Ch 4- Acids and Bases

Question 1

Arrhenius acid

Answer 1

substance that produces H+ ions in water

Question 2

Arrhenius base

Answer 2

substance that produces OH- ions in water

Question 3

Bronsted-Lowry acid

Answer 3

proton donor

Question 4

Bronsted-Lowry base

Answer 4

proton acceptor

Question 5

conjugate base

Answer 5

the species formed when an acid transfers a proton to a base

Question 6

conjugate acid

Answer 6

the species formed when a base accepts a proton from an acid

Question 7

carbocation

Answer 7

a species in which one of the carbons has only six electrons in its valence shell and has a charge of +1

Question 8

What is the equilibrium expression?

Answer 8

K_eq = [H3O+][A-] / [HA][H2O]

Question 9

acid dissociation constant

Answer 9

equal to the equilibrium constant K_eq for an acid dissociation reaction multiplied by the concentration of water

Question 10

What is pKa equal to?

Answer 10

pKa= -log Ka

Question 11

The larger the value of pKa, the weaker the _____.

Answer 11

acid

Question 12

The smaller the value of pKa, the stronger the _____.

Answer 12

acid

Question 13

The weaker the acid, the stronger its _____.

Answer 13

conjugate base

Question 14

The stronger the acid, the weaker its ______.

Answer 14

conjugate base

Question 15

If the pKa of an acid is near zero, then the equilibrium constant for the reaction of that acid protonating water is _____.

Answer 15

near 1

Question 16

Negative pKa values correlate to acids with equilibrium constants _____ and indicate _____.

Answer 16

greater than 1; that the majority of molecules of the acid are dissociated in water

Question 17

Positive pKa values correlate to acids with equilibrium constants _____ and indicate _____.

Answer 17

less than 1; that most acid molecules remain undissociated in water

Question 18

Each single unit increase between pKa values represents _____.

Answer 18

a tenfold increase or decrease in the strength of the acids being compared

Question 19

In an acid-base reaction, the position of equilibrium always favors _____.

Answer 19

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

Question 20

reaction mechanism

Answer 20

a step-by-step description of how a chemical reaction occurs

Question 21

thermochemistry

Answer 21

the study of the energy of chemical structures

Question 22

During collisions, the kinetic energy of the reactants is converted into ______ which is stored in _____.

Answer 22

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

Question 23

transition state

Answer 23

the highest energy point on a reaction coordinate diagram; AKA activated complex

Question 24

reaction coordinate diagram

Answer 24

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

Question 25

Wells on a reaction coordinate diagram represent _____.

Answer 25

stable structures that have lifetimes

Question 26

Points along a reaction coordinate diagram that are not a part of a well represent _____.

Answer 26

unstable structures that cannot be isolated

Question 27

Every point along the reaction coordinate that is not a reactant or product represents _____.

Answer 27

a chemical structure that has characteristics of both the reactants and products

Question 28

thermodynamics

Answer 28

the study of the relative energies between any 2 entities on a reaction coordinate diagram that are shown in wells

Question 29

Gibbs free energy change

Answer 29

the energy that dictates the position of chemical equilibria and rates of chemical reactions

Question 30

If the Gibbs free energy is < 0, then _____ are favored.

Answer 30

products

Question 31

If the Gibbs free energy is > 0, then _____ are favored.

Answer 31

reactants

Question 32

Equation for Gibbs free energy

Answer 32

ΔGo = -RTlnK_eq

Question 33

Gibbs free energy of activation

Answer 33

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

Question 34

Transition states are higher in energy than _____, so ΔG‡ is always _____.

Answer 34

reactants; positive

Question 35

exergonic reaction

Answer 35

a reaction in which the Gibbs free energy of the products is lower than that of the reactants; the position of equilibrium favors products

Question 36

endergonic reaction

Answer 36

a reaction in which the Gibbs free energy of the products is higher than that of the reactants; the position of equilibrium favors reactants

Question 37

enthalpy change

Answer 37

the difference in total bond strengths and solvation between various points under comparison on a reaction coordinate diagram

Question 38

heat of reaction

Answer 38

the difference in the enthalpy between the reactants and the products

Question 39

exothermic reaction

Answer 39

a reaction in which the enthalpy of the products is lower than the enthalpy of the reactants; heat is released

Question 40

endothermic reaction

Answer 40

a reaction in which the enthalpy of the products is higher than the enthalpy of the reactants; heat is abosrbed