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Blocco d > Acid And Base > Flashcards

Acid And Base Flashcards

1
Q

Explain why aqueous complex are acidic as follows
Fe2+<Fe3+<Al3+~Hg2+

A

Acidity increases with smaller dimensions and higher charges. Hg is a special case because it covalently bonds O as it transfers positive charge to it

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2
Q

KI(aq) is acid, base or neutral

A

Neutral

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3
Q

Mg(ClO4)2(aq) is acid, base or neutral

A

Acidic

Mg²+ + 6H2O= [Mg(H2O)6]²+
[Mg(H2O)6]²+ + H2O = [Mg(H2O)5(OH)]+ + H3O+

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4
Q

NaHS(aq) is acid, base or neutral

A

Basic

HS- + H2O = H2S + OH-

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5
Q

Arrange aqueous complex in order of acidity

Na+
Sc3+
Mn2+
Ni2+

A

Na
Mn
Ni
Sc

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6
Q

Arrange aqueous complex in order of acidity

Fe3+
Na+
Mn2+
Ca2+
Al3+
Sr2+

A

Na
Sr
Ca
Mn
Fe
Al

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7
Q

Who’s more acid
H2CrO4 or HMnO4

A

HMnO4 because Mn has a higher ox state

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8
Q

Who’s more acid, aqua complex of Na+ or Ag+
Their radii is similar

A

Ag
because Ag-OH2 bond is more covalent, meaning that can delocalize the positive charge of the cation over the whole complex
OR VICEVERSA
It can delocalize the negative charge of oxygen on the metal, resulting in a more polarised OH bond

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9
Q

Why the Lewis acidity of silicon tetrahlides is
I<Br<Cl<F

A

Because it increase with increasing electronegativity and decreasing size of the halide

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10
Q

Why the Lewis acidity of boron tetrahlides is
F<Cl<Br<I

A

Going down the halogens, they become bigger and the π interaction decreases.
In other words, BF3 is stabilized by its planar geometry having the hybrids with B=F bonds

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11
Q

What’s the structure of (H3Si)3N and (H3C)3N knowing that the π bonding is important

A

The N lone pair in (H3Si)3N is delocalized onto the three Si atoms, so it cannot perform its usual repulsion.
(H3Si)3N is trigonal planar
(H3C)3N is trigonal pyramidal

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12
Q

Acidity depends on

A

The smaller the atom and the higher is their charge, the more acidic it is

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13
Q

Are Lewis acid sustances

A

-With incomplete octet of Valence electrons
-Metal cation that interact with water
-that can rearrange in order to accept another lone pair
-can expand its Valence shell

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14
Q

Who is the acid and the base

SO3 + H2O = HSO4- + H+

A

SO3 AND H+ are acid

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15
Q

Who is the acid and the base

CH3[B12] + Hg²+ = [B12]+ + CH3Hg+

A

Hg²+ and [B12] are the acid

Displacement

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16
Q

Who is the acid and the base

KCl + SnCl2 = K+ + (SnCl3)-

A

SnCl2 and K+ are acid

Displacement

17
Q

Who is the acid and the base

AsF3 + SbF5 = [AsF2]+[SbF6]-

A

SbF5 and AsF2+ ARE ACID

DISPLACEMENT

18
Q

Who is the acid and the base

EtOH + Py = non conducting sol

A

EtOH is the acid

Lewis acid-base complex

19
Q

Why (H3Si)2O is less basic than (H3C)2O

A

Si can expand its Valence shell by delocalization of O lone pairs to create multiple bonds

20
Q

Why (H3Si)2N is less basic than (H3C)2N

A

Si can expand its Valence shell by delocalization of N lone pairs to create multiple bonds

21
Q

Who’s the strongest Lewis acid
BF3
BCl3
BBr3

A

BBr3 because has the longest bond so the p-p π bonding is less involved

22
Q

Who’s the strongest Lewis acid
BeCl2
BCl3

A

BCl3 because the ox number of B is higher than Be

23
Q

Who’s the strongest Lewis acid
B(n-bu)3
B(t-bu)3

A

n-bu because has less steric repulsions with the Lewis base

24
Q

Who’s more basic towards B(CH3)3
Me3N
Et3N

A

NMe3 because is less hindered

25
Q

Who’s more basic towards B(CH3)3
2-Me-py
4-Me-py

A

4-Me-py because the methyl in para affect less sterically the B-N bond

26
Q

CsF + BrF3 =

A

Cs+ + BrF4-

27
Q

ClF3 + SbF5 =

A

ClF2+ + SbF6-

28
Q

B(OH)3 + H2O =

A

[B(OH3)(H2O] -> [B(OH)4]- + H+

29
Q

B2H6 + 2PMe3 =

A

2[BH3(PMe3)]

30
Q

SiO2 + 4HF =

Interpret it as bronsted and Lewis acid base

A

SiF4 + 2 H2O

Bronsted: transfer of proton from HF to O²-
Lewis: formation of Si(IV) complex with F-

31
Q

Who’s a molecule with incomplete octet which can accept an electron pair to complete its Valence shell?

A

BF3 with NH3

32
Q

Who is a metal cation that can accept an electron pair by a base?

A

M²+ with H2O giving aquo complex

33
Q

Who can rearrange its complete octect in order to accept another electron pair

A

CO2 with OH- giving the bicarbonate ion HCO3-

34
Q

Who can expand its Valence shell to accept another electron pair

A

SiX4 + 2X- to give (SiX6)²-

35
Q

Explain the thermodynamic stability of NH3->BX3

A

BX3 is panar and has incomplete octets, and the vacant p orbital perpendicular to the plane can accept a lone pair from a Lewis base such as NH3 to give Lewis adducts NH3->BX3.

The X atoms in BX3 form p bonds with the empty B2p orbital, and these p bonds must be disrupted to make the acceptor orbital available for complex formation.

The p bond also favours the planar structure of the molecule, that must be converted to pyramidal in order to form in the adduct. The small F atom forms the strongest p bonds with the B2p orbital, then it is Cl atom and finally Br atom.

36
Q

What’s the application with it’s condition of BF3(g)

A

It’s used as a catalyst to generate carbocations. To used it, it is dissolved in Et2O, forming a complex with :O

37
Q

Who’s the acid

BrF3 + F- = BrF4

A

BrF3

38
Q

Who’s the base

KH + H2O = KOH + H2

A

K is a spectator, therefore H- is the base

39
Q

What’s hypervalence

A

The capability of group 14 to expand their Valence shell, acting as Lewis acid in order to become five-/six- coordinated

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