Chem 112 Chapter 18

Characteristics of Polyprotic acids

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

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 - The solution will be basic - CN- will behave as a base when it reacts with water

Select all the weak acids from the following list: HBr HCN HF HNO3 CH3CH2COOH

- HCN - HF - CH3CH2COOH

Describe the constant Ka

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

Correctly express the relationship between Ka and Kb for a conjugate acid-base pair

- Ka x Kb = Kw - Ka= (Kw/Kb)

HCN is a weak acid with Ka = 6.2 x 10^-10. Which of the following options correctly reflect the steps required to calculate the pH of a solution containing 0.150 M KCN

- Kb of CN- = 1.6 x 10^-5 - pH 11.18

Which of the following anions will produce a neutral solution in water?

- NO3- - Cl- - I-

Which of the following statements accurately describe Bronsted-Lowry acid-base reactions?

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

Consider two solutions of weak acid HCN, one with concentration 0.10M and one with concentration .010M, what is true about this?

- The 0.10M will have a higher [H3O+] - The .010M solution will have higher percent dissociation

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

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

Which of the following common household substances are bases?

-baking soda -NH3 -lye

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

0.00010 M

The anion of a weak acid can interact with H2O according to the balanced equilibrium equation A-(aq) + H2O(aq) <=> HA(aq) + OH-(aq).

1. A- is a weaker base than OH- and the equilibrium will lie to the left 2. The [HA] in solution will be relatively low 3. The pH of this solution will be greater than 7

Match the relative concentrations of hydronium and hydroxide with the type of solutions: 1. Acidic solution 2. Basic solution 3. Neutral solutions

1. Acidic solution: [H3O+] > [OH-] 2. Basic solution: [OH-]> [H3O+] 3. Neutral solutions: [H3O+] = [OH-]

Arrhenius Acid-Base Definition: 1. An acid contains one or more 2. A base contains the unit 3. H3O+ ions are produced 4. OH- ions are produced

1. An acid contains one or more: hydrogen atoms in its formula 2. A base contains the unit: OH in its formula 3. H3O+ ions are produced: by an acid in aqueous solution 4. OH- ions are produced: by a base in aqueous solution

Compounds that are strong bases

1. Cao 2. NaOH

What are the products of the reaction between the strong acid HCl and the strong base NaOH? H2O H3O+ OH- NaCl

1. H2O 2. NaCl

Match each acid correctly to the number of ionizable protons: 1. H3PO4 2. H2CO3 3. CH3COOH

1. H3PO4: 3 2. H2CO3: 2 3. CH3COOH: 1

Arrange the following acids in order of greatest to least amount of H3O+ produced in solution

1. HClO2 (Ka = 1.1 x 10^-2) 2. HF (Ka = 6.8 x 10^-4) 3. HClO (Ka = 2.9 x 10^-8) 4. HCN (Ka = 6.2 x 10^-10)

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

1. HClO2 + HCOO- <=> HCOOH + ClO2- 2. HF + OCl- <=> F- + HOCl

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

1. KA OF NH4+ 2. KB OF CH3COO-

Rank the follwoign 0.1M salt solutions in order of increasing pH (lowest to highest)

1. NaHSO4 2. NH3NO3 3. NaHCO3 4. Na2CO3

Which of the following statements correctly describes a 1.0 M of KCN?

1. The solution contains a significant concentration of the weak base CN- 2. The solution is basic

Correctly order the steps necessary to solve weak-acid equilibria problems

1. Write the balanced equation and Ka expression 2. Define x as the unknown change in concentration that occurs in the reaction and assume x is small compared to [HA] initial. 3. Construct a reaction table that incorporates x, and solve for x by substituting values into the Ka expression. 4. Check that assumptions are justified, using 5% test. If not justified, use the quadratic formula to find x.

Which of the following correctly describe a solution with a pH of 8.00?

