2. Polar Covalent Bonds: Acids and Bases

Question 1

Covalent bonds can have ionic character

Answer 1

Polar Covalent bonds

Question 2

Polar Covalent bonds

Answer 2

Bonding electrons attracted more strongly by one
atom than by the other

Electron distribution between atoms is not
symmetrical

Difference in EN of atoms < 2

Question 3

intrinsic ability of an atom to attract the shared electrons in a covalent bond

Answer 3

Electronegativity

Question 4

Metals on left side of periodic table attract electrons weakly, lower EN

Question 5

Halogens and other reactive nonmetals on right side
of periodic table attract electrons strongly, higher
electronegativities

Question 6

atoms with similar EN

Answer 6

Nonpolar covalent bonds

Question 7

Ionic Bonds

Answer 7

Difference in EN > 2

Question 8

shifting of electrons in a bond in
response to EN of nearby atoms

Answer 8

Inductive effect

Question 9

show calculated
charge distributions

Colors indicate electron-rich (red) and electron-poor (blue) regions

Arrows indicate direction
of bond polarity

Answer 9

Electrostatic potential
maps

Question 10

Net molecular polarity, due to difference in
summed charges

Answer 10

Dipole moment

Question 11

In symmetrical molecules, the dipole moments of each bond has one in the opposite direction. The effects of the local dipoles cancel each other

Question 12

Neutral molecules with both a “+” and a “-” are called?

Answer 12

Dipolar

Question 13

Formal charge formula:

Valence electron - ( Bonding + Dots)

Question 14

it is a hybrid of the two resonance forms

Answer 14

Resonance hybrid

Question 15

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Question 16

The resonance hybrid is more stable than any
individual resonance form would be

Question 17

shows that a pair of electrons moves
from the atom or bond at the tail of the arrow to the
atom or bond at the head of the arrow

Answer 17

A curved arrow

Question 18

Any three-atom grouping with a multiple bond
has two resonance forms

Question 19

a substance that donates a hydrogen ion (H+)

Answer 19

Bronsted acid

Question 20

a substance that accepts
the H+

Answer 20

Bronsted base

Question 21

“proton” is a synonym for H+
- loss of an
electron from H leaving the bare nucleus—a
proton

Question 22

The equilibrium constant (Keq) for the reaction of an
acid (HA) with water to form hydronium ion and the
conjugate base (A-
) is a measure related to the
strength of the acid

Question 23

High pKa = weak acid, strong base

Low pKa = strong acid, weak base (is proportional to the energy difference between products and reactants)

Question 24

Stronger acids have larger Keq

Question 25

pKa = -log Ka

Question 26

pKa of water is 15.74

Question 27

The stronger base holds the proton more tightly

Question 28

characterized by the presence of positively polarized hydrogen atom

Answer 28

Organic Acids

Question 29

Have an atom with a lone pair of electrons that can bond to H+

Answer 29

Organic Bases

Question 30

Nitrogen-containing compounds derived from ammonia are the most common organic bases Oxygen-containing compounds can react as bases when with a strong acid or as acids with strong bases

Question 31

are electron pair acceptors; electron deficient; + charged; boron

Answer 31

Lewis acids

Question 32

are electron pair donors; - charged; lone pairs

Answer 32

Lewis bases

Question 33

Brønsted acids are not Lewis acids because they cannot accept an electron pair directly (only a proton would be a Lewis acid)

Question 34

The Lewis definition of acidity includes metal cations, such as Mg2+ - They accept a pair of electrons when they form a bond to a base

Question 35

Group 3A elements, such as BF3 (boron trifluoride) and AlCl3 (aluminum chloride) , are Lewis acids because they have unfilled valence orbitals and can accept electron pairs from Lewis bases

Question 36

Transition-metal compounds, such as TiCl4 (titanium tetrachloride), FeCl3 (ferric chloride or iron (III) chloride), ZnCl2 (zinc chloride), and SnCl4 (tin (IV) chloride or stannic chloride), are Lewis acids

Question 37

can accept protons as well as Lewis acids, therefore the definition encompasses that for Brønsted bases

Answer 37

Lewis Bases

Question 38

Most oxygen- and nitrogen-containing organic compounds are Lewis bases because they have lone pairs of electrons

Question 39

Noncovalent Interactions

Answer 39

- Dipole-dipole forces - Dispersion forces - Hydrogen bonds

Question 40

Occur between polar molecules as a result of electrostatic interactions among dipoles; Forces can be attractive of repulsive depending on orientation of the molecules

Answer 40

Dipole-dipole

Question 41

Occur between all neighboring molecules and arise because the electron distribution within molecules that are constantly changing

Answer 41

Dispersion Forces

Question 42

Most important noncovalent interaction in biological molecules

Answer 42

Hydrogen bond forces

Question 43

The strength Brønsted acid is related to the -1 times the logarithm of the acidity constant, pKa. Weaker acids have higher pKa’s

Question 44

From strongest to weakest, it would be ion-dipole, hydrogen bonding, dipole-dipole, dipole-induced dipole, london dispersion forces.

Question 45

Bronsted acid = H+ donors Bronsted base = H+ acceptors Lewis acid = e- acceptors Lewis base = e- donors