Acids and Bases Flashcards

1
Q

What do all acids release

A

H+

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2
Q

What do all bases accept

A

H+

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3
Q

Common bases

A

Metal oxides
Metal hydroxides
Ammonia and amines

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4
Q

Alkalis (soluble bases that dissolve in water release in water

A

OH- ions

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5
Q

How are salts made

A

When H+ from acid is replaced by a metal ion/another positive ion

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6
Q

Neutralisation reactions

A
Acids react with:
carbonates to form CO2
bases (metal oxides) to form H2O
alkalis to form H2O
Metals to form H
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7
Q

Redox reactions

A

Acids react with metals
Metal is oxidised
Hydrogen is reduced

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8
Q

Ammonia

A

Forms weak alkaline solution when dissolved in H2O

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9
Q

Salt crystals features

A

Have water = crystalline form, hydrated
No water = powdered form, anhydrous
Molar proportion of H2O 名前 water of crystallisation

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10
Q

Hydrated salt formula

A

1: calculate n of anhydrous
2: calculate n of H2O
3: determine hydrated salt ormula

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11
Q

Titration calculation method

A

1) find n of compound in the sol
2) use equation to ID mol no. of substances in 2nd sol.
3) ID n for any other relevant substances
4) scale quantities to match
5) calculate M

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12
Q

Bronsted-Lowry model

A

(conjugate) Acid = H+ donor
(conjugate) Base = H+ acceptor
Alkali = base that dissolves in H2O forming OH-

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13
Q

Water’s acid-base equilibrium

A

Ha(aq) ⇌ H+(aq) + A-(aq)

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14
Q

Acid strength

A

Extent to which it dissociates into H+ and A-

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15
Q

Strong acid strength

A

Almost complete dissociation

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16
Q

Weak acid strength

A

Partial dissociation

Equilibrium favours non-dissociated side

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17
Q

Ka, acid dissociation constant

A

Dissociated side/non-dissociated side

Unit = mol dm-3

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18
Q

Large vs small Ka

A

Large Ka = large dissociation, strong acid

Small Ka = small dissociation, weak acid

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19
Q

Concentration vs strength of acid

A

Concentration = amount of acid dissolved in 1dm3 o solution

Strength=dissociation extent

20
Q

pH formula

A

pH=-log10 [H+(aq)]

21
Q

H+ formula

A

[H+(aq)]= 10-pH

22
Q

pH value meanings

A

Low H+ value = high pH value

High H+ value = low pH value

23
Q

pH changed by 1 =

A

H+ changed by 10x

24
Q

Strong acid pH calculations

A

Found directly from acid concentration

[H+]=[HA]

25
Weak acids pH calculation
Need acid concentration and Ka value Consider: [HA(aq)]equilibrium ≈ [HA(aq)]start [H+(aq)] ≈ [A-(aq)] Formula therefore: Ka ≈ [H+(aq)]2/[HA(aq)]
26
pKa and Ka link
Logarithmic version of Ka ``` pKa = -log10Ka Ka = 10-pKa ``` Low Ka = high pKa High Ka = low pKa
27
Kw
Ionic product of water Kw=[H+(aq)][OH-(aq)]
28
Kw at 25 degrees
Kw=1.0x10-14 mol2 dm-6
29
H+ and OH- in water
Same concentrations, 10-7 mol dm-3. Total therefore: 10-14 mol dm-3
30
H+ vs OH- concentrations
Water: H+ = OH- Acid: H+ > OH- Alkaline: H+ < OH- Linked by Kw
31
Strong alkalis pH calculation
1) Find concentration directly from alkali concentration 2) solve for H+ ( Kw/OH-) 3) calculate pH
32
Titration curve features
Mid-point of vertical bit is Equivalence Point | Indicator is only suitable if its pKind value is within the pH range of the vertical part
33
Ka from a titration curve
1) Get vol. of alkali for neutralisation from titearion curve 2) get pH at half-neutralisation fron curve 3) half-neut, HA = A-, so Ka = H+ Ka = 10-pH
34
∆Hneut value
Approximately -57.9kJ mol -1 for strong acids | Less exothermic for weak acids
35
Buffer soluions
Minimise pH changes by removing most of added acid/alkali Made of HA and its conjugate base
36
Adding H+ to a buffer
H+ is increased pH change is opposed. Equilib moves left removing H+ and forming HA A- removes most of added H+
37
Adding alkali to buffer
Added OH- reacts with small concentration of H+ pH change opposed by moving equil to the right, restoring H+ as HA dissociates HA restores most of lost H+
38
Buffer solution pH depends on
* Ka of buffer system | * ratio of weak acid and its conjugate base
39
Arrhenius acids and bases
Acids: dissociate in water to make H3O+ Bases: dissociate to make OH-
40
Lewis acids and bases
Acid aka electrophile: e- acceptor | Base aka nucleophile: e- donator
41
Acid-conjugate base link
Acids are directly proportional to conjugate base's stability. More stable = more acidic
42
Base stability considerations
``` Larger atoms いい More electronegative いい sp hybridised >sp2>sp3 いい e- withdrawing groups on acid いい Resonance structures いい ```
43
pKa values
V strong acids = pKa &<0 | Weak acids = pKa 0-9
44
Equilibrium rule
Equilibrium of a reaction will favour side with weaker acids and bases
45
Acid dissociation constant
Ka = [H+][A-]/[HA]
46
Buffer solution pH
pKa + log10 (salt/acid)