Ch. 2 Acid- Base Equilibrium

Question 1

What is the Arrhenius theory of acids and bases

Answer 1

• Acid: a substance that produces H+ ions in solution

- Base: a substance that produces OH- ions in solution

Question 2

What are acids and bases in terms of protons

Answer 2

Acid: a proton (H+) donor

Base: a proton (H+) acceptor

Question 3

What is the strength of a solution

Answer 3

ability/extent dissociate/ionize in solution

Question 4

Do acids and bases ionise or dissociate

Answer 4

acid= ionise
base= dissociate

Question 5

What is the difference between a conjugate base pair

Answer 5

Differ by one hydrogen

Question 6

Formula for Ph

Answer 6

pH= -log 10 [H3O+]

Question 7

Formula for hydronium ion from pH

Answer 7

[H3O+]=10-pH

Question 8

What changes to pH calculations when substances are polyprotic

Answer 8

multiply concentration by how many hydrogens or hydroxides

Question 9

what is equilibrium constant for water

Answer 9

Kw

Question 10

what is Kw

Answer 10

(1.00 x 10-14)

Question 11

what is Kw formula

Answer 11

Kw (1.00 x 10-14) = [H+] [OH-]

Question 12

what is the only factor that affects Kw

Answer 12

• Only factor that affects Kw is temperature

o As temperature rises, so does Kw

Question 13

When is a substance basic (Kw)

Answer 13

• When [H+] < [OH-], or < 1.00 x 10-7 = Basic

Question 14

when is a substance acidic (Kw)

Answer 14

• When [H+] > [OH-], or > 1.00 x 10-7 = Acidic

Question 15

How to find OH when given H concentration

Answer 15

H/Kw

Question 16

How to find H when given OH concentration

Answer 16

OH/Kw

Question 17

How to find pH of a strong acid

Answer 17

1. Find concentration of H+ (=molarity/concentration of substance in relation to moles e.g. H2SO4= 2x concentration)
2. pH= -log 10 [H3O+]

Question 18

how to find pH of strong base

Answer 18

1. Find concentration of OH+ (=molarity/concentration of substance in relation to moles e.g. Mg(OH)2= 2x concentration)
2. Find H through Kw (1.00 x 10-14) = [H+] [OH-]
3. pH= -log 10 [H3O+]

Question 19

Formula for adding two strong acid and base

Answer 19

1. Write balanced equation
2. Calculate moles in both the acid and base (n=c x v)
3. If solution neutral, then [H+] = [OH-] // determine which is in excess and by how much
4. Calculate [H+] using C= n/V (Volume= addition of amount of acid and base added)
5. Calculate pH using pH= -log 10 [H3O+]

Question 20

What is Ka

Answer 20

• Acid dissociation equilibrium constant (Ka)
  o Ka represents a weak acid in an aqueous solution
  ♣ Don’t include water as its concentration does not alter significantly

Question 21

what is a large ka and small ka

Answer 21

♣ Large Ka = strong acid completely ionises

♣ Small Ka = weak acid

Question 22

what are the two assumptions for Ka

Answer 22

1. At equilibrium [HA] is same as the initial concentration; weak acid only ionises to a small degree
2. [H3O+] produced by the self-ionisation of water is negligible and has no effect on calculations

Question 23

what is the formula for Ka

Answer 23

Ka= [H3o]2 /[HA]

Question 24

Formala for percentage ionisation

Answer 24

[A-]/[HA] x100

Question 25

what are the steps for finding percentage ionisation

Answer 25

1. Find hydronium concentration= A-
2. Determine original acid concentration
3. Place in formula