CHM 112 Chapter 18

A particular salt contains both an acidic cation and a basic anion. If the Ka of the cation is greater than the Kb of the anion, a solution of the salt will be ______. If the Ka of the cation is less than the Kb of the anion, a solution of the salt will be ______.

acidic; basic

The product of a Lewis acid-base reaction is called a(n) _____, which is a single species containing a new _____.

adduct; covalent bond

A Bronsted-Lowry acid is a proton _____ and must therefore contain at least one ionizable _____ atom in its formula.

donor; hydrogen

Which of the following options correctly describe the constant Ka? Select all that apply.

[H2O] is not included in the Ka expression for a particular acid. Ka is the acid-dissociation constant.

Which of the following gives the correct mathematical operation required to calculate the [H3O+] given a pH of 5.0?

[H3O+] = 10^-5.0

Which of the following statements correctly describes the behavior of strong acids, HA, in aqueous solution?

[H3O+] = [A-] ≈ [HA]init Strong acid molecules are not present in aqueous solutions. A strong acid dissociates completely into ions in water.

The higher the pH value, the _____ the [H3O+] and the _____ acidic the solution will be.

lower; less

According to the Bronsted-Lowry definition, an acid donates H+ to a base. An acid-base reaction can therefore be described as a(n) ______ transfer reaction.

proton

If you are given a pH and asked to calculate [H+], you would _______.

raise 10 to the power of the negative pH value

Correctly order the steps necessary to solve weak-acid equilibria problems. Start with the first step at the top of the list. Instructions

write define construct check

Nitrous acid, HNO2, has a Ka of 7.1 x 10-4. What is the [H3O+] in a 0.60 M solution of HNO2?

2.1 x 10^-2 M

H3AsO4 H2S HCOOH

3 2 1

H3PO4 H2CO3 CH3COOH

3 2 1

A monoprotic acid has _____ ionizable proton(s).

one

Select all the compounds in the following list that are strong bases.

NaOH CaO

KBr NH4I KCN

Neutral acidic basic

Which of the following species usually act as weak bases? Select all that apply.

PO43- CH3NH2 CH3COO-

______ metal ions are acidic in aqueous solution because their hydrated form can transfer an H+ to water.

Small, highly charged

Which of the following options correctly describe the structural characteristics of strong and weak bases? Select all that apply.

Soluble hydroxides are strong bases. Compounds that contain electron-rich N are weak bases. Amines such as CH3CH2NH2 are weak bases.

Which of the following types of substances are classified as acids only under the Lewis definition? Select all that apply.

Molecules that contain a polar multiple bond Molecules with electron deficient central atoms

A salt consisting of the anion of a _____ acid and the cation of a _____ base yields an acidic solution.

strong; weak

CH3COOH is a weaker acid than HF. This means that CH3COO- is a ______ base than F-.

stronger

Which of the following solutions of HCN will have the greatest percent dissociation?

0.00010 M Reason: The percent dissociation of a weak acid increases as the initial concentration of the acid decreases.

A 0.15 M solution of butanoic acid, CH3CH2CH2COOH, contains 1.51 x 10-3 M H3O+. What is the Ka of butanoic acid?

1.5 x 10^-5

The pH scale is a logarithmic scale, meaning that a solution with a pH of 1.00 has a concentration of hydronium (H3O+) _____ times _____ than a solution with a pH of 3.00.

100; greater

What is the pH of a 0.808 M KOBr solution if the Ka of HOBr is 2.0 × 10-9?

11.30

What is the pH of a 0.25 M solution of ethanolamine (Kb = 3.2 x 10-5)?

11.45

A salt consisting of the _____ of a strong acid and the _____ of a strong base yields a neutral solution.

anion; cation

Given the ion-product constant for water Kw = [H3O+][OH-], as the concentration of hydronium increases the concentration of hydroxide _____.

decreases

The ______ of dissociated HA molecules increases as a weak acid solution is diluted.

percent

Lewis base Lewis acid

e- pair donor e- pair acceptor

Calculate the Kb value for the acetate ion (CH3COO-) if the Ka value for acetic acid (CH3COOH) is 1.8 x 10-5.

