Ch 4- Acids and Bases Flashcards
Arrhenius acid
substance that produces H+ ions in water
Arrhenius base
substance that produces OH- ions in water
Bronsted-Lowry acid
proton donor
Bronsted-Lowry base
proton acceptor
conjugate base
the species formed when an acid transfers a proton to a base
conjugate acid
the species formed when a base accepts a proton from an acid
carbocation
a species in which one of the carbons has only six electrons in its valence shell and has a charge of +1
What is the equilibrium expression?
K_eq = [H3O+][A-] / [HA][H2O]
acid dissociation constant
equal to the equilibrium constant K_eq for an acid dissociation reaction multiplied by the concentration of water
What is pKa equal to?
pKa= -log Ka
The larger the value of pKa, the weaker the _____.
acid
The smaller the value of pKa, the stronger the _____.
acid
The weaker the acid, the stronger its _____.
conjugate base
The stronger the acid, the weaker its ______.
conjugate base
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 _____ and indicate _____.
greater than 1; that the majority of molecules of the acid are dissociated in water
Positive pKa values correlate to acids with equilibrium constants _____ and indicate _____.
less than 1; that most acid molecules remain undissociated in water
Each single unit increase between pKa values represents _____.
a tenfold increase or decrease in the strength of the acids being compared
In an acid-base reaction, the position of equilibrium always favors _____.
reaction of the stronger acid and stronger base to form the weaker acid and weaker base; thus, at equilibrium, the major species present are the weaker acid and weaker base
reaction mechanism
a step-by-step description of how a chemical reaction occurs
thermochemistry
the study of the energy of chemical structures
During collisions, the kinetic energy of the reactants is converted into ______ which is stored in _____.
potential energy; the chemical structures in the form of the structural strains, and the energy is released as the molecules again adopt their optimal geometries
transition state
the highest energy point on a reaction coordinate diagram; AKA activated complex
reaction coordinate diagram
a graph showing the energy changes that occur during a chemical reaction; energy is on the y-axis and reaction progress is on the x-axis
Wells on a reaction coordinate diagram represent _____.
stable structures that have lifetimes
Points along a reaction coordinate diagram that are not a part of a well represent _____.
unstable structures that cannot be isolated
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 products
thermodynamics
the study of the relative energies between any 2 entities on a reaction coordinate diagram that are shown in wells
Gibbs free energy change
the energy that dictates the position of chemical equilibria and rates of chemical reactions
If the Gibbs free energy is < 0, then _____ are favored.
products
If the Gibbs free energy is > 0, then _____ are favored.
reactants
Equation for Gibbs free energy
ΔGo = -RTlnK_eq
Gibbs free energy of activation
the Gibbs free energy difference between the reactants and the transition state; controls the rate of the reaction and the ability of the reactants to achieve the transition state
Transition states are higher in energy than _____, so ΔG‡ is always _____.
reactants; positive
exergonic reaction
a reaction in which the Gibbs free energy of the products is lower than that of the reactants; the position of equilibrium favors products
endergonic reaction
a reaction in which the Gibbs free energy of the products is higher than that of the reactants; the position of equilibrium favors reactants
enthalpy change
the difference in total bond strengths and solvation between various points under comparison on a reaction coordinate diagram
heat of reaction
the difference in the enthalpy between the reactants and the products
exothermic reaction
a reaction in which the enthalpy of the products is lower than the enthalpy of the reactants; heat is released
endothermic reaction
a reaction in which the enthalpy of the products is higher than the enthalpy of the reactants; heat is abosrbed
