Chapter 20: Acids, Bases, and pH (20.1-20.5) Flashcards

1
Q

what is a bronsted-lowry acid?

A

a H+/proton donor

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2
Q

what is a bronsted-lowry base?

A

a H+/proton acceptor

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3
Q

the general equation for acid dissociation

A

HA < – > H+ + A-

A- is the conjugate base

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4
Q

Define a conjugate acid-base pair

A

a conjugate acid-base pair contains 2 species that can be interconverted by transfer of a proton
(eg HNO3 and NO3- can be interconverted by transfer of a proton/H+ ion)

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5
Q

define monobasic acid

A

has 1 proton (H+) that can be replaced in an acid-base reaction

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6
Q

define dibasic acid

A

has 2 protons (H+) that can be replaced in an acid-base reaction

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7
Q

define tribasic acid

A

has 3 protons (H+) that can be replaced in an acid-base reaction

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8
Q

hydronium ion

A

H3O+

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9
Q

what is a salt

A

a salt is the product of a neutralisation reaction with an acid and a base where the H+ ion has been replaced with either a metal or ammonium (NH4+)

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10
Q

a strong acid

A

releases all of its H+ ions in aqueous solution
HA –> H+ + A-
example: HCl, H2SO4

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11
Q

weak acid

A

does not release all of its H+ ions in aqueous solution
HA < – > H+ + A-
example: all organic acids eg CH3COOH

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12
Q

equation for pH

A

pH = -log[H+]

use base 10

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13
Q

acid dissociation constant or Ka

A
Ka = [H+][A-] / [HA]
or  = [H+]^2 / [HA]

HA < – > H+ + A- (Ka is only for weak acids)

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14
Q

pKa =

A

-log(Ka)

base 10

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15
Q

dilute acid + metal –>

redox

A

salt + H2

eg 2H+(aq) + Zn(s) –> Zn 2+(aq) + H2(g)

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16
Q

common bases

A

carbonates, metal oxides, metal hydroxides, alkalis

17
Q

acid + carbonate –>

neutralisation

A

salt + water + CO2

eg 2H+(aq) + CaCO3(s) –> Ca 2+(aq) + H2O(l) + CO2(g)

18
Q

acid + metal oxide (s) –>
acid + metal hydroxide (s) –>
(neutralisation, they are the same)

A

salt + water

19
Q

acid + alkali –>

neutralisation

A

H2O

eg H+(aq) + OH-(aq) –> H2O (l)

20
Q

[H+] =

A

[H+] = 10^(-pH)

21
Q

larger acid dissociation (Ka) means

A

stronger acid

22
Q

a larger pKa means

A

a weaker acid (a smaller Ka)

23
Q

neutralisation is

A

a chemical reaction in which an acid and a base reacts to form water

24
Q

in strong acids: [H+] =

A

[H+] = [HA]

25
Q

weak acid:
[HA] (at equilibrium) =

And why does this not necessarily work for ‘stronger’ weak acids?

A

[HA(aq)] (start)&raquo_space; [H+(aq)] (equilibrium)
HA(aq) = [HA(aq)] (start) - [H+(aq)] (eqm)
[HA] (at eqm) ~ [HA] (at start)

Breaks down when [H+] becomes significant and there is a real difference between
[HA(aq)] (equilibrium) and [HA(aq)] (start) - [H+(aq)] (equilibrium)

26
Q

what is Kw (definition)

A

the ionic product of water
H2O dissosiates slightly, acting as a weak acid
H2O < – > H+ + OH-

27
Q

what is Kw (equation)

A

Kw = [H+] X [OH-]

you are given the value of Kw

28
Q

what is Kw (number value)

A

Kw (at rtp) = 1 X 10^-14

29
Q

if [H+] = [OH-]

A

solution is neutral

30
Q

if [H+] > [OH-]

A

solution is acidic

31
Q

if [H+] < [OH-]

A

solution is alkali

32
Q

strong bases

A

completely dissociate in aqueous solution

KOH –> K+ + OH-

33
Q

how to find the pH of a strong base

A

[KOH] = [OH-]
then use Kw = [H+][OH-] to find [H+]
use pH = -log[H+]

34
Q

Why do we use pH rather than [H+]?

A

pH makes the numbers more manageable, as it takes a log of the really small [H+] values

35
Q

Weak acid approximation for [H+] at equilibrium

A

[H+] (equilibrium) ~ [A-] (equilibrium]

i.e there is a negligible dissociation of water (weak solutions would cause there to be more H+ due to its dissociation in water)