1. [OH-] > [H3O+] 2. The solution is basic

The following relationship is true for an aqueous solution at 25°C

1. pOH + pH = 14.00 2. pH = -log[H3O+]

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

11.45 ([OH-]^2)/0.25 = 3.2 x 10^-5. [OH-] = (1/2 (0.25 x (3.2 x10^-5))) = 2.8 x 10^-3 and [H3O+] = (1 x10^-14)/(2.8 x 10^-3) = 3.57 x 10^-12 pH = -log(3.57 x 10^-12) =11.45

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

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 [H3O+] = [NO2] = 2square root (Ka x [HNO2]

Calculate the Ka value for the anilium ion (C6H5NH3+) if Kb for aniline (C5H5NH2) is 4.0 x 10^-10

2.5 x 10^-5 Ka = (1 x 10^-14)/Kb = (1 x 10^-14)/(4 x 10^-10) = 2.5 x 10^-5

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. pH = 7.2 pH = 4.3 pH = 8.5

8.5 7.2 4.3

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 the H+.

Acceptor, Lone, Electrons, Covalent

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

Acidic

An acid donates a proton to form its conjugate _____ which therefor has one less ______ atom and one more ______ charge than its acid

Base, Hydrogen, Negative

Classify acids and bases according to their physical and chemical behavior

Bases: Bitter Taste & Soapy Feel Acids: React with active metals to produce H2 & Sour Taste

1. Basic Solution 2. Neutral Solution 3. Acidic Solution

Basic Solution: pH > 7.00 Neutral Solution: pH = 7.00 Acidic Solution: pH < 7.00

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 _____ ion, which has the formula H3O+.

Electron, Proton, Hydronium

Which of the following statements correctly describes why even distilled and deionized H2O contains some ions?

H+ can be transferred from one H2O molecule to another, forming H3O+ and OH- ions

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

H2PO4-/PO4^3-

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

H3O+ ion

Which are strong acids? HBr H2SO4 HF CH3COOH HNO3

HBr H2SO4 HNO3

Which of the following species could be either an acid or a base? HCO3- H2O H2PO4- NH4+ SO4^2-

HCO3- H2O H2PO4-

All strong acids and bases appear equally as strong in H2O. This is because in water the strongest acid 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.

Hydronium, Hydroxide, Leveling

In order to determine the overall acidity of a 0.1 M solution of NaHCO3, the ___ and ___ values for HCO3- must be compared

Ka; Kb

Large Ka value Small Ka value

Large Ka value: low pKa value Small Ka 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

The two general types of weak base include molecules that contain one or more __ atoms, and the anions of weak ______.

N; acids

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

NaCN CN- is the conjugate base of a weak acid; Na+ will not react

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______.

Neutralization

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

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

Raise 10 to the power of the negative pH value.

Acid ionization 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, the equilibrium lies far to the ______ and [H₃O⁺] is much _____ than [HA].

Right; Higher; Left; Lower

The aqueous solution of a strong acid and weak acid are compared. match each acid with the species that is/are present in the greatest concentration in the final solution.

Strong Acid: H3O+, A- Weak Acid: HA

An Acid-Base Reaction occurs when one species loses a proton and another species simultaneously gains a proton. It therefore can be viewed as a proton-____ process.

Transfer

Given the acid-base equilibrium HCN (aq) + HCO- (aq) ---> CN- (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

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

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

[OH-] = Kw/[H3O+] = (1.0 x 10^-14)/(6.7 x 10^-2) -1.5 x 10^-13 M -The solution is acidic [H3O+] > [OH-], so the solution is acidic

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

base; stronger

in a bronsted-lowry acid-base reaction, the acid reacts to form its ______ ____ and the base will form its _____ ____

conjugate base; conjugate acid

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

halogen; 2

Acidic solution have a ___ pOH than basic solutions

higher

A monoprotic acid has _____ ionizable protons, whereas a diprotic acid has _____ ionizable protons

one; two

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

only the H of the COOH group

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

pH

A salt consisting of the anion of a ____ acid and the cation of a ____ base yields a basic solution

strong; weak

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

stronger

HCN has a Ka value of 6.3*10^-10 while acetic acid has a Ka value of 1.8*10^-5. HCN is a ___ acid than acetic acid and will therefore have a ____ pKa value

weaker; higher