Topic 18 - Acids / Bases

Question 1

Arrhenius acid definition

Answer 1

Substance with covalently bonded H atoms and dissociates in H2O to yield H3O+

Question 2

Arrhenius base definition

Answer 2

Substances with OH in its formula that dissociates in H2O to yield OH

Question 3

Arrehenius Acid-Base Reaction

Answer 3

Neutralization
a) Exothermic (-55.9 kJ mol-)
b) Formation of H2O (l) and salt

Question 4

Strength of an acid / base

Answer 4

Extent of dissociation to produce [H+] and [OH−] in solution

Question 5

Strong acid / base

Answer 5

Fully dissociate in solution (~100%)

Question 6

Weak acid / base

Answer 6

Partially dissociate in solution (<5%)

Question 7

Substances that behave as strong acids

Answer 7

HNO3
HCl
HBr
HI
H2SO4
HClO3
HClO4

Question 8

Substances that behave as weak acids

Answer 8

a) HF
b) Oxoacids (# O atoms = > ionizable H+)
c) H is not bonded to O or to a halogen
d) Carboxylic acids (ROOCH)

Question 9

Substances that behave as strong bases

Answer 9

Water soluble compounds containing OH- or O2-
a) G1
b) G2 (except Mg)

Question 10

Substances that behave as weak bases

Answer 10

a) Those with an e- rich N atoms (Ammonia / Amines)
b) Anions of weak acids

Question 11

Acid dissociation constant (Ka)

Answer 11

Measures the extent of acid dissociation in water

Question 12

Water Autoionization Formula

Answer 12

2H2O(l)⇌H3O+(𝑎𝑞 )+OH−(𝑎𝑞 )

Question 13

Reasons for Water Autoionization

Answer 13

Amphoteric nature of H2O

Question 14

Ion-product constant of H2O (at 298K)

Answer 14

Kw = [H+][OH−] = 1.0×10−14

Question 15

Relationship between H3O+ and OH-

Answer 15

Inversely proportional
a) As the concentration of one of these ions increases, the concentration of the other must decrease

Question 16

When is a solution…?
a) Neutral
b) Basic
c) Acidic

Answer 16

a) H+ = OH-
b) H+ < OH-
c) H+ > OH-

Question 17

pH

Answer 17

-log([H+])

Question 18

Number of significant figures inside the logarithm should equal…

Answer 18

the number of decimal places in the number

Question 19

pH + pOH = … (at 298K)

Answer 19

14

Question 20

How is pH measured?

Answer 20

a) Acid-base indicators. Organic molecules where color depends on the solution’s acidity
b) pH meter (Probe with 2 electrodes)

Question 21

Bronsted-Lowry acid definition

Answer 21

Proton donor

Question 22

Bronsted-Lowry base definition

Answer 22

Proton acceptor containing a lone pair of e-

Question 23

Brønsted-Lowry Acid-Base Reaction

Answer 23

Proton transfer process that can occur between gases, nonaqueous solutions, and heterogeneous mixture

Question 24

Conjugate acid-base pairs

Answer 24

Two species which differ by H+
a) Acid becomes into the conjugate base
b) Base becomes into the conjugate acid

Question 25

Relationship between the strength of a conjugate acid and a conjugate base

Answer 25

The weaker the acid/base, the stronger the conjugate base/acid

Question 26

Amphiprotic definition

Answer 26

Substance capable of accepting and donating H+

Question 27

A reaction proceeds to the greater extent in the direction in which...

Answer 27

a stronger acid and stronger base form a weaker acid and weaker base

Question 28

Assumptions of weak-acid equilibria problems

Answer 28

a) [H3O+] from the autoionization of H2O is negligible b) A weak acid has a small Ka, so we can neglect the change in its concentration to find its equilibrium concentration

Question 29

% Acid dissociation formula

Answer 29

([HA]dis / [HA]i)*100

Question 30

Why does Ka of successive ions differ by several orders of magnitude?

Answer 30

It is more difficult for the positively charged H+ ion to leave a singly charged anion than to leave a neutral molecule

Question 31

Factors affecting the acid strength of nonmetal hydrides

Answer 31

a) Electronegativity of central nonmetal b) Strength of the EH bond

Question 32

Polyprotic Acids

Answer 32

Acids with more than one ionizable H+

Question 33

Trends of the acid strength of nonmetal hydrides

Answer 33

a) Across a period: Increasess b) Down a group: Increases

Question 34

Factors affecting the acid strength of oxoacids

Answer 34

a) Electronegativity of central nonmetal b) # O atoms around central nonmetals

Question 35

Effect of concentration on the extent of acid dissociation

Answer 35

As the initial acid concentration decreases, the percent dissociation of the acid increases

Question 36

Trends of the acid strength of nonmetal hydrides

Answer 36

a) Acid strength increases with the electronegativity of nonmetal b) Acid strength increases with # of O atoms

Question 37

Reasons for the acidity of hydrated metal ions

Answer 37

Small and highly charged, which withdraws sufficient e- density from OH bonds of the bound water molecules for an H+ to be released

Question 38

Relationship between Ka and Kb of a Conjugate Acid-Base Pair

Answer 38

(Ka)*(Kb) = Kw

Question 39

Acidity of a salt from strong acid and strong base

Answer 39

Neutral (NaCl)

Question 40

Acidity of a salt from strong acid and weak base

Answer 40

Acidic NH4+ + H2O ↔ NH3 + H3O+

Question 41

Acidity of a charged metal cation and anion of strong acid

Answer 41

Acidic Al(H2O)63+ + H2O ↔ Al(H2O)5OH2+ + H3O+

Question 42

Acidity of a salt from strong base and weak acid

Answer 42

Basic NO2− + H2O ↔ HNO2 + OH−

Question 43

Acidity of salts of amphiprotic anions or anions from weak acids / cations from basic cations

Answer 43

Depends on Ka and Kb

Question 44

Leveling Effect of Water

Answer 44

An acid yields the cation and a base yields the anion that would be produced by autoionization of the solvent.

Question 45

Why are all strong acids and strong bases equally strong in water?

Answer 45

In water, the strongest acid possible is H3O+ and the strongest base possible is OH−:

Question 46

Method used to rank the relative strength of strong acids

Answer 46

Dissolve them in a solvent that is a weaker base than water, so it accepts their protons less readily

Question 47

Lewis acid definition

Answer 47

Species that can accept a pair of electrons

Question 48

Lewis base definition

Answer 48

Species that can donate a pair of electrons

Question 49

Examples of Lewis Acid compounds

Answer 49

e- deficient compounds such as B/Al Molecules with a polar double bond (e.g. SO2 / CO2) Metal ion in complex ions

Question 50

Lewis-acid base reaction

Answer 50

Donance and acceptance of an e- pair to form an adduct, a single species that contains a new covalent bond