Chapter 20: Acids, Bases, and pH

Question 1

what do acids do?

Answer 1

dissociate from H+ ions in aqueous solution

Question 2

what do alkaline do?

Answer 2

dissociate OH- ions in aqueous solution

Question 3

what is a Bronsted-Lowry acid

Answer 3

proton (H+) donor

Question 4

what is a Bronsted-Lowry base

Answer 4

proton )H+) acceptor

Question 5

what is a conjugate acid-base pair

Answer 5

two chemical species that can be interconverted

Question 6

In a conjugate acid-base pair which is the conjugate base and the conjugate acid

Answer 6

conjugate base is the species that accepts the H+

conjugate acid is the species that accepts the H+

Question 7

what does dissociation in aqueous solution require

Answer 7

presence of water

Question 8

what is H3O+ (three possible names)

Answer 8

hydronoium ion
oxonium ion
hydroxonium ion

Question 9

what does amphoteric mean and give an example of an amphoteric species

Answer 9

can act as an acid and a base depending on what it reacts with
example is water

Question 10

what happens when strong acids react with weak acids and why

Answer 10

stronger acids donate H+ because they fully dissociate

Question 11

what does monoprotic/monobasic mean

Answer 11

the substance can donate/accept one H+ per molecule

Question 12

how would you reference a substance that can donate/accept more than one proton per molecule

Answer 12

diprotic/dibasic for two

triprotic/tribasic for three

Question 13

what is pH

Answer 13

measurement of concentration of H+ in solution

Question 14

give an overview of each pH
pH<7
pH=7
pH>7

Answer 14

pH<7 increasingly acidic
pH=7 neutral
pH>7 increasingly basic/alkaline

Question 15

what is the pH equation

Answer 15

pH = -log[H+]

Question 16

what is the rearranged pH equation to give [H+]

Answer 16

[H+] = 10^-pH

Question 17

give the four general acid reaction word equations

Answer 17

acid + metal –> salt + hydrogen
acid + carbonate –> salt + water + carbon dioxide
acid + base –> salt + water
acid + alkali –> salt + water

Question 18

what do weak acids do

Answer 18

partially dissociate

Question 19

what is the special equilibrium for weak acids

Answer 19

acid dissociation constant Ka

Question 20

what is the general equation for weak acids

Answer 20

HA(aq) H+(aq) + A-(aq)

Question 21

what is the Ka equation

Answer 21

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

Question 22

what can cause Ka to change (if reaction uses same reactants)

Answer 22

the value can only change due to changes in temperature

Question 23

what does the Ka value tell you

Answer 23

greater the value of Ka the further to the right the equilibrium is
the lower the value the further to the left the equilibrium is

Question 24

what is the problem with Ka and what is the solution

Answer 24

value can be extremely big or small so use pKa instead

Question 25

what is pKa and the pKa equation

Answer 25

log function of Ka

pKa = -logKa

Question 26

what are the two approximations for simplifying Ka

Answer 26

1 [H+] = [A-]

2 [HA]eqm = [HA]start

Question 27

what is the simplified Ka equation after the approximation are made

Answer 27

Ka = [H+]^2 / [HA]start

Question 28

what are the problems with each approximation

Answer 28

1 If [H+] becomes siginificant [H=] cant equal [A-] so breaks down for very weak acids (pH>6) or dilute solutions

2 assumes negligible dissociation of acid which is not possible for dilute solutions or far stronger weak acids

Question 29

what is the special equilibrium for water

Answer 29

ionic product of water

Kw

Question 30

what is the general Kw equation

Answer 30

Kw = [H+] x [OH-]

Question 31

when is Kw constant and what is its value at this point

Answer 31

constant @ 298K (25C)

Kw = 1 x 10^-14

Question 32

Use ratio of [H+] : [OH-] to define acidic, neutral and alkaline

Answer 32

acidic [H+] > [OH-]
neutral [H+] = [OH-]
alkaline [H+] < [OH-]