Chem 2 Chapter 16
A Bronsted-Lowry acid is a proton _____ and must therefore contain at least one ionizable _____ atom in its formula.
donor; hydrogen
Which is the correct equation for the calculation of percent ionization of the weak acid HA in aqueous solution?
% ionization = [H+]eq / [HA]0 x 100%
Which of the following statements correctly describes the relative strength of binary acids?
H2S is a stronger acid than H2O.
Select all the acids below that are diprotic and polyprotic.
H2SO4 H2C6H6O6
Which statement best explains the trend in acid strength: H2SO4 > H2SO3 > H2SeO3?
H2SO4 is stronger than H2SO3 because it has more O atoms.
Which of the following statements correctly explain the relative strengths of the oxoacids shown: HBrO < HClO < HClO2 < HClO3? Select all that apply.
HBrO is weaker than HClO because Br is less electronegative than Cl. HClO3 is stronger than HClO2 because HClO3 has more O atoms.
Which of the following species could act as EITHER an acid OR a base? Select all that apply.
HCO3- H2O H2PO4-
Which of the following compounds are strong acids? Select all that apply.
HI HClO4 H2SO4
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.
I- NO3- Cl-
Select all the statements that correctly describe the acid-base behavior of H2O.
In aqueous NH3, water acts as a Bronsted acid. In aqueous HCl, water acts as a Bronsted base. Water is amphoteric.
Which of the following options shows the correct mathematical operation required to calculate [H3O+] for a solution with a pH of 3.52?
[H3O+] = 10-3.52 = 3.0 x 10-4 M
Which of the following gives the correct mathematical operation required to calculate the [H3O+] given a pH of 5.0?
[H3O+] = 10^-5.0
A salt consisting of the _____ of a strong acid and the _____ of a strong base yields a neutral solution.
anion; cation
Order the steps for calculating the ka of a weak acid, given a solution of known concentration and pH
(1) Calculate the equilibrium [H3O+] (and thus [A-]) for the solution from the given pH. (2) Calculate the equilibrium concentration of the weak acid. (3) Substitute [H3O+], [A], and [HA] into the equilibrium constant expression. (4) Solve for Ka.
Order the following steps in determining the pH of a solution of a weak acid of known concentration.
(1) Construct an equilibrium table and enter the starting acid concentration (2) Use the balanced ionization equation to determine the changes in concentration of all species. (3) Express the equilibrium concentration of all species in terms of x, which is the [H3O+] at equilibrium. (4) Enter all equilibrium concentration into the equilibrium expression and solve for x. (5) Calculate pH based on the solution to the equilibrium expression equation.
Arrange the following compounds in order of increasing acid strength (weakest at the top to strongest at the bottom of the list).
(1) H2O (2) HF (3) HBr
Rank the sequence of the steps you would use to calculate Kb starting with the pH of a solution of a weak base of known initial concentration.
(1) Use pH to calculate pOH. (2) Calculate [OH-] from pOH. (3) Use [OH-] and reaction stoichiometry to calculate the equilibrium concentration of HB+ and B. (4) Use the equilibrium expression and calculate the value of Kb.
Match the relative concentrations of hydronium and hydroxide with the type of solution.
- Acidic solution: [H3O+]>[OH-] - Basic solution: [OH-]>[H3O+] - Neutral solution: [H3O+]=[OH-]
Place the steps required to calculate the pH of a 0.10 M NaNO2 solution in the correct order. Ka for HNO2 is 4.5 × 10-4.
- Kb for NO2- = 1.010^-14/4.510^-4 = 2.22*10^-11 - 2.22*10^-11 = [OH-][HNO2]/[NO2] = x^2/.10 - [OH] = square root of (2.22*10^-11)(.10) - pOH = -log(1.49*10^-6) = 5.82 - pH = 14.00 - 5.82 = 8.17
Which of the following solutions of HCN will have the greatest percent ionization?
0.00010 M Reason: The percent ionization of a weak acid increases as the initial concentration of the acid decreases.
Rank the following carboxylic acids in order of increasing acid strength (weakest at the top to strongest at the bottom of the list).
1. CH3COOH 2. BrCH2COOH 3. ClCH2COOH 4. Cl3CCOOH
Match each acid correctly to the number of ionizable protons. Instructions
1. H3PO4: 3 2. H2CO3: 2 3. CH3COOH: 1
Rank the following 0.1 M salt solutions in order of increasing pH (lowest pH at the top of the list).
1. NaHSO₄ 2. NH₄NO₃ 3. NaHCO₃ 4. Na₂CO₃
A 0.10 M CH3COOH solution has a [H3O+] = 1.3 x 10-3 M. What is the percent ionization of CH3COOH with a Ka = 1.8 x 10-5?
