CHEM113 - SB 17.9-10

Which of the following acids are polyprotic? Multiple select question. H3PO4 ClCH2COOH H2SO3 CH4

H3PO4 H2SO3

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

H3PO4 --------> 3 H2CO3 --------> 2 CH3COOH ------> 1

Select all the options that correctly account for the behavior of NH4Cl in aqueous solution. Multiple select question. NH4+ + H2O ⇌ NH3 + H3O+ The solution will have a pH < 7.00. H2O + H2O ⇌ H3O+ + OH- The solution will be basic. Cl- + H2O ⇌ HCl + OH-

1. NH4+ + H2O ⇌ NH3 + H3O+ Reason: NH4+ is a weak acid. It reacts with H2O to produce H3O+ ions. The resulting solution is acidic. 2. The solution will have a pH < 7.00. Reason: NH4+ is a weak acid. It reacts with H2O to produce H3O+ ions. The resulting solution is acidic, with a pH < 7.00.

Which of the following statements accurately describe the characteristics of polyprotic acids? Select all that apply. Multiple select question. Polyprotic acids are generally weak acids. In general Ka3 > Ka2 > Ka1. In calculations involving polyprotic acids we generally only take into account H3O+ formed from the first ionization. A polyprotic acid has more than one ionizable proton. Polyprotic acids usually lose all ionizable protons in a single step.

1. Polyprotic acids are generally weak acids. 2. In calculations involving polyprotic acids we generally only take into account H3O+ formed from the first ionization. 3. A polyprotic acid has more than one ionizable proton.

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

CN- will behave as a base when it reacts with water. Reason: CN- will accept a proton from H2O; hence, it acts as a base. The solution will be basic. Reason: Since CN- is a stronger base than NH4+ is an acid, the solution will be basic. Both NH4+ and CN- will hydrolyze (react with water) in aqueous solution. Reason: NH4+ is the conjugate acid of the weak base NH3, and CN- is the conjugate base of the weak acid HCN. Both these ions will react with H2O via acid-base reactions.

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. Multiple select question. F− Cl− NO3- I−

Cl− NO3- I−

Determine if aqueous solutions of the following salts are acidic, basic, or neutral. KBr NH4I KCN acid basic neutral

KBr -------> neutral NH4I ------> acidic KCN -------> basic

Match the correct qualitative prediction for a salt solution in which both its cation and anion hydrolyze. Ka (of the salt's cation) > Kb (of the salt's anion) Ka (of the salt's cation) < Kb (of the salt's anion Ka (of the salt's cation) ≈ Kb (of the salt's anion)

Ka (of the salt's cation) > Kb (of the salt's anion) -----> The salt solution is acidic Ka (of the salt's cation) < Kb (of the salt's anion -----> the salt solution is basic Ka (of the salt's cation) ≈ Kb (of the salt's anion) ----> the salt solution is neutral

Which of the following statements correctly describe the acid-base properties of a 1.0-M solution of methylammonium fluoride (CH3NH3F)? Select all that apply. Ka of HF = 7.1 × 10-4 and Kb of CH3NH2 = 4.4 × 10-4 Multiple select question. Ka of CH3NH3+ = 2.3 × 10-11 Kb of F- = 7.1 × 10-4 The solution will be slightly acidic because Ka of CH3NH3+ > Kb of F-. Both CH3NH3+ and F- will hydrolyze (react with water) in aqueous solution. F- will behave as an acid when it reacts with water.

Ka of CH3NH3+ = 2.3 × 10-11 Reason: Ka of CH3NH3+ = KwKb, CH3NH2KwKb, CH3NH2 = 1.0×10−144.4×10−41.0×10-144.4×10-4 = 2.3 × 10-11 The solution will be slightly acidic because Ka of CH3NH3+ > Kb of F-. Reason: The ionization constants indicate that CH3NH4+ is more able to produce [H3O+] in water than F- is able to hydrolyze to produce [OH-]. Both CH3NH3+ and F- will hydrolyze (react with water) in aqueous solution. Reason: Both these ions will react with H2O in acid-base reactions: CH3NH3+ + H2O ⇌ CH3NH2 + H3O+ and F- + H2O ⇌ HF + OH-

In order to determine whether a solution of NH4C2H3O2 is acidic, basic, or neutral, what two values could be compared? Multiple select question. Kb of CH3COO- Ka of NH4+ Kb of NH3 Ka of CH3COOH

Kb of CH3COO- Reason: The solution will contain CH3COO- ions, which act as a weak base. We must consider the Kb value for CH3COO-, not the Ka value for CH3COOH, although of course these values are related. Ka of NH4+ Reason: The solution consists of a weak acid (NH4+) and a weak base (CH3COO-); therefore the Ka value of NH4+ must be compared to the Kb value of CH3COO-.

