altered?

Back 55

By adding a strong base/acid

Front 56

What happens to the association of a strong acid/base?

Back 56

Completely dissociates

Front 57

What happens to the association of a weak acid/base?

Back 57

Partially dissociates

Front 58

What is a buffer?

Back 58

A solution containing a weak acid and its conjugate base

Front 59

What are some weak acids commonly found in biological systems?

Back 59

Acetic acid

Propionic acid

Sorbic acid

Benzoic acid

Succinic acid

Front 60

What is the Henderson-Hasselbalch equation?

Back 60

pH = pK + log { [A-] / [HA] }

Front 61

When is the Henderson-Hasselbalch equation used?

Back 61

It can be used to figure out the ratio of acid to base forms of a buffer that are required to make the buffer at a given pH

Front 62

When can the Henderson-Hasselbalch equation be used to determine the pH of a solution?

Back 62

When given the concentrations of HA and A-

Front 63

What is a generic buffer equation?

Back 63

HA <----> H + A-

Front 64

T or F: Buffer solutions can resist change in pH

Back 64

True

Front 65

What is the rule of thumb for a buffer zone for when [A-] = 10 [HA]?

Back 65

pH = pK +log(10) = pK + 1

Front 66

What is the rule of thumb for a buffer zone for when [HA] = 10 [A-]?

Back 66

pH = pK + log(0.1) = pK - 1

Front 67

When do buffers tend to resist changes in pH?

Back 67

When [A-] and [HA] differ by no more than a factor of ten

Front 68

What is a dipole?

Back 68

An interaction between two strongly polar groups

Front 69

What is the strength of a dipole?

Back 69

About 9 kJ . mol-1

Front 70

What is the definition of electronegativity?

Back 70

A measure of an atom's affinity for electrons

Front 71

Where on the periodic table is an element more electronegative?

Back 71

The top right

Front 72

What is another word for "water loving"?

Back 72

Hydrophilic

Front 73

What are examples of hydrophilic molecules?

Back 73

Glucose and other readily hydrated substances

Front 74

What is another word for "water fearing"?

Back 74

Hydrophobic

Front 75

T or F: Hydrophobic molecules are relatively soluble in water

Back 75

False

Front 76

What is the difference in how micelles and lipid bilayers are formed by amphiphiles in aqueous solutions?

Back 76

Micelles are typically formed by lipids with ONE nonpolar tail

Lipid bilayers are typically formed by lipids with TWO nonpolar tails