5.6 x 10^-10

What is the Ka of an acid if a 0.500 M solution contains 1.70 x 10-4 M H3O+?

5.8 x 10^-8

Select all the statements that correctly describe the aqueous solution of a metal cation.

A metal cation can withdraw electron density from the O-H bonds of H2O molecules, releasing H+ ions. A solution containing small, highly charged metal cations will be acidic.

A(n) acid is one that dissociates only slightly in water, whereas a(n) acid dissociates completely into ions.

Blank 1: weak Blank 2: strong

Which of the following species is present in the greatest concentration in a 1.0 M solution of CH3COOH?

CH3COOH

Select ALL the strong acids from the following list.

HNO3 HBr H2SO4

Hydrogen cyanide (HCN) is a weak acid with Ka = 6.2 × 10-10. Which of the following options correctly reflect the steps required to calculate the pH of a solution containing 0.150 M KCN? Select all that apply.

Kb of CN- = 1.6 × 10-5 pH = 11.18

Metal cations act like ______ when dissolved in water. The hydrated cation is the ______.

Lewis acids; adduct

Select ALL the strong bases from the following list.

LiOH Ca(OH)2 Na2O

A Lewis acid is any species that _____ an electron pair, whereas a Lewis base is a species that _____ an electron pair.

accepts; donates

strong acid weak acid

H3O+, A- HA

acids dissociate completely in water.

Blank 1: Strong

The strength of a weak base is indicated by its -ionization constant Kb. The greater the value of Kb, the the base.

Blank 1: base Blank 2: stronger

H2S is a _____ acid than HCl because S is _____ electronegative than Cl, while HBr is a _____ acid than HCl because the H-Cl bond is shorter and has _____ strength than the H-Br bond.

weaker; less; stronger; greater Reason: For nonmetal hydrides, acid strength increases from left to right across a period and increases down a group.

Basic solutions will have a pOH than acidic solutions.

Blank 1: lower

A salt consisting of a small, highly charged metal cation and the anion of a strong acid yields a(n) _____ solution.

acidic

Which of the following species could act as EITHER an acid OR a base? Select all that apply.

H2PO4- H2O HCO3-

Which of the options given expresses the solution to the following calculation to the correct number of significant figures? pH = -log(1.12 x 10-12)

11.951 Reason: The number 1.12 has 3 significant figures, and the answer must therefore be quoted to 3 significant figures. Since pH is a logarithmic value, the digits before the decimal are not significant. The pH value of 11.951 therefore has 3 significant figures.

Calculate the Ka value for the anilium ion (C6H5NH3+) if Kb for aniline (C6H5NH2) is 4.0 x 10-10.

2.5 x 10^-5

An acid has a Ka of 1.34 × 10-6. What is the pH of a 0.509 M solution?

3.08

How does a conjugate acid differ from its conjugate base? Select all that apply.

A conjugate base may be positively charged, neutral, or negatively charged. The conjugate acid of a neutral base will have a charge of +1. The conjugate acid has one more H than its conjugate base.

Which of the following statements correctly describe the characteristics of polyprotic acids? Select all that apply.

A polyprotic acid has more than one ionizable proton. Polyprotic acids are generally weak acids. In calculations involving polyprotic acids, we generally only take into account H3O+ formed from the first dissociation.

Which of the following statements describe the behavior of strong and weak acids (general formula HA) in aqueous solution? Select all that apply.

A weak acid is a weak electrolyte. The solution of a strong acid will have extremely few to no undissociated HA molecules.

The anion of a weak acid can interact with H2O according to the balanced equilibrium equation: A- (aq) + H2O (aq) ⇌ HA (aq) + OH- (aq). Select all the statements that correctly describe this system.

