Chem 175 - Chapter 16 (cont.) Exam 4

Classify as acidic, basic, or neutral NH4ClO4

Acidic

Is NH4NO3 acidic, basic, or neutral?

Acidic NH₄⁺ + H₂O ⇌ NH₃ +H₃O⁺ NH₄⁺ is the conjugate acid, so it's a weak acid NO₃⁻ is the anion of a SA, so it doesn't behave as an acid or base

Identify the Lewis acid and Lewis base in each of the reactions BF3 + F- → BF4-

BF3 = LA F- = LB

Classify as acidic, basic, or neutral K3PO4

Basic

Classify as acidic, basic, or neutral NaF

Basic

Does CH3CO2H or CH2FCO2H have a larger Ka?

CH₂FCO₂H because F is more EN

Identify each of the properties as either a characteristic of salts or not a characteristic of salts. a. compound of pos. and neg. ions b. composed of only nonmetals c. easily combustible d. contain ionic bonds e. can contain polyatomic ions f. always insoluble in water

Characteristic of Salts: a, d, and e Not a characteristic: b, c, and f

Identify the Lewis acid and Lewis base in each of the reactions Cl- + AlCl3 → AlCl4-

Cl- = LB AlCL3 = LA

Coordinate Covalent Bond

- bond in which both shared e- come from the same atom

Arrange these oxoacids (oxyacids) according to acid strength. - HBrO - HIO - HClO

Most to least: HClO, HBrO, then HIO

Which acid is the strongest? - HOCl - HOBr

HOCl since the Cl makes it more EN

Arrange these acids according to their expected pKa values. - ClCH2COOH - ClCH2CH2COOH - CH3CH2COOH - Cl2CHCOOH

Highest to lowest pKa: CH3CH2COOH, ClCH2CH2COOH, ClCH2COOH, then Cl2CHCOOH

Arrange from highest to lowest pH. - HI - RbCl - CH3NH3Br - KOH - K2CO3

Highest to lowest: KOH, K2CO3, RbCl, CH3NH3Br, then HI

Arrange these acids according to their expected pKa values. - CH3CH2COOH - Cl2CHCOOH - ClCH2CH2COOH - ClCH2COOH

Highest to lowest: CH3CH2COOH, ClCH2CH2COOH, ClCH2COOH, then Cl2CHCOOH w/ more Cl, it is more EN so more acidic, meaning the pKa is lower

Labile Hydrogen Atoms

H⁺ atoms that ionize from an acid *the stronger the chemical bond that holds a hydrogen atom, the less likely it is to break to form H⁺ ions

pKa = -log (____)

Ka

Show how triprotic acid H3PO4 ionizes in water.

Ka1: H₃PO⁴ + H₂O ⇌ H₂PO4⁻ + H₃O⁺ Ka2: H₂PO4⁻ + H₂O ⇌ HPO₄²⁻ + H₃O⁺ Ka3: HPO₄²⁻ + H₂O ⇌ PO₄³⁻ + H₃O⁺

Complete Ka1 expression for H2CO3 in an aqueous solution. H2CO3(aq) + H2O(l) ⇌ HCO−3(aq) + H3O+(aq) HCO−3(aq) + H2O(l) ⇌ CO2−3(aq) + H3O+(aq)

Ka₁ = 4.45 x 10⁻⁷ = ([H₃O⁺][HCO₃⁻]) / [H₂CO₃]

Complete Ka2 expression for H2CO3 in an aqueous solution. H2CO3(aq) + H2O(l) ⇌ HCO−3(aq) + H3O+(aq) HCO−3(aq) + H2O(l) ⇌ CO2−3(aq) + H3O+(aq)

Ka₂ = 4.69 x 10⁻¹¹ = ([CO₃²⁻][H₃O⁺]) / [HCO₃⁻]

Given that Ka for HCN is 6.2 × 10^−10 at 25 °C, what is the value of Kb for CN− at 25 °C?

Kb = 1.63 x 10⁻⁵

Given that Ka for HBrO is 2.8 × 10^−9 at 25 °C, what is the value of Kb for BrO− at 25 °C?

Kb = 3.607 x 10⁻⁶

Rank the compounds in order of decreasing acidity. - BrCH2CO2H - FCH2CO2H - ClCH2CO2H

Most to least acidic: FCH2CO2H, ClCH2CO2H, then BrCH2CO2H F is the most EN

Rank the compounds in order or decreasing acidity. - BrCH2CO2H - ClCH2CO2H - FCH2CO2H

Most to least: FCH2CO2H, ClCH2CO2H, then BrCH2CO2H F is the most EN

Identify the relative molar amounts of the species in 0.10 M NaBr(aq) from most to least. - Na+ - NaBr - H3O+ - H2O - Br- - OH-

Most to least: H2O, Na+ and Br-, H3O+ and OH-, then NaBr. [Na⁺] = [Br⁻] = 0.10M [H₃O⁺] = [OH⁻] = 1.0 x 10⁻⁷ M NaBr is insoluble, so 0 units are present

