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
a reaction mechanism describes which bonds are … and which are …, as well as the … and … of the various bond-breaking and bond-forming steps
broken; formed; order; relative rates
most chemical reactions occur via
collisions
the velocity at which the molecules move through the vessel is proportional to their …
kinetic energy
higher-energy collisions occur between molecules possessing larger … During collision, the structures of the molecule … and …, and collisions of higher energy lead to larger … in structure
kinetic energy; contort; flex; distortions
at higher temperatures, the energy of the collisions is greater because the molecules are moving more …
rapidly
reactions that result by virtue of the kinetic energy put into a reaction vessel due to temperature are called
thermal reactions
during collisions, the kinetic energy of the reactants is converted into …, which is stored in the chemical structures in the form of the …, and the energy is released as the molecules again adopt their …
potential energy; structural strains; optimal geometries
if molecules collide with enough force, bonds will … some collisions cause distortions that lead to … of bonds
break; rearrangements
during a collision process that yields a reaction, a structure forms that is called the …, also commonly called the … It has a particular geometry possessing … and … bonds, and it is so … that it transitions to .. that are less ..
transition state; activated complex; partially broken; partially formed; strained; new structures; strained
chemists use reaction coordinate diagrams to show the … for molecules involved in a chemical reaction
reaction coordinate diagrams
the transition state exists at the … point on a reaction coordinate diagram and they last less than one picosecond
highest energy
bond breaking in the reactants and bond formation in the products occur … upon collision
simultaneously
every point along the reaction coordinate that is not a reactant or product represents a chemical structure that has characteristics of …
both the reactants and the products
thermodynamics is the study of the relative energies between any two entities on a reaction coordinate diagram that are shown in
wells
gibbs free energy has a naught superscript which indicates standard states of … K and … atm
298; 1
change in Gibbs free energy =
-RTlnKeq
A negative change in G. free energy is … while a positive value is
favorable; unfavorable
when change in Gibbs is greater than 0, Keq is … (…), and when it is equal to 0, Keq = …; and when it is less than 0, Keq is … (…)
less than 1; unfavorable; 1; greater than 1; favorable
change in Gibss is a function of the change in two terms: … and …
deltaGnaught = …
entropy; enthalpy; change in enthalpy - T*change in entropy
enthalpy is the energy contained in … and ..
chemical bonds; solvation
the difference in enthalpy between reactants and products is called the …
heat of reaction
if the bonds formed in the products are stronger than the bonds in the reactant, heat will be …, the solution will warm, and the reaction is called …
released; exothermic
if the bonds formed in the products are weaker, heat will be absorbed from the solution so that it cools and ther eaction is
endothermic
enthalpy reflects the intrinsic … of the chemical structures involvedi n the reaction
stability
structures that have stronger bonds and/or that are better solvated are more … and thereby have lower …
stable; enthalpy
entropy measures … versus …, and … is favorable
disorder; order; disorder
all systems become more stable as the number of freely moving particles … and the chaotic movement of the partic lces …
increases; increases
a favorable change in entropy is defined as a … value and represents an increase in …, whereas an increase in order is reflected by a … value
positive; disorder; negative
for an acid to transfer its proton to a base, the two entities must … with a specific geometry. the trajectory of the base must be toward the … of H-A
collide; H
the lowest energy pathway for passing the proton from the acid to the base is a … approach
linear
(how to stabilize A-)
- having the negative charge on a more … atom
- having the negative charge on a … atom
- … the negative charge as described by …
- … the negative charge onto electron-withdrawing groups by the …
- having the negative charge in an orbital with more …
electronegative; larger; delocalizing; resonance contributing structures; spreading; inductive effect; s character
the relative acidity within a period of the Periodic table is related to the … of the atom in the anion that bears the negative charge. the greater it is, the more … its electrons are held, and the more … the anion is
electronegativity; strongly; stable
the relative acidity of hydrogen acids within a group is related to the … of the atom bearing the negative charge. the negative charge is … in a larger atom, so its mroe stable
size; spread over a larger volume
inductive effect: the … of e- density of a covalent bond caused by the .. of a nearby atom
polarization; electronegativity
electrons in an s orbital are … in energy than those in a p orbital and are thus held more … to the nucleus. thus, the more s character in a hybrid orbital, the more … the atom and the more … a hydrogen bonded to it
lower; tightly; electronegative; acidic
of the three types of compounds, the carbon in an … is the most electronegative (it has the most s character, of 50%)
alkyne
lewis acid: accepts a pair of … in forming the new … and acquires a … formal charge (these are …)
electrons; covalent bond; negative; electrophiles
lewis base: donates the pair of electrons and aquires a … formal charge (these are …)
positive; nucleophiles
donating an electron pair means that it becomes … to form a …
shared; covalent bond
if both reactants are equally but oppositely charged, a lewis acid-lewis base reaction result in the formation of a new covalent bond in which the product has no
charge
All bronsted-lowry acids are … acids, Lewis acids may be … or …
protic; protic; aprotic