A- is a weaker base than OH-, and the equilibrium will lie to the left. The [HA] in solution will be relatively low. The pH of this solution will be greater than 7.

Which of the following statements does NOT describe a type of weak acid?

All hydrohalic acids in Period 3 or below

Rank the three different definitions for acids and bases from the least to the most inclusive. Place the least inclusive definition at the top of the list and the most inclusive definition at the bottom of the list.

Arrhenius Bronsted-Lowry Lewis

Which of the following statements correctly describe the relationship between the species in the reaction shown? Select all that apply.

B and D are a conjugate acid-base pair. The base in the forward reaction is CH3NH2. HSO3- is the conjugate acid of SO32-.

Which of the following species are Lewis acids? Select all that apply.

BF3 Cu2+ SO3

A species that contains one or more atoms as well as one or more electron pairs can act as either an acid or a base, depending on the reaction. Such a species is described as being .

Blank 1: H or hydrogen Blank 2: lone, nonbonded, unbonded, non-bonded, or unshared Blank 3: amphoteric or amphiprotic

All strong acids and bases appear equally strong in H2O. This is because in water the strongest acid possible is , while the strongest base possible is . In both cases the equilibrium favors the dissociation products, and water is said to exert a effect on any strong acid or base.

Blank 1: H3O+, hydronium, hydronium ion, or H+ Blank 2: OH-, hydroxide, hydroxide ion, or HO- Blank 3: leveling or levelling

In order to determine the overall acidity of a 0.1 M solution of NaHCO3, the and values for HCO3- must be compared. Ignore the use of any superscripts or subscripts in your answers.

Blank 1: Ka, acid-dissociation constant, acid dissociation constant, or pKa Blank 2: Kb, base-dissociation constant, base dissociation constant, or pKb

The two general types of weak base include molecules that contain one or more atoms and the conjugate bases of weak .

Blank 1: N, nitrogen, electron rich, or electron-rich Blank 2: acids

A Bronsted-Lowry base is a proton . A Bronsted-Lowry base must contain an available pair of in its formula in order to form a(n) bond to H+.

Blank 1: acceptor Blank 2: lone , nonbonded, nonbonding, non-bonding, non-bonded, unshared, or unbonded Blank 3: electrons Blank 4: covalent or sigma

The product of a Lewis acid-base reaction is called a(n) , which is a single species containing a new bond.

Blank 1: adduct, Lewis adduct, or adduct compound Blank 2: covalent, coordinate covalent, or dative covalent

An acid donates a proton to form its conjugate , which therefore has one less atom and one more charge than its acid.

Blank 1: base Blank 2: H or hydrogen Blank 3: negative or minus

In a Bronsted-Lowry acid-base reaction, the acid reacts to form its and the base will form its .

Blank 1: conjugate Blank 2: base Blank 3: conjugate Blank 4: acid

An acid can be defined as a substance that loses one or more H+ ions when dissolved in water. An H+ ion is a hydrogen atom that has lost a(n) and is therefore just a(n) . The H+ ion is not an isolated ion, but interacts strongly with H2O to produce the ion, which has the formula H3O+.

Blank 1: electron Blank 2: proton, hydron, or cation Blank 3: hydronium or H3O+

The reaction of an acid and a base in aqueous solution, in which all H+ ions from the acid react with all the OH- ions from the base is called .

Blank 1: neutralization

A monoprotic acid has ionizable proton(s), whereas a diprotic acid has ionizable proton(s).

Blank 1: one or 1 Blank 2: two or 2

The quantity -log[H3O+] is called the of a solution.

Blank 1: pH or pH value

An acid-base reaction occurs when one species loses a proton and another species simultaneously gains a proton. An acid-base reaction can therefore be viewed as a proton- process.

Blank 1: transfer, exchange, or exchanging

Which of the following statements correctly describe the acid-base properties of a 0.10 M solution of ammonium cyanide (NH4CN)? Select all that apply. Ka of NH4+ = 5.6 x 10-10 and Kb of CN- = 1.8 x 10-5.

