20.3 The Acid Dissociation Constant Ka

Question 1

What is the Acid Dissociation?

Answer 1

Ka=([H+][A-])/[HA]

Question 2

What can Ka be used for?

Answer 2

Weak Acids

Question 3

Effect on equilibrium with increased Ka value

Answer 3

Further equilibrium to the right

Question 4

Effect on dissociation and acid strength with a larger Ka value

Answer 4

Increased dissociation, greater acid strength

Question 5

What temperature are Ka values standardised at?

Answer 5

25C or 298K

Question 6

What’s the problem with using Ka values

Answer 6

It’s difficult to compare numbers with negative indices

So converting it to pKa is more manageable

Question 7

Calculating pKa?

Answer 7

-log(Ka)

Question 8

Calculating Ka?

Answer 8

10^-pKa

Question 9

Increased acid strength shows…?

effect on Ka, pKa and type of acid

Answer 9

Ka increases
pKa decreases
Monobasic

Question 10

Decreased acid strength shows…?

effect on Ka, pKa and type of acid

Answer 10

Ka decreases
pKa increases
Tribasic

Question 11

What can pKa values be used for?

Answer 11

to compare the strength of weak acids, particularly in biological systems