Ch.2: Acids & Bases

Question 1

acid vs. base

Answer 1

An acid is a species that donates a proton.

A base is a species that accepts a proton.

Question 2

Lewis acid vs. Lewis base

Answer 2

A Lewis acid is a species that accepts a share in an electron pair.
A Lewis base is a species that donates a share in an electron pair.

Question 3

acidity vs. basicity

Answer 3

Acidity is a measure of the tendency of a compound to lose a proton.
Basicity is a measure of a compound’s affinity for a proton.

Question 4

The stronger the acid, the (1) _____ its conjugate base and the (2) ______ its pKa value.

Answer 4

(1) weaker

(2) smaller

Question 5

The strength of an acid is given by the ___________ .

Answer 5

acid dissociation constant (Ka)

Question 6

What are the approximate pKa values for the following: protonated alcohols, protonated carboxylic acids, protonated water, carboxylic acids, protonated amines, alcohols and water?

Answer 6

Approximate pKa values: 
Protonated alcohols, protonated carboxylic acids, protonated water are all less than 0. 
Carboxylic acids are about 5.
Protonated amines are about 10.
Alcohols and water are about 15.

Question 7

In acid-base reactions, the equilibrium favors formation of the _______ acid.

Answer 7

weaker

Question 8

The strength of an acid is determined by the (1) ________ of its conjugate base: the more (2) ________ the base, the stronger its conjugate acid.

Answer 8

(1) stability

2) stable (weaker

Question 9

When atoms are similar in size, the stronger acid will have its hydrogen attached to the (1) ______________ atom. When atoms are very different in size, the stronger acid will have its hydrogen attached to the (2) _____________ atom.

Answer 9

(1) more electronegative

(2) the larger

Question 10

Hybridization affects acidity because _____________________________ .

Answer 10

an sp hybridized atom is more electronegative than an sp2 hybridized atom, which is more electronegative than an sp3 hybridized atom

Question 11

__________________ increases acidity: the more electronegative the electron-withdrawing group and the closer it is to the acidic hydrogen, the stronger the acid.

Answer 11

Inductive electron withdrawal

Question 12

_____________ (electrons that are shared by more than two atoms) stabilize a compound.

Answer 12

Delocalized electrons

Question 13

What is a resonance hybrid?

Answer 13

A resonance hybrid is a composite of the resonance contributors, structures that differ only in the location of their pi electrons and lone-pair electrons.

Question 14

What is the purpose of the Henderson-Hasselbalch equation?

Answer 14

The Henderson-Hasselbalch equation gives the relationship between pKa and pH: a compound exists primarily in its acidic form (with its proton) in solutions more acidic than its pKa value and primarily in its basic form (without its proton) in solutions more basic than its pKa value.

Question 15

What is a buffer solution?

Answer 15

A buffer solution contains both a weak acid and its conjugate base.

Question 16

Explain the difference among these terms: acid, Lewis acid, and electrophile.

Answer 16

Acid is used to mean a proton-donating acid.
Lewis acid is used to refer to non-proton-donating acids such as AlCl3 or BF3.
Electrophile refers to both proton-donating and non-proton-donating acids.

Question 17

Explain the difference between these terms: base and nucleophile.

Answer 17

Base is used to mean a compound that shares its lone pair with a proton.
Nucleophile is used for a compound that shares its lone pair with an atom other than a proton.