CN- will behave as a base when it reacts with water. The solution will be basic. Both NH4+ and CN- will hydrolyze (react with water) in aqueous solution.

Which of the following anions will produce a neutral solution in water? Select all that apply, and assume that any associated cations do not affect the pH.

Cl- I- NO3-

Finding the pH of a weak base solution is very similar to that for a weak acid. What is the only step that is necessary in the calculation of pH of a weak base and not a weak acid?

Convert [OH-] to [H3O+].

Which of the protons depicted in the structure of acetic acid is considered acidic or ionizable?

D Reason: In carboxylic acids, the ionizable proton is the one bonded to oxygen. Hydrogen atoms bonded to carbon do not ionize.

True or false: For any acid-base reaction, Ka x Kb = Kw for the reacting acid and base.

False

Which of the following choices correctly depicts the net ionic equation for the reaction of a strong acid (HNO3) with a strong base (KOH)?

H+ (aq) + OH- (aq) → H2O (l)

Which of the following formulas can be used to represent the proton ion in aqueous solution? Select all that apply.

H+(aq) H3O+(aq)

Arrange the following compounds in order of increasing acid strength (weakest at the top to strongest at the bottom of the list). Instructions

H2) HF HBr

Which of the following is NOT a conjugate acid-base pair?

H2PO4-/PO43-

Rank the following compounds in order of decreasing acid strength (strongest at the top to weakest at the bottom of the list). Instructions

H2SO4 H2SO3 H2SeO3

Which of the following compounds are strong acids? Select all that apply.

H2SO4 HClO4 HI

The pH of a solution is a measure of its _____ concentration.

H3O+ ion

With reference to the table of Ka values provided, select all the equilibrium acid-base reactions that will favor the products.

HClO2 + HCOO- ⇌ HCOOH + ClO2- HF + OCl- ⇌ F- + HOCl

Select ALL the weak acids from the following list.

HF CH3CH2COOH HCN

Which of the following monoprotic acids would give a solution with the lowest pH at the same molarity?

HSO4- (pKa = 1.99) Reason: HSO4- has the lowest pKa value and is therefore the strongest acid with the lowest pH for solutions of the same concentration.

Select the two types of strong acids. Select all that apply.

Hydrohalic acids: HCl, HBr, and HI Oxoacids where the number of O atoms exceeds the number of ionizable H atoms by 2 or more: HNO3, H2SO4, and HClO4

Select all the expressions that correctly express the relationship between Ka and Kb for a conjugate acid-base pair.

Ka = Kw/Kb Ka x Kb = Kw

In order to determine whether a solution of NH4C2H3O2 is acidic, basic, or neutral, what two values could be compared?

Ka of NH4+ Kb of CH3COO-

Which of the following expressions correctly represents Kb for a weak base of general formula B?

Kb = [BH+][OH−]/[B]

Large Ka value Small Ka value

Low pKa value High pKa value

Which of the following statements correctly explains why it is reasonable to assume that for a weak acid [HA] at equilibrium is approximately equal to [HA]init under most circumstances?

Most molecules of the weak acid remain undissociated at equilibrium.

Which of the following common household substances are bases? Select all that apply.

NH3 Baking soda Lye

Which one of the following 0.1 M salt solutions will be basic?

NaCN

Which of the following are products of the reaction between the strong acid HCl and the strong base NaOH? Select all that apply.

NaCl Water (H2O)

Rank the following 0.1 M salt solutions in order of increasing pH (lowest pH at the top of the list). Instructions

NaHSO4 NH4NO3 NaHCO3 Na2CO3

Which of the following compounds can be classified as bases according to the Arrhenius definition? Select all that apply.

NaOH Ba(OH)2

Because Ka for a weak acid HA is ______, we can assume [HA]equilibrium ≈ [HA]initial.

small

Consider two solutions of the weak acid HCN, one with concentration 0.10 M and one with concentration 0.010 M. Select the statements that correctly describe these solutions.

