CHEM 1040 Ch. 17

Which is the correct equation for the calculation of percent ionization of the weak acid HA in aqueous solution?

% ionization = [H+]eq/[HA]0 × 100%

Which of the following statements correctly describe carboxylic acids, represented by the general formula RCOOH? Select all that apply.

-As R changes, the strength of the acid changes. -Carboxylic acids are weaker acids than hydrohalic acids such as HCl. -Carboxylic acids are organic acids represented by the general formula RCOOH.

Which of the following statements correctly describe the relative strengths of acids and bases, and of conjugate acid-base pairs? Select all that apply.

-CH3COO- is a relatively stronger base than Cl3CCOO-. -Iodide ion, the conjugate base of HI, is a weak base.

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

-For very weak acids (Ka < 10-4) at concentrations greater than 0.10 M, [HA]eqm ≈ [HA]0, the original acid concentration. -The [H3O+] from water is negligible.

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.

An aqueous NaCl solution was found to have a pH = 7.00. Select all the statements that correctly describe this solution.

-Neither Na+ nor Cl- reacts with water. -The NaCl solution was neutral.

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

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

Which statements are correct when calculating Kb of a 0.040 M NH3 solution with a pH = 10.93 at 25°C? Select all that apply.

-[OH-] may be calculated from pOH -[NH4+]eq = [OH-]eq and [NH3]eq = [NH3]initial - [OH-]eq

The [OH-] of a 0.010 M Ba(OH)2 solution is _____ M and the pOH is equal to _____.

0.020, 1.70

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

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

base, stronger

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

donor; hydrogen

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

false

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

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

higher; larger

The autoionization of water is a process where water ionizes very slightly to form ____ ions and ____ ions. (Remember to include charges for the ions but no symbols to indicate super- or sub-scripts.)

hydronium, hydroxide

Which of the following mathematical relationships are correct for an aqueous solution at 25°C? 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 × 100%. This is called the ___ ionization and is a measure of acid strength.

percent

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

The aqueous solutions of a strong acid and a weak acid are compared. Match each acid with the species that is/are present in the greatest concentration in the final solution. Note that the generic formula HA is used for each acid and A- for the conjugate base in both cases.

strong acid --> H3O+, A- weak acid-->HA

A(n) ___ acid is one that ionizes only slightly in water, whereas a(n) ___ acid ionizes completely.

weak strong

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 compounds are strong acids? Select all that apply.

HI HClO4 H2SO4

Correctly order the steps necessary to solve weak-acid equilibrium problems, starting with the first step at the top of the list.

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

A 0.15 M solution of butanoic acid, CH3CH2CH2COOH (or C3H7COOH), contains 1.51 × 10-3 M H3O+. What is the Ka of butanoic acid?

1.5 × 10-5

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

11.45

H3PO4--> H2CO3---> CH3COOH-->

3 2 1

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 following statements correctly explains why even distilled and deionized H2O contains some ions?

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

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

H20 HF HBr

Which of the following statements correctly describes the relative strength of binary acids?

H2S is a stronger acid than H2O.

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

Ka = KwKbKwKb Ka × Kb = Kw

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

Kb = [HB+][OH−]/[B]

If the pH of a 0.010 M solution of a strong base is 12.30, what is the identity of the base?

The base could be Ba(OH)2.

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

acceptor, lone, electrons, covalent

The strength of an acid is measured by its tendency to ___ and produce ____ ions in aqueous solution.

ionize, hydrogen