1.3% Reason: % ionization =[H3O+]eq/[CH3COOH]0 x 100 = 1.3x10−3/0.10 x 100 = 1.3%
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 0.25 M solution of ethanolamine (Kb = 3.2 x 10-5)?
11.45 Reason: [OH-]2/0.25 = 3.2 x 10-5. [OH-] = √0.25x3.2x10-50.25x3.2x10-5 = 2.8 x 10-3 and [H3O+] = 1.0x10-14/2.8x10-3 = 3.57 x 10-12 pH = -log(3.57 x 10-12) = 11.45
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 Reason: [H3O+] = [NO2-] = 2⎯⎯√Kax[HNO2]
Benzoic acid, C6H5CO2H, has a Ka of 6.5 x 10-5. What is the pH of a 0.40 M solution of benzoic acid?
2.29 Reason: [H3O+] = [C6H5CO2-] = 2⎯⎯√Kax[C6H5CO2H] = 5.1 x 10-3; pH = -log(5.1 x 10-3) = 2.29
Calculate the kaka value for the anilium ion (C6H5NH3+) if kb for aniline (C6H5NH2) is 4.0 × 10−10
2.5 × 10−5 Reason: ka = 1.0 × 10−14/kb = 1.0 × 10−14/4.0 × 10−10 = 2.5 × 10−5
Without using a calculator, select the pH below of a solution whose [H3O+] is 1.8 × 10−510-5 M.
4.74
When calculating the pH of a weak acid solution it is justified to assume that [H3O+] derived from the acid is negligible when the [H3O+] is less than ______ % of the initial acid concentration.
5
When solving for the [H3O+] or pH of a weak acid, the quadratic equation must be used if the acid's ionization is greater than ______ %.
5
A 0.10 M solution of HCN (Ka = 4.9 x 10-10) is 7.0 x 10-3 % ionized. What is the pH of this solution?
5.15 Reason: [H3O+] = 2⎯⎯√4.9x10-10x0.10 = 7.0 x 10-6 pH = -log(7.0 x 10-6) = 5.15
Calculate the kb value for the acetate ion (CH3COO-) if the ka value for acetic acid (CH3COOH) is 1.8 × 10-5.
5.6 × 10−10 Reason: kb = 1.0 × 10−14/ka = 1.0 × 10−14/1.8 × 10−5= 5.6 × 10−10
Without using a calculator, select the pH below of a solution whose [H3O+] is 2.7 × 10−810-8 M.
7.57
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.
8.5 7.2 4.3
Which of the following statements correctly describe amphoteric hydroxides? Select all that apply.
Amphoteric hydroxides react with both acids and bases. Al(OH)3 is an amphoteric hydroxide.
You are given a weak acid solution of known concentration and known pH. Which of the following would not be part of the process of determining the kaka of the acid?
Assume that the equilibrium [HA] is equal to the initial [HA]. Convert [H3O+]to [OH-] for the salt solution.
Which of the following species are Lewis acids? Select all that apply.
BF3 Cu2+
Match the following pH values with the type of aqueous solution at 25oC.
Basic = pH>7.00 Neutral = pH=7.00 Acidic = pH<7.00
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.
Both NH4+ and CN- will hydrolyze (react with water) in aqueous solution. CN- will behave as a base when it reacts with water. The solution will be basic.
Which of the following statements correctly describe salt hydrolysis?
Both the anion and the cation of a water-soluble salt may interact with water. Salt hydrolysis causes the pH of the resulting solution to be above or below 7.00. The ions produced by dissociation of a salt in water react with H2O.
Which of the following nonmetal oxides produce a weak acid when dissolved in water? Select all that apply.
CO2 P4O10
Which of the following statements correctly describe carboxylic acids, represented by the general formula RCOOH? Select all that apply.
Carboxylic acids are weaker acids than hydrohalic acids such as HCl. Carboxylic acids are organic acids represented by the general formula RCOOH. As R changes, the strength of the acid changes.
Which of the following oxides will NOT produce a basic solution in water?
Cl2O Reason: Group 7A oxides (nonmetallic oxides) form acidic solutions in water. Cl2O + H2O → 2HClO (hypochlorous acid)
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: in carboxylic acids, the ionizable proton is the one bonded to oxygen. H atoms bonded to C do not ionize
Which of the following formulas can be used to represent the proton in aqueous solution? Select all that apply.
H+ H3O+
The hydrogen phosphate ion, HPO42-, can act as both a Bronsted acid and Bronsted base in water. Select all the options that correctly describe the reaction that occurs when HPO42- acts as a Bronsted base in water.
H2O acts as the Bronsted acid. OH- is one of the products. H2PO4- is one of the products.
Which statement correctly explains why even distilled and deionized H2O contains some ions?
H2O can autoionize, producing a small concentration of H3O+ and OH- ions.