The 0.10 M solution will have a higher [H3O+]. The 0.010 M solution will have a higher percent dissociation.

Which of the following are valid assumptions used in solving weak-acid equilibria problems? Select all that apply.

The [H3O+] from water is negligible. [HA] at equilibrium is approximately equal to [HA]init.

Select the correct statements describing a solution containing a salt composed of the cation of a strong base and the anion of a polyprotic acid. Select all that apply.

The anion will hydrolyze to produce either H3O+ or OH- ions depending on the relative values of Ka and Kb of the anion. The cation has no impact on the pH of the solution.

Which of the following factors will affect the relative strength of oxoacids? Select all that apply.

The electronegativity of the central nonmetal atom The number of O atoms attached to the central nonmetal atom

Which of the following statements accurately describe Bronsted-Lowry acid-base reactions? Select all that apply.

The reactants and products contain an acid and a base. Some species can act as either an acid or a base depending on the other species present.

Which of the following statements correctly describe a 1.0 M solution of KCN? Select all that apply.

The solution contains a significant concentration of the weak base CN-. The solution is basic.

Calculate [OH-] in a solution that has [H3O+] = 6.7 x 10-2 M. Is the solution acidic or basic?

The solution is acidic. 1.5 x 10-13 M Reason: [OH-] = Kw[H3O+]Kw[H3O+] = 1.0×10−146.7×10−2

Calculate [H3O+] in a solution with a [OH-] = 3.0 × 10-4 M. Is the solution acidic or basic?

The solution is basic. 3.3 × 10-11 M Reason: [H3O+] = Kw[OH−]Kw[OH-] = 1.0×10−143.0×10−4

Which of the following options correctly describe a solution with a pH = 8.00? Select all that apply.

The solution is basic. [OH-] > [H3O+]

Select all the factors that affect the ease with which a proton is released from a nonmetal hydride (represented by the general formula E-H.)

The strength of the E-H bond The electronegativity of the central atom (E)

Select the correct descriptions of the leveling (limiting) effect of water on strong acids and strong bases. Select all that apply.

The strongest acid in an aqueous solution is the hydronium ion. A strong acid will cease to exist in aqueous solutions because water will readily accept its proton to form hydronium ions.

True or false: A metal cation may behave as a Lewis acid in water to form a hydrated cation adduct.

True

Which of the following statements correctly describes a characteristics of polyprotic acids?

Usually only the first dissociation is taken into account in calculations involving polyprotic acids.

Which of the following common household substances are acids? Select all that apply.

Vitamin C Lemon juice Vinegar

Acidic solution Basic solution Neutral solution

[H3O+] > [OH-] [OH-] > [H3O+] [H3O+] = [OH-]

Arrange the following acids in order of greatest (at the top of the list) to least (at the bottom of the list) amount of H3O+ produced in solution. All the acids have the same initial concentration of HA. Instructions

^-2 ^-4 ^-8 ^-10

Lewis acid Lewis base Bronsted-Lowry acid Bronsted-Lowry base Arrhenius acid Arrhenius base

accepts an electron pair. donates an electron pair. donates an H+. accepts an H+. forms H3O+ ions in aqueous solution forms OH- ions in aqueous solution

A salt consisting of the anion of a weak _____ and the cation of a strong _____ yields a basic solution.

acid; base

Determine whether an aqueous solution of NH4ClO is acidic, basic, or neutral. Kb of NH3 = 1.8 × 10-5 Ka of HClO = 3.0 × 10-8

basic

The two types of strong acids are binary acids containing hydrogen bonded to a(n) _____ atom and oxoacids in which the number of O atoms exceeds the number of ionizable protons by _____ or more.

halogen; 2

Bases _______. Select all that apply.

have a bitter taste have a slippery feel in solution turn certain organic compounds specific colors

Acidic solutions have a _____ pOH than basic solutions.

higher

The stronger the acid, the _____ the [H3O+] at equilibrium and the _____ the value of Ka.

higher; larger

An acid contains one or more A base contains the unit H3O+ ions are produced OH- ions are produced

hydrogen atoms in its formula. OH in its formula. by an acid in aqueous solution. by a base in aqueous solution.

