AcidsAcids Strong Acids: Strong Acids: Two types of strong acids, with Two types of strong acids, with

examples that examples that you should memorizeyou should memorize, are, are 1.The hydrohalic acids HCl, HBr, and HI1.The hydrohalic acids HCl, HBr, and HI 2.Oxoacids in which the number of O atoms exceeds the 2.Oxoacids in which the number of O atoms exceeds the

number of ionizable protons by two or more, such as HNOnumber of ionizable protons by two or more, such as HNO33, , HH22SOSO44, and HClO, and HClO44; for example, in H; for example, in H22SOSO44, 4 O’s − 2H’s = 2, 4 O’s − 2H’s = 2

Weak acids: Weak acids: There are many There are many moremore weak acids weak acids than strong ones. Four types, with examples, than strong ones. Four types, with examples, areare 1.The hydrohalic acid HF1.The hydrohalic acid HF 2.Acids in which H is not bonded to O or to a halogen, such 2.Acids in which H is not bonded to O or to a halogen, such

as HCN and Has HCN and H22SS 3.Oxoacids in which the number of O atoms equals or 3.Oxoacids in which the number of O atoms equals or

exceeds by one the number of ionizable protons, such as exceeds by one the number of ionizable protons, such as HClO, HNOHClO, HNO22, and H, and H33POPO44

4.Carboxylic acids (general formula RCOO4.Carboxylic acids (general formula RCOOHH, with the , with the ionizable proton shown in red), such as CH3COOionizable proton shown in red), such as CH3COOHH and and C6H5COOC6H5COOHH

BasesBases Strong bases: Strong bases: Water-soluble compounds Water-soluble compounds

containing Ocontaining O2−2− or OH− ions are strong or OH− ions are strong bases. The cations are usually those of the bases. The cations are usually those of the most active metals:most active metals: 1.M1.M22O or MOH, where M = Group 1A(1) metal (Li, Na, K, O or MOH, where M = Group 1A(1) metal (Li, Na, K,

Rb, Cs)Rb, Cs) 2.MO or M(OH)2.MO or M(OH)22, where M = Group 2A(2) metal (Ca, Sr, , where M = Group 2A(2) metal (Ca, Sr,

Ba) [MgO and Mg(OH)Ba) [MgO and Mg(OH)22 are only slightly soluble in water, are only slightly soluble in water, but the soluble portion dissociates completely.]but the soluble portion dissociates completely.]

Weak bases: Weak bases: Many compounds with an Many compounds with an electron-rich nitrogen atom are weak bases electron-rich nitrogen atom are weak bases (none are Arrhenius bases). The common (none are Arrhenius bases). The common structural feature is an N atom with a lone structural feature is an N atom with a lone electron pair:electron pair: 1.Ammonia 1.Ammonia 2.Amines R-NH22.Amines R-NH2

Bronsted-Lowry Acid-Base Bronsted-Lowry Acid-Base ModelModel

This model focuses on the nature of acids and This model focuses on the nature of acids and bases and the reactions between them.bases and the reactions between them.

Definitions:Definitions:Acid – proton (H+ ion) donorAcid – proton (H+ ion) donorBase – proton (H+ ion) acceptorBase – proton (H+ ion) acceptor

In an acid-base reaction, a proton is transferred In an acid-base reaction, a proton is transferred from an acid to a base:from an acid to a base:

HB + AHB + A-- ⇌⇌ HA + B HA + B--

Conjugate base: the species formed when a Conjugate base: the species formed when a proton is removed from the acid.proton is removed from the acid.

Conjugate acid: the species formed when a Conjugate acid: the species formed when a proton is added to a base.proton is added to a base.

