Chapter 2 Flashcards
Define Arrhenius acid-base chemistry
aqueous only proton (H+) transfer only
Define Bronsted-Lowry acid-base chemistry
aqueous or organic proton (H+) transfer
Define Lewis acid-base chemistry
aqueous or organic electron pair donation and acceptance
A BL acid acts as the _______________ and becomes the _____________________. The BL acid _______ the proton
proton donor
conjugate base
loses
A BL base acts as the ___________ and becomes the ___________________. The BL base ________ the proton.
proton acceptor
conjugate acid
gains
What is the purpose of the curved arrow in BL acid-base reactions?
to show the flow of electrons that occurs in the transfer of a proton.
What directions do the curved arrows in a BL acid-base reaction point?
From the electron pair on the acceptor (base) used to form the new X-H bond towards the H being used in the bond (on the acid).
From the bond initially holding the H to the adjacent atom creating an ion (as a lone pair).
Define and list the strong acids
An acid that reacts almost if not fully with water to form H3O+ ions
H2SO4, HI, HBr, HNO3, HCl, HCLO4
Define and list the strong bases
A base that reacts almost if not fully with water to form OH- ions
LiOH, KOH, NaOH, Ba(OH)2
A STRONG acid has a large ______ but a small _______
Ka
pKa
a WEAK acid has a small ________ but a large _________
Ka
pKA
pKa = __________
-log(Ka)
There is an __________ relationship between the strength of an acid and the strength of its conjugate base. This means that . . .
inverse
the stronger the acid, the weaker its conjugate base
Given an acid with a small pKa value how would you rate the strength of the acid itself and its conjugate base?
acid - strong
conjugate base - weak
The equilibrium of an acid-base reaction often lies on the side of the . . . aka the side where the acid has the _______ pKa
weaker acid and the weaker base
highest
If the acid on the reactant side is stronger than the acid on the product side, the reaction lies to the __________
right (products are favored)
If the acid on the product side is stronger, the reaction lies to the __________
left (reactants are favored)
The most important factor in determining the relative acidity of an organic acid HA is the _______________________ formed when the acid transfers a proton to the base
relative stability of the anion A-
(aka the conjugate base)
When A- is more stabilized, the reaction equilibrium shifts to the direction . . . indicating a ___________ acid
producing A- and H+
stronger
What four factors are considered to determine the stability of A-?
- the electronegativity of the atom bonded to H in HA
- Resonance stability of A-
- The inductive effect
- The size and delocalization of charge in A-
___________ molecules are the more stable. Anions will see a _______ in e- density to stabilize while cations will see an __________ in e- density to stabilize
neutral
decrease
increase
The greater the electronegativity of the atom A bearing the negative charge, the more strongly its e- are held. Therefore . . .
The stronger the electronegativity of A in A-H, the more stable the anion A- and the greater the acidity of the acid
Resonance delocalization of the charge on A- __________. Therefore, the greater the resonance stabilization of the anion . . .
stabilizes A-
the more acidic the compound
Inductive polarization of e- density is transmitted through covalent bonds of nearby atoms of __________ electronegativity
Higher
The inductive effect _________ anion A-‘s electron density thus __________ A-
reduces
stabilizing
The larger the volume over which the charge on an ion is delocalized, the _________ the stability
greater
Explain why HI is the strongest acid using the effect of A- size on ion stability
HI is the strongest acid because the negative charge on the conjugate I- is delocalized over a much larger volume than Br-, Cl-, and F-
Rank the stability factors from most (1) to least important (4)
- Resonance stability of A-
- The size delocalizing the charge of A-
- The inductive effect
- Electronegativity of atoms bonded directly to A-
In halide ions (F⁻, Cl⁻, Br⁻, I⁻), the negative charge is ___________, so a larger radius allows for better charge dispersion, making . . .
directly placed on the atom
I⁻ more stable than F due to its large atomic radius
When the negative charge is NOT placed directly on F⁻, Cl⁻, Br⁻, I⁻, which atom creates a more stable A-?
F⁻ more stable than I⁻ due to its large electronegative; F⁻ can draw the negative charge away
A Lewis acid is defined as any molecule or ion that can form a new covalent bond by ___________ a pair of electrons; a Lewis base ___________ the pair of e-
accepting
donates
Given Lewis acid A and Lewis base B with 2 lone pairs, what direction would the curved arrow aim? What is the resulting molecule?
Rarely you might encounter a Lewis acid being a carbocation in which . . .
an organic carbon is bonded to only three atoms and bears a positive formal charge allowing it to form another covalent bond with donated e- from a Lewis base