As the initial concentration of a weak acid decreases, the percent dissociation of the acid _____.

increases Reason: An increase in volume shifts the equilibrium position to favor more moles of ions.

Since pK = -logK, a low pK value corresponds to a _____ K value. A strong acid will have a _____ Ka value and a _____ pKa value.

large; large; low

For solutions with the same initial concentration of acid HA, the smaller the value of Ka, the _____ the % dissociation and thus the _____ the acid.

lower; weaker

The pH of a solution is a logarithmic value. This means that ______.

only digits after the decimal point are significant

In an organic acid such as CH3CH2COOH, the ionizable H atoms is/are ______.

only the H of the COOH group

Calculate the pH and [OH-] of a solution of a 1.5 M solution of HCl.

pH = -0.18 [OH-] = 6.7 x 10^-15 M Reason: pH = -log (1.5) = -0.18. Although the pH values of many familiar solutions fall between 0 and 14, in reality pH values can fall outside this range. Reason: [OH-] = Kw[H3O+]Kw[H3O+] = 1.0×10−141.5

Which of the following mathematical relationships are correct for an aqueous solution at 25oC? Select all that apply.

pH = -log[H3O+] pOH + pH = 14.00

Calculate the pH and [H3O+] of a 0.080 M solution of NaOH.

pH = 12.90 [H3O+] = 1.3 x 10^-13 M

Place the following pH values in order of increasing [H3O+]. Start with the pH that corresponds to the lowest [H3O+] at the top of the list. Instructions

pH = 8.5 pH = 7.2 pH = 4.3

Basic solution Neutral solution Acidic solution

pH > 7.00 pH = 7.00 pH < 7.00

Acids _______. Select all that apply.

participate readily in proton-transfer reactions react with active metals to release H2 (g) have a sour taste

In a Bronsted-Lowry acid-base reaction, equilibrium will favor the _____ if the reacting acid and base are strong. The reaction will always favor the formation of the _____ acid and base.

products; weaker

Acid dissociation is represented by the general equation HA + H2O (l) ⇌ H3O+ (aq) + A- (aq). For a strong acid the equilibrium lies far to the _____ and [H3O+] is much _____ than [HA]. For a weak acid, on the other hand, the equilibrium lies far to the _____ and [H3O+] is much _____ than [HA].

right; higher; left; lower

The direction of an acid-base equilibrium depends on the relative strengths of the acids and bases involved. Since strong acids and strong bases readily accept and donate protons, the equilibrium will always favor the reaction of the _____ acid and base and the formation of the _____ acid and base.

stronger; weaker

In terms of the Arrhenius definition of acids and bases, neutralization is described as _______.

the complete reaction of all H+ ions from the acid with all the OH- ions from the base

The anion, A-, of a weak acid is a(n) ______ because anions react with solvent water to produce HA and OH-.

weak base

HCN has a Ka value of 6.3 x 10-10 while acetic acid has a Ka value of 1.8 x 10-5. HCN is a _____ acid than acetic acid and will therefore have a _____ pKa value.

weaker; higher

Given the acid-base equilibrium HCN (aq) + HCO3- (aq) ⇌ CN- (aq) + H2CO3 (aq); pKa for HCN = 9.2 and pKa for H2CO3 = 6.3. HCN is a _____ acid than H2CO3, and the equilibrium as written will lie to the _____ and favor the formation of the _____.

weaker; left; reactants Reason: A higher pKa value (which corresponds to a smaller Ka value) indicates a weaker acid. HCN is therefore weaker than H2CO3, and the reaction will favor the reactants.

In general the stronger an acid is, the _____ its conjugate base will be. Thus the conjugate base Cl- is _____ because its conjugate acid HCl is strong.

weaker; weak