Which of the following salt solutions will be basic, assuming that all have concentrations of 0.1 M? Select all that apply. Multiple select question. NaCN KCl NH4NO3 KCH3COO

NaCN Reason: CN- is the conjugate base of a weak acid; Na+ will not react with H2O. KCH3COO Reason: CH3COO- is the conjugate base of a weak acid and will produce a basic solution. K+ will not react with H2O and therefore does not affect the pH of the solution.

An aqueous NaCl solution was found to have a pH = 7.00. Select all the statements that correctly describe this solution. Multiple select question. Only Na+ reacts with water. Neither Na+ nor Cl- reacts with water. Only Cl- reacts with water. The NaCl solution was neutral.

Neither Na+ nor Cl- reacts with water. Reason: The pH is due to the autoionization of water. [H3O+] = [OH-] = 1.0 x 10-7 M; hence, pH = 7.00 (neutral). The NaCl solution was neutral. Reason: pH = 7.00 implies neutrality.

Which of the following statements is NOT a characteristic of polyprotic acids? Multiple choice question. A polyprotic acid has more than one ionizable proton. Polyprotic acids ionize in a stepwise fashion. Polyprotic acids are generally strong acids in their first ionization. In general Ka1 > Ka2 > Ka3.

Polyprotic acids are generally strong acids in their first ionization. Reason: Almost all polyprotic acids are weak acids. The only strong polyprotic acid is H2SO4.

Which of the following statements correctly describe salt hydrolysis? Multiple select question. Salt hydrolysis may cause the pH of the resulting solution to be above or below 7.00. Hydrolysis is the process whereby an ionic salt is separated into its component ions by an electric current. Both the anion and the cation of a water-soluble salt may interact with water. The ions produced by dissociation of a salt in water react with H2O. The term "hydrolysis" describes the separation of ions when an ionic compound dissolves in water.

Salt hydrolysis may cause the pH of the resulting solution to be above or below 7.00. Reason: Interaction between H2O and the ions produced by the salt results in the formation of H3O+ and/or OH- ions, impacting the solution pH. Both the anion and the cation of a water-soluble salt may interact with water. The ions produced by dissociation of a salt in water react with H2O.

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. Multiple select question. Small, highly charged metal cations accept electron pairs from water molecules and form hydrated ions. A hydrated metal ion produces an acidic solution by bonding to OH in the H2O molecules in solution. A small, highly charged metal cation can accept H+ ions from a water molecule. A hydrated metal ion produces an acidic solution because the metal ion withdraws electron density from the O-H bond, facilitating loss of H+.

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+.

An aqueous NaCl solution was found to have a pH = 7.00. Select all the statements that correctly describe this solution. Multiple select question. Only Na+ reacts with water. The NaCl solution was neutral. Neither Na+ nor Cl- reacts with water. Only Cl- reacts with water.

The NaCl solution was neutral. Reason: pH = 7.00 implies neutrality. Neither Na+ nor Cl- reacts with water. Reason: The pH is due to the autoionization of water. [H3O+] = [OH-] = 1.0 x 10-7 M; hence, pH = 7.00 (neutral).

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. Multiple select question. The pH of the Al(NO3)3 solution is 2.94. The NH4Br solution has a higher pH than the Al(NO3)3 solution. The NH4Br solution is more acidic than the Al(NO3)3 solution. The pH of the NH4Br solution is 1.12. Both solutions are equally acidic.

The pH of the Al(NO3)3 solution is 2.94. Reason: [H3O+] ≈ (1.3×10−5)×0.10‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√2(1.3×10-5)×0.102 = 1.14 × 10-3 pH = -log(1.14 × 10-3) = 2.94 The NH4Br solution has a higher pH than the Al(NO3)3 solution. Reason: The NH4+ ion is a weaker acid than the Al3+ ion. For solutions of the same concentration, the solution containing NH4+ will be less acidic with a higher pH.

A salt in which the cation is the conjugate acid of a weak base will be ______. (Assume that the anion does not hydrolyze.) Multiple choice question. neutral acidic basic

acidic

A salt consisting of a small, highly charged metal cation and the anion of a strong acid yields a(n) _____ solution. Multiple choice question. basic neutral acidic

acidic Reason: The cation acts as a weak acid, and the anion does not react.

A salt consisting of the _____ of a strong acid and the _____ of a strong base yields a neutral solution. Multiple choice question. cation; cation anion; anion anion; cation cation; anion

anion; cation

A salt in which the anion is the conjugate _____ of a weak _____ will produce a basic solution. (Assume that the cation does not hydrolyze.) Multiple choice question. acid, base base, acid

base, acid Reason: The conjugate base of a weak acid is itself a weak base. It will react with H2O to produce OH- ions and the resulting solution will be basic.

Fill in the blank question. 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

Hydrated _____ metal cations act as weak acids because these metal ions are so successful at withdrawing electron density from the O-H bond of water, thus facilitating the loss of H+ to the solvent water to form H3O+. Multiple choice question. large, weakly charged small, weakly charged small, highly charged large, highly charged

small, highly charged