Identify the Lewis acid and Lewis base in each of the reactions NH3 + H+ → NH4+

NH3 = LB H+ = LA

Classify as acidic, basic, or neutral KCl

Neutral

Classify as acidic, basic, or neutral LiClO4

Neutral

Which anion would be the strongest base? - PO2 3- - PO3 3- - PO4 3-

PO₂³⁻

Is the anion related to a SA or WA? Cl-

SA

Is the anion related to a SA or WA? ClO4 -

SA

Is the anion related to a SA or WA? NO3 -

SA

Is this a SA, WA, SB, or WB? HI

SA

Is this a SA, WA, SB, or WB? HNO3

SA

Is this a SA, WA, SB, or WB? Ba(OH)2

SB

Is this a SA, WA, SB, or WB? CsOH

SB

Is this a SA, WA, SB, or WB? KOH

SB

Arrange the oxoacids of iodine according to strength. - HIO - HIO4 - HIO3 - HIO2

Strongest to weakest acid: HIO4, HIO3, HIO2, then HIO

Arrange the oxoacids of bromine according to strength. - HBrO - HBrO3 - HBrO4 - HBrO2

Strongest to weakest: HBrO4, HBrO3, HBrO2, then HBrO

Is the anion related to a SA or WA? CO3 2-

WA

Is the anion related to a SA or WA? PO4 3-

WA

Is the anion related to a SA or WA? S 2-

WA

Is this a SA, WA, SB, or WB? H3PO4

WA

Is this a SA, WA, SB, or WB? HCN

WA

Is this a SA, WA, SB, or WB? HN3

WA

Is this a SA, WA, SB, or WB? NH4Cl

WA

Is this a SA, WA, SB, or WB? (CH3)3N

WB

Is this a SA, WA, SB, or WB? CH3NH2

WB

Is this a SA, WA, SB, or WB? Na3PO4

WB

Calculate the concentrations of all species in a 0.600 M NaCH3COO (sodium acetate) solution. The ionization constant for acetic acid is Ka = 1.8×10−5 . #15 of HW 10

[Na⁺] = [CH₃COO⁻] = 0.6 [OH⁻] = [CH₃COOH] = 1.83 x 10⁻⁵ [H₃O⁺] = 5.50 x 10⁻¹⁰ *use ice table, assume that [OH-] initially = 10⁻⁷ x = 1.8 x 10⁻⁵

A Lewis acid is an e- __________.

acceptor

A Brønsted-Lowry ____ is a proton (H+) donor

acid

What is the principal difference between a strong acid and a weak acid? a. When neutralized, strong acids form salt and water while weak acids only form water. b. Strong acids completely ionize while weak acids only partially ionize. c. Strong acids are polyprotic while weak acids are monoprotic. d. Strong acids have high concentrations of the hydroxide ion while in solution.

b

A Brønsted-Lowry ____ is a proton (H+) acceptor

base

Which of the choices is the Lewis definition of acids and bases? a. An acid is a sub. that contains H and ionizes to produce H ions in aqueous solution. A base is a substance that contains a OH- group and dissociates to produce a OH- ion in aqueous solution b. An acid is a hydrogen-ion donor and a base is a hydrogen-ion acceptor c. An acid is any substance that can donate a lone pair of e-, and a base is any substance that can accept a lone pair of e- d. An acid is any species that can accept a lone pair of e-, and a base is any species that can donate a lone pair of e-

d

As the bond enthalpy increases, the pKa __________.

decreases

A Lewis base is an e- _________.

donor

A lower pH has a (lower or higher) Ka?

higher

As the anion size increase (anion size decreases), the pKa _________.

increases

____ = 1/2 (pKa1 + pKa2)

pH

Calculate the pH of a 0.112 M solution of ethylenediamine (H2NCH2CH2NH2). The pKa values for the acidic form of ethylenediamine (H3+NCH2CH2NH3+) are 6.848 (pKa1) and 9.928(pKa2). Calculate the concentration of each form of ethylenediamine in this solution at equilibrium.

pH = 11.49 [H2NCH2CH2NH2] = 0.109 [H2NCH2CH2NH3+] = 3.09 x 10^-3 [H3+NCH2CH2NH3+] = 7.04 x 10^-8

Ascorbic acid (H2C6H6O6) is a diprotic acid. The acid dissocation constants for H2⁢C6⁢H6⁢O6 are Ka1=8.00×10−5 and Ka2=1.60×10−12 1. Determine the pH of a 0.141 M solution of ascorbic acid. 2. Determine the equilibrium concentrations of all species in the solution.

pH = 2.47 [H2C6H6O6] = 0.1376 [HC6H6O6⁻] = 3.36 x 10⁻³ [C6H6O6²⁻] = 1.60 x 10⁻¹² *use ice tables

CH3⁢NH2 is a weak base (Kb = 5.0 × 10^−4), so the salt CH3⁢NH3⁢NO3 acts as a weak acid. What is the pH of a solution that is 0.0650 M in CH3⁢NH3⁢NO3 at 25 ∘C?

pH = 5.94 *use ice table, convert to Ka Ka = 2.0 x 10⁻¹¹

Calculate the pH of a 0.411 M solution of NaF. The Ka for the weak acid HF is 6.8 × 10−4.

pH = 8.39 F⁻ + H₂O ⇌ HF + OH⁻ *convert to Kb to solve, then use ice table

A _____ is a compound without H+ as the cation or OH- as the anion.

salt