Chapter 4 Flashcards
According to the Arrhenius definition, an acid is a substance that dissolves in water to produce … A base is a substance that dissolves in water to produce …
H+ ions; OH- ions
An H+ ion immediately combines with a water molecule to give a …
hydronium ion
According to Bronsted-Lowry def, an acid is a …, a base is a …, and an acid-base reaction is a … reaction
proton donor; proton acceptor; proton-transfer reaction
any pair of molecules or ions that can be interconverted by transfer of a proton is called a
conjugate acid-base pair
when an acid transfers a proton to a base, the acid is converted to its …
conjugate base
when a base accepts a proton, it is converted to its
conjugate acid
the members of a conjugate acid-base pair differ by a
proton
for acid-base reactions, we write the Lewis structures of reactants and products, showing all valence electrons. we then use … to show the change in position of electron pairs during the reaction. the tail of the curved arrow is located at an …, either a lone pair or a bonding pair. The head of the curved arrow shows the new … of the electron pair
curved arrows; electron pair; location
a curved arrow originating at a lone pair and pointing to an adjacent atom indicates …, while an arrow originating at a bonding electron pair and pointing toward a previously bonded atom indicates a …
formation of a new bond; breaking of that bond
the more stable charged species is the one in which the charge is more …
delocalized
relative charge delocalization can often be understood by considering
resonance
we see that protonation of a carboxyl group occurs preferentially on the … oxygen because this cation has a greater … of charge
carbonyl; delocalization
proton transfer reactions also occur with compounds having … electrons
pi
the result of proton transfer reactions with pi bonds is the formation of a …., a species in which one of its carbons has only … electrons in its valence shell and carries a charge of …
carbocation; six; +1
any quantitative measure of the acidity of organic acids or bases involves measuring the … of the various components in an acid-base equilibrium. the strength of an acid is then expressed by an …
equilibrium concentrations; equilibrium constant
dissocation of the acid, …, in water gives an anion …, and the hydronium ion.
HA; A-
The general chemical equation and equilibrium constant for ionization of an acid is:
… + … (equilibrium arrows) … + …
Keq =
HA + H2O; A- + H3O+; [H3O+][A-]/[HA][[H2O]
because water is the solvent for this reaction and its concentration changes very little when HA is added to it, we can treat the concentration of water as a constant equal to …
1000 g/L
acid dissociation constant, Ka =
[H3O+][A-]/[HA]
acid strengths are often expressed as …
pKa (-log10Ka)
the larger the value of pKa, the … the acid
weaker
the smaller the value of pKa, the … the acid
stronger
the weaker the acid, the … its conjugate base
stronger
the stronger the acid, the … its conjugate base
weaker
if the pKa of an acid is near zero, then the equilibrium constant for the reaction of that acid protonating water is near
1
negative pKa values correlate to acids with equilibrium constants …, while positive pKa values are for acids with equilibrium constants …
greater than 1; less than 1
in an acid-base reaction, the position of equilibrium always favors reaction of the …. acid and … base to form the … acid and … base
stronger; stronger; weaker; weaker