Conjugate Acids & BasesConjugate Acids & Bases HH22S + NHS + NH33 ⇌ HS ⇌ HS−− + NH + NH44++

Example 1: For the equation above list the Bronsted-Lowry Acids and Example 1: For the equation above list the Bronsted-Lowry Acids and BasesBases

Ans: Acids - HAns: Acids - H22S, NHS, NH44++ Bases - HS Bases - HS--, NH, NH33

Example 2: For the substances below list the B-L BasesExample 2: For the substances below list the B-L Bases Conjugate AcidConjugate Acid Conjugate BaseConjugate Base

HFHF ----Ans: FAns: F--

HSOHSO44-- ----

Ans: SOAns: SO442-2-

NHNH44+ + ----

Ans: NHAns: NH33

AmphiproticAmphiprotic A species that can either accept or donate a A species that can either accept or donate a

proton.proton. For example: Water is amphiprotic: For example: Water is amphiprotic: 

HH22O + HO + H22O ⇌ HO ⇌ H33OO+ + + OH + OH--

Example 3: Example 3:

What is the conjugate acid and base forWhat is the conjugate acid and base for The bicarbonate ion The bicarbonate ion

Ans: HAns: H22COCO33, CO, CO332-2-

Hydrogen sulfate ion Hydrogen sulfate ion Ans: HAns: H22S, SS, S2-2-

The Ion Product of The Ion Product of Water:Water:

The ionization of water can be The ionization of water can be simplified to the ionization of one simplified to the ionization of one water molecule: water molecule: 

HH22O ⇌ HO ⇌ H++ (aq)(aq) + OH + OH-- (aq)(aq)

The ion product constant of water @ The ion product constant of water @ 25⁰C:25⁰C:

KKww = [H = [H++] [OH] [OH--] = 1.0 x 10] = 1.0 x 10-14-14

Ion Product Concentration of Ion Product Concentration of WaterWater

The concentrations of HThe concentrations of H++ (H (H++ = H = H33OO++) and ) and OHOH-- ions are can be calculated from the K ions are can be calculated from the Kww in pure water @ 25⁰Cin pure water @ 25⁰C

When the HWhen the H++ ions equal the OH ions equal the OH-- ions the ions the solution is said to be a neutral solution:solution is said to be a neutral solution: If [H+] is > 1.0 x 10If [H+] is > 1.0 x 10-7-7, [OH-] < 1.0 x 10, [OH-] < 1.0 x 10-7-7 solution is acidicsolution is acidic If [OH-] is > 1.0 x 10If [OH-] is > 1.0 x 10-7-7, [H+] < 1.0 x 10, [H+] < 1.0 x 10-7-7 solution is basicsolution is basic

These 2 quantities have an inversely These 2 quantities have an inversely proportional relationshipproportional relationship

pHpH This is an alternative method for specifying the acidity of This is an alternative method for specifying the acidity of

a solution. a solution.  pH stands for the power of the hydrogen ion and can be pH stands for the power of the hydrogen ion and can be

found using the following: found using the following: 

pH = -log[HpH = -log[H++] = -log[H] = -log[H33OO++]]

or  the same formula can be used to determine the [H+] concentration by: or  the same formula can be used to determine the [H+] concentration by: [H[H++] = 10] = 10-pH-pH

Determining acidic or basic:Determining acidic or basic: Acidic = Acidic = pH < 7, the lower the # the more acidic the pH < 7, the lower the # the more acidic the

solutionsolution Basic = Basic = pH > 7, the higher the # the more basic the pH > 7, the higher the # the more basic the

solutionsolution Neutral = pH = 7Neutral = pH = 7

pOHpOH A similar approach is used to A similar approach is used to

determine the hydroxide ion determine the hydroxide ion concentration:concentration:

pOH = -log[OHpOH = -log[OH--]] Because [H+] [OH-] = 1.0 x 10Because [H+] [OH-] = 1.0 x 10-14-14 then then

the pH and pOH are connected by the the pH and pOH are connected by the following: following: 

pH + pOH = 14.00pH + pOH = 14.00

Calculating pH and pOHCalculating pH and pOH Example 4: At 25 Example 4: At 25 ooC, calculateC, calculate

the hydrogen ion concentration and pH of a tap-the hydrogen ion concentration and pH of a tap-water sample in which the hydroxide ion water sample in which the hydroxide ion concentration is 2.0 x 10concentration is 2.0 x 10-7-7. .

Ans: 5.0 x 10Ans: 5.0 x 10-8-8MM The hydrogen and hydroxide ion concentrations of The hydrogen and hydroxide ion concentrations of

human blood at a pH of 7.40. human blood at a pH of 7.40. Ans: 4.0 x 10Ans: 4.0 x 10-8-8M, 2.5 x 10M, 2.5 x 10-7-7MM

The pOH of a solution in which the [HThe pOH of a solution in which the [H++] = ] = 5.0[OH5.0[OH--]. ].

Ans: 7.35Ans: 7.35

Strong Acids & BasesStrong Acids & Bases

The pH of strong acids and bases The pH of strong acids and bases ionize completely in water and ionize completely in water and because of this it is relatively easy to because of this it is relatively easy to determine the pH and pOH.determine the pH and pOH.

Example 5: What is the pH of a Example 5: What is the pH of a solution prepared by dissolving 1.00 solution prepared by dissolving 1.00 g of barium hydroxide per liter?g of barium hydroxide per liter? Ans: 12.07Ans: 12.07

Weak Acids & Their Equilibrium Weak Acids & Their Equilibrium ConstantsConstants

Weak acids react reversibly with water to form H+ Weak acids react reversibly with water to form H+ ions.ions.

Most weak acids fall into two categories:Most weak acids fall into two categories: 1. Molecules containing an ionizable hydrogen atom:1. Molecules containing an ionizable hydrogen atom:

HNOHNO22 (aq) + H (aq) + H22O O ⇌⇌ H H33OO++ (aq) + NO (aq) + NO22-- (aq) (aq)

2. Cations. The ammonium ion acts as a weak acid in 2. Cations. The ammonium ion acts as a weak acid in water.water.

NHNH44++ (aq) + H (aq) + H22O O ⇌⇌ H H33OO++ (aq) + NH (aq) + NH33 (aq) (aq)

Many metal cations actually act as weak acids: Al(HMany metal cations actually act as weak acids: Al(H22O)O)66+3+3

KKaa

The equilibrium constant for a weak The equilibrium constant for a weak acid:acid:

HX ⇌ HHX ⇌ H++ + X + X--

KKaa = =[H+] [X-][H+] [X-]

[HX][HX]

*the smaller the Ka value the weaker *the smaller the Ka value the weaker the acid.the acid.

pKpKaa We sometimes use a pKa value for weak acids: We sometimes use a pKa value for weak acids:

pKpKaa = -logK = -logKaa The larger the pKa the weaker the acid. The larger the pKa the weaker the acid.  Example 6: consider acetic acid (kExample 6: consider acetic acid (kaa=1.8 x 10=1.8 x 10-5-5) and the ) and the

tetraaquazinc(II) ion (ktetraaquazinc(II) ion (kaa=3.3 x 10=3.3 x 10-10-10) .) . Write the equations to show why these species are Write the equations to show why these species are

acidic.acidic. Which is the stronger acid? Which is the stronger acid?

Ans: acetic acidAns: acetic acid What is the pKWhat is the pKaa of the tetraaquazinc ion? of the tetraaquazinc ion?

Ans: 9.48Ans: 9.48

Calculating KCalculating Kaa using an equilibrium using an equilibrium table…table…

Example 7: Aspirin is a weak organic Example 7: Aspirin is a weak organic acid whose molecular formula maybe acid whose molecular formula maybe written as HCwritten as HC99HH77OO44. A water solution . A water solution of aspirin is prepared by dissolving of aspirin is prepared by dissolving 3.60 g per liter. The pH of the 3.60 g per liter. The pH of the solution is found to be 2.60. solution is found to be 2.60. Calculate the KCalculate the Kaa for aspirin. for aspirin. Ans: 3.6 x 10Ans: 3.6 x 10-4-4

% Ionization% Ionization

Percent Ionization allows us to measure Percent Ionization allows us to measure the percent of H+ ion that are ionized:the percent of H+ ion that are ionized:

% ionization =% ionization = [H+][H+] x 100 x 100 [HX] [HX]

Example 8: What percent of H+ ions Example 8: What percent of H+ ions from the aspirin ionized in the previous from the aspirin ionized in the previous example?example? Ans: 12%Ans: 12%

Example 9Example 9

Nicotinic acid, HCNicotinic acid, HC66HH44OO22N (KN (Kaa = 1.4 x = 1.4 x 1010-5-5), is another name for niacin, an ), is another name for niacin, an important member of the vitamin B important member of the vitamin B group. Determine the [Hgroup. Determine the [H++] in a ] in a solution prepared by dissolving 0.10 solution prepared by dissolving 0.10 mol of nicotinic acid, HNic, in water mol of nicotinic acid, HNic, in water to form one liter of solution.to form one liter of solution. [H[H++] = 1.2 x 10] = 1.2 x 10-3-3 M M

Polyprotic Weak AcidsPolyprotic Weak Acids

These are acids that have more than one These are acids that have more than one ionizable hydrogen ion. These acids ionize ionizable hydrogen ion. These acids ionize in steps, with a separate equilibrium in steps, with a separate equilibrium constant for each one: constant for each one: HH22CC22OO44 (aq) (aq) ⇌⇌ H H++ (aq) + HC (aq) + HC22OO44

-- KKa1a1 = 5.9 x 10 = 5.9 x 10-2-2

HCHC22OO44-- (aq) (aq) ⇌⇌ H H++ (aq) + C (aq) + C22OO44

-2-2 KKa2a2 = 5.2 x 10 = 5.2 x 10-5-5

The anion formed in step one produces The anion formed in step one produces another H+ ion in the next step.another H+ ion in the next step.

The Ka becomes smaller with each The Ka becomes smaller with each successive step:successive step:

KKa1a1 > K > Ka2 a2 > K > Ka3a3

Calculating pH of a polyprotic acidCalculating pH of a polyprotic acid

Example 10: The distilled water you Example 10: The distilled water you use in the laboratory is slightly acidic use in the laboratory is slightly acidic because of dissolved carbon dioxide, because of dissolved carbon dioxide, which reacts to form carbonic acid. which reacts to form carbonic acid. Calculate the pH of a 0.0010 M Calculate the pH of a 0.0010 M solution of carbonic acid (Ksolution of carbonic acid (Ka1a1 = 4.4 x = 4.4 x 1010-7-7, K, Ka2a2 = 4.7 x 10 = 4.7 x 10-11-11).). Ans: 4.68Ans: 4.68

Weak Bases & Their Weak Bases & Their Equilibrium ConstantsEquilibrium Constants

Most weak bases, like acids, fall into Most weak bases, like acids, fall into two categories:two categories: 1. Molecules, including organic 1. Molecules, including organic

compounds known as amines:compounds known as amines:NHNH33 (aq)(aq) + H + H22O O ⇌⇌ NH NH44

++ (aq)(aq) + OH + OH-- (aq)(aq)

2. Anion. An anion derived from a weak 2. Anion. An anion derived from a weak acid is itself a weak base:acid is itself a weak base:

F- F- (aq)(aq) + H + H22O O ⇌⇌ HF HF (aq)(aq) + OH + OH- - (aq)(aq)

Weak BasesWeak Bases

Example 11: Write an equation to Example 11: Write an equation to explain why each of the following explain why each of the following produces a basic water solution.produces a basic water solution. NONO22--

NaNa22COCO33

KHCOKHCO33

Calculation of [OH-]Calculation of [OH-]

Example 12: Calculate the pH of a Example 12: Calculate the pH of a 0.10 M NaF (K0.10 M NaF (Kbb = 1.4 x 10 = 1.4 x 10-11-11).). Ans: 8.08Ans: 8.08

KKaa and K and Kbb

The KThe Kaa of a weak acid and the K of a weak acid and the Kbb of a of a weak base will equal Kw:weak base will equal Kw:

The stronger the The stronger the acid the weaker acid the weaker its conjugate its conjugate base and vice base and vice versa for bases.versa for bases.

Acid-Base Properties of Acid-Base Properties of SolutionsSolutions A salt is an ionic solid containing a cation other A salt is an ionic solid containing a cation other

than H+ and an anion other than OH-.than H+ and an anion other than OH-. It is important to remember that anions of strong It is important to remember that anions of strong

acids and cations of strong bases are neutral in acids and cations of strong bases are neutral in solution.solution. All other cations will be acidic in nature.All other cations will be acidic in nature. All other anions will be basic in nature.All other anions will be basic in nature.

To predict whether a given salt solution will be To predict whether a given salt solution will be acidic, basic, or neutral, consider the three factors:acidic, basic, or neutral, consider the three factors: 1. Decide what effect, if any, the cation has on the pH of 1. Decide what effect, if any, the cation has on the pH of

water.water. 2. Decide what effect, if any, the anion will have on the pH 2. Decide what effect, if any, the anion will have on the pH

of water.of water. 3. Combine the 2 effects to decide the behavior of the salt.3. Combine the 2 effects to decide the behavior of the salt.

If both cation and anion have a K value, the one with the If both cation and anion have a K value, the one with the larger value decides acidic or basic.larger value decides acidic or basic.

Salts: Acidic, Basic, Neutral?Salts: Acidic, Basic, Neutral? Example 13: Consider water solutions of the Example 13: Consider water solutions of the

following six salts and identify if the solution are following six salts and identify if the solution are acidic, basic, or neutral: acidic, basic, or neutral: Ammonium iodide Ammonium iodide

Ans: acidicAns: acidic Zinc nitrateZinc nitrate

Ans: acidicAns: acidic Potassium perchloratePotassium perchlorate

Ans: neutralAns: neutral Sodium phosphateSodium phosphate

Ans: basicAns: basic Ammonium fluorideAmmonium fluoride

Ans: acidicAns: acidic Ammonium hypochlorite Ammonium hypochlorite

Ans: basicAns: basic

MC #1MC #1

Which of the following ions is the Which of the following ions is the strongest Lewis acid?strongest Lewis acid?

(A) Na(A) Na++

(B) Cl¯(B) Cl¯(C) CH3COO¯(C) CH3COO¯(D) Mg(D) Mg2+2+

(E) Al(E) Al3+3+

MC #2MC #2

Each of the following can act as both Each of the following can act as both a Brönsted acid and a Brönsted base a Brönsted acid and a Brönsted base EXCEPTEXCEPT

(A) HCO(A) HCO33¯̄(B) H(B) H22POPO44¯̄(C) NH(C) NH44++

(D) H(D) H22OO(E) HS¯ (E) HS¯

MC #3MC #3

Which, if any, of the following species is in Which, if any, of the following species is in the greatest concentration in a 0.100-the greatest concentration in a 0.100-molar solution of Hmolar solution of H22SOSO44 in water? in water?

(A) H(A) H22SOSO44 molecules molecules(B) H(B) H33OO++ ions ions(C) HSO(C) HSO44¯ ions¯ ions(D) SO(D) SO442¯2¯ ions ions(E) All species are in equilibrium and (E) All species are in equilibrium and therefore have the same concentrations. therefore have the same concentrations.

MC #4MC #4

Which of the following reactions does NOT Which of the following reactions does NOT proceed significantly to the right in proceed significantly to the right in aqueous solutions?aqueous solutions?

(A) H(A) H33O+ + OH¯ ---> 2 HO+ + OH¯ ---> 2 H22OO(B) HCN + OH¯ ---> H(B) HCN + OH¯ ---> H22O + CN¯O + CN¯(C) Cu(H(C) Cu(H22O)O)442+2+ + 4 NH + 4 NH33 ---> Cu(NH ---> Cