Ch3 Acids, Bases and Buffers

Question 1

Conjugate acid-base pairs

Answer 1

HA + B <=> BH+ + A-
base + acid <=> conjugate acid + conjugate base

Question 2

Conjugate acid

Answer 2

Species with extra proton

Question 3

Conjugate base

Answer 3

Species without proton

Question 4

Mono,di or tribasic acids

Answer 4

acids can produce more than one conjugate base depending on how many hydrogen ions they donate

Question 5

Strong acids

Answer 5

highly ionised in aqueous solution to produce H+ ions

Question 6

Weak acid

Answer 6

partially ionised in aqueous solution to produce H+ ions

Question 7

Acid dissociation constant

Answer 7

[HA(aq)]

Question 8

Hydrogen ion conc of strong acid using Ka

Answer 8

strong acids ionised completely so have same H+ conc as HA conc

Question 9

Hydrogen ion conc of weak acid using Ka

Answer 9

[H+] = square root Ka x conc of solution

because [H+] is same as [A-]

Question 10

pH formula

Answer 10

-log[H+]

Question 11

Hydrogen ion conc from pH

Answer 11

10^-pH

Question 12

Ionic product of water Kw

Answer 12

[OH-][H+] = 1x10^-14

Question 12

Buffer solution

Answer 12

solution that resists a change in pH when a small quantity of acid or alkali is added

Question 13

Key points for buffer solution

Answer 13

weak acid + salt from acid

Question 14

Adding alkali to buffer solution

Answer 14

OH- reacts with H+ on right side equilibrium to produce H2O so [H+] decreases
pH increases
Equilibrium shifts to right to counteract so [H+] increases
pH decreases

Question 15

Add acid

Answer 15

H+ increases [H+] conc
pH decreases
equilibrium position shift to left to counteract
[H+] decreases
pH increases

Question 16

ka buffer solution

Answer 16

[salt][H+] / [acid]
= ka

Question 17

pH buffer solution

Answer 17

-log(Ka[acid] / [salt])

Question 18

Strong acid

Answer 18

HCl
HNO3
H3PO4
H2SO4

Question 19

Strong base

Answer 19

NaOH
metal hydroxides

Question 20

Weak acid

Answer 20

CH3COOH

Question 21

Weak base

Answer 21

NH3

Question 22

Equivalence point

Answer 22

enough acid has been added to react completely with all of the base

Question 23

Phenopthalein

Answer 23

acid - colourless
pink-alkali

changes around pH9

Question 24

methyl orange

Answer 24

acid- red
base- yellow

change around pH 4