pKa values

Question 1

Answer 1

Hydronium ion & Protonated alcohols

Approximate pKa value:

-2

Question 2

Answer 2

Carboxylic acids

Approximate pKa value:

5

Question 3

Answer 3

Alcohol & water

Approximate pKa value:

16

Question 4

Answer 4

Phenol

Approximate pKa value:

9

Question 5

Answer 5

Protonated Carbonyl Group

Z = H, C, OR, NH2, NHR, NR2

Approximate pKa value:

-5

Question 6

Answer 6

Ketone

Approximate pKa value:

20

Question 7

Answer 7

Ester

Approximate pKa value:

25

Question 8

Answer 8

Ammonium ion

Approximate pKa value:

9

Question 9

Answer 9

Protonated amines

Approximate pKa value:

11

Question 10

Answer 10

Thiol

Approximate pKa value:

10

Question 11

Answer 11

Amine

Approximate pKa value:

33

Question 12

Answer 12

Diisopropylamine

Approximate pKa value:

37

Question 13

Answer 13

Amide

Approximate pKa value:

15

Question 14

Answer 14

Alkane

Approximate pKa value:

60

Question 15

Answer 15

Alkene

Approximate pKa value:

44

Question 16

Answer 16

Alkyne

Approximate pKa value:

25

Question 17

Answer 17

Sulfuric acid

Approximate pKa value:

-9

Question 18

Answer 18

Hydrochloric acid

Approximate pKa value:

-7

Question 19

Answer 19

β-Diketone

R = carbon

Approximate pKa value:

10

Question 20

Answer 20

β-Ketoester

R = carbon

Approximate pKa value:

12

Question 21

Answer 21

Malonate Ester

R = carbon

Approximate pKa value:

14

Question 22

Answer 22

Hydrogen gas

Approximate pKa value:

36

Question 23

Define: pKa

Answer 23

• The pKa value is one method used to indicate the strength of an acid.
• pKa is the negative log of the acid dissociation constant or Ka value.
• A lower pKa value indicates a stronger acid.
• That is, the lower value indicates the acid more fully dissociates in water.

Question 24

What is a strong acid?

Answer 24

• Strong acids dissociate completely to give weak conjugate base pairs.
• Ka > 1
• pKa < 1
• eg., HCl

Question 25

What is a weak acid?

Answer 25

• Weak acids dissociate to a small extent to give strong conjugate base pairs.
• Ka < 1
• pKa > 1