Which of the following are not steps in a process to determine the pH of a solution of a weak acid whose concentration is known? Select all that apply.
Include the concentration of water in the equilibrium expression. Assume that the acid is fully ionized in aqueous solution.
Determine if aqueous solutions of the following salts are acidic, basic, or neutral.
KBr : neutral NH4INH4I : acidic KCN : basic
Which of the following salt solutions will be basic, assuming that all have concentrations of 0.1 M? Select all that apply.
KCH3COO NaCN
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-
Select all the expressions that correctly express the relationship between Ka and Kb for a conjugate acid-base pair.
Ka*Kb=Kw Ka=Kw/Kb
Which of the following correctly represents Kb for a weak base of general formula B?
Kb = [HB⁺] [OH⁻] / B
Select the species from the list below that are not strong acids. Select all that apply.
NH4+ HF HNO2
Select all the options that correctly account for the behavior of NH4Cl in aqueous solution.
NH4+ + H2O ⇌ NH3 + H3O+ The solution will have a pH < 7.00.
What is the conjugate base of HNO2 if it reacts as a Bronsted acid in H2O?
NO2-
Which of the following types of substances are classified as acids only under the Lewis definition? Select all that apply.
Small, highly charged metal cations Molecules with electron deficient central atoms
The pH of a salt solution containing a small, highly charged metal cation is influenced by the hydrolysis reaction of the metal ion. Which of the following statements correctly explain the hydrolysis reaction of these metal cations? Select all that apply.
Small, highly charged metal cations accept electron pairs from water molecules and form hydrated ions. A hydrated metal ion produces an acidic solution because the metal ion withdraws electron density from the O-H bond, facilitating loss of H+.
Select all the statements that correctly describe the acid-base behavior of oxides.
Some metals from Group 3A form amphoteric oxides. Alkali metal oxides are basic. Most nonmetal oxides are acidic.
Which of the following options correctly describe strong acids and bases in aqueous solution? Select all that apply.
Strong bases dissociate completely in aqueous solution. For a strong acid in water, [H3O+] is equal to the acid concentration.
An aqueous NaCl solution was found to have a pH = 7.00. Select all the statements that correctly describe this solution.
The NaCl solution was neutral. Neither Na+ nor Cl- reacts with water.
How does a conjugate acid compare to its conjugate base? Select all that apply.
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 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
Calculate and compare the pH values for 0.10 M solutions of NH4Br (Ka 5.6 × 10-10) and Al(NO3)3 (Ka 1.3 × 10-5). Which of the following statements correctly describe the acidity of these solutions? Select all that apply.
The pH of the Al(NO3)3 solution is 2.94. The NH4Br solution has a higher pH than the Al(NO3)3 solution.
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 the relationship between a weak acid or base and its conjugate base or acid? Select all that apply.
The stronger a base is, the more strongly the formation of its conjugate acid is favored. The weaker an acid is, the stronger its conjugate base will be.
True or false: A strong conjugate acid is not the same thing as a strong acid.
True
True or false: pH is a measure of hydronium ion concentration.
True
Which of the following statements are correct about conjugate acids and bases?
Water is a weak conjugate acid. Iodide is a weak conjugate base. Acetate is a strong conjugate base.
Under what conditions does it become necessary to use the quadratic equation to solve for [H3O+] or pH?
When calculating [H3O+] for a weak acid solution whose ionization is more than 5%
When calculating the pH of a weak acid or weak base solution, we assume that the [H3O+] or [OH-] due to ionization is negligible. When is this assumption justified?
When the acid/base shows less than 5% ionization
Select all the statements that correctly describe the constant Ka.
[H2O] is not included in the Ka expression for a given acid. Ka is the acid ionization constant.
Calculate the pH and [H3O+] of a 0.080 M solution of NaOH.
[H3O+] = 1.3 x 10-13 M pH = 12.90
Which of the following options correctly represent the relationship between [H3O+] and [OH-] in aqueous solutions at 25oC? Select all that apply.
[H3O+][OH-]= 1.0 E -14 [H3O+]= 1.0 E -14/ [OH-]
Calculate the pH and [OH-] of a solution of a 1.5 M solution of HCl.
[OH-] = 6.7 x 10-15 M pH = -0.18
Which of the following options correctly describe a solution with a pH = 8.00? Select all that apply.
[OH-] > [H3O+] The solution is basic.
A 0.10 M NH4Cl solution is found to be acidic. Select the statement that correctly represents the relative [H3O+] and [OH-] in this solution.
[OH-]< [H3O+], the solution is basic.
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 at a given concentration.
^-2 ^-4 ^-8 ^-10
A Bronsted-Lowry base is a proton _____
acceptor
A Lewis acid is any species that _____ an electron pair, whereas a Lewis base is a species that _____ an electron pair.
accepts; donates
A salt consisting of a small, highly charged metal cation and the anion of a strong acid yields a(n) _____ solution.
acidic
A salt in which the cation is the conjugate acid of a weak base will produce an ______ solution. (Assume that the anion does not hydrolyze.)
acidic
Determine whether an aqueous solution of NH4NO2NH4NO2 is acidic, basic, or neutral. κb of NH3 = 1.8 × 10−5 κb of HNO2 = 4.5 × 10−4
acidic Reason: κb < κa, so pH < 7
In general, nonmetal oxides tend to be _____ while metal oxides tend to be _____.
acidic, basic
A compound that can act as either a Bronsted acid or a Bronsted base is said to be ______.
amphoteric
A salt in which the anion is the conjugate _____ of a weak _____ will produce a basic solution. (Assume that the cation does not hydrolyze.)
base, acid
An amphoteric metal hydroxide behaves not only as a(n) _______ (as expected given its OH- anion), but also as a(n) _______.
base, acid
Water functions as a(n) _____ in reactions with stronger acids, and functions as a(n) ______ in reactions with stronger bases.
base, acid
An acid donates a proton to form its conjugate ______, , which therefore has one less ______ atom and one more ______ charge than its acid.
base, hydrogen, negative
The strength of a weak base is indicated by its _______ -ionization constant Kb. The greater the value of Kb, the ______ the base.
base, stronger
If a salt contains a cation and an anion that both hydrolyze, the acidity or basicity of the solution is predicted by comparing the K<sub>a</sub> value of the salt's ______ _ (which acts as a weak acid) to the K<sub>b</sub> value of the salt's _______ _ (which acts as a weak base).
cation, anion
In a Bronsted-Lowry acid-base reaction, the acid reacts to form its _____ ______ and the base will form its _____ _______.
conjugate base, conjugate acid
A strong ______ acid is not necessarily the same thing as a strong acid. Bicarbonate (HCO3-) is a weak base, and therefore H2CO3 is considered a strong ______ ; but H2CO3 does not ______ completely in water.
conjugate, conjugate, ionize
In an aqueous solution at a given temperature, the product [H3O+][OH-] has a _____ value. This product is equal to _____ at 25oC.
constant, 1.0 x 10-14
The stronger the acid, the _____ the [H3O+] at equilibrium and the _____ the value of Ka.
higher; larger
When an ionic compound dissociates in water, the separated ions may react with H2O to produce H3O+ or OH- ions. This process, known as salt ______, may affect the _______ of the salt solution.
hydrolysis, pH
An acid can be defined as a substance that loses one or more H+ ions when dissolved in water. In aqueous solution, the H+ ion combines with H2O to produce the ______ ion, which has the formula H3O+.
hydronium
The autoionization of water is a process whereby water ionizes to a small extent to form ______ ions and _______ ions.
hydronium, hydroxide
Oxoacids have the general formula HnXOm, where X represents a central atom. For the same element X, acid strength will ______ as the number of O atoms increases. For the same number of O atoms, acid strength increases as the ______ of element X increases.
increase, electronegativity
As the initial concentration of a weak acid decreases, the percent ionization of the acid ______.
increases
Strong acids and bases are assumed to ______ completely in aqueous solution, making them strong electrolytes.
ionize
The strength of an acid is measured by its tendency to _____ and form ions in solution.
ionize, hydronium
For solutions with the same initial concentration of acid HA, the smaller the value of Ka, the ______ the % ionization and thus the ______ the acid.
lower, weaker
The higher the pH value, the _____ the [H3O+] and the _____ acidic the solution will be.
lower; less
In organic acids, the ionizable hydrogen is bound to a(n) _____ atom.
oxygen
Which of the following mathematical relationships are correct for an aqueous solution at 25oC? Select all that apply.
pOH + pH = 14.00 pH = -log[H3O+]
The degree of ionization for a weak monoprotic acid HA is given by the expression [H+]eq/[HA]0 x 100. This is called the _____ ionization and is a measure of acid strength.
percent
A Bronsted acid-base reaction occurs when one species loses a(n) ______ and another species simultaneously ______ a proton.
proton, gains
The two factors that influence the extent of ionization of an acid are the _____ and ______ of the HX bond, where HX is the general formula of an acid.
strength, polarity
In the reaction illustrated here, a proton is transferred from ______, , which is the Bronsted _______, to ______, which acts as the Bronsted ______.
water (h20), acid, NH3, base
A strong acid ionizes completely in water; therefore it has a ______ conjugate base. A weak base reacts only partially with water; therefore it has a ______ conjugate acid.
weak; strong
In general, the stronger an acid is, the _____ its conjugate base will be. The stronger the acid, the more the equilibrium shown below will favor the formation of the _____. HA + H2O ⇌ H3O+ + A-
weaker, conjugate base
