the acid dissociation constant Ka

Question 1

how can the dissociation of any weak acid be shown?

Answer 1

HA (EQUI ARROW) H+ +A-

Question 2

how is the acid dissociation constant calculated? units are?

Answer 2

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

UNITS = MOLDM^-3

Question 3

what type of acid is the ka expression written for mainly

Answer 3

weak acid

Question 4

write Ka expression for ethanoic acid?

Answer 4

[H+][CH3COO-] / [CH3COOH] (all aq)

Question 5

what are recorded Ka values usually standardised at?

Answer 5

room temp

Question 6

what does Ka change with?

Answer 6

temp

Question 7

what happens to the position of equilibrium the larger the Ka value is?

Answer 7

the further the equilibrium is to the right

Question 8

larger Ka value =

Answer 8

• greater dissociation

- greater acid strength

Question 9

how do you turn Ka into pKa? and vice versa fo weak acids?

Answer 9

pka = -log(ka)

ka = 10^-pka

Question 10

list 4 weak acids and their formulas

Answer 10

nitrous acid =HNO2
methanoic acid= HCOOH
ethanoic acid
chloric (I) acid = HCLO

Question 11

what happens to Ka and pka values the stronger the acid is?

Answer 11

• larger Ka

- smaller pka

Question 12

what happens to Ka and pka values the weaker the acid is?

Answer 12

• smaller ka value

- larger pka value

Question 13

are ka or pka values easier to use for comparison of strength of weak acids?

Answer 13

pka

Question 14

what is the formula of sulphurous acid

Answer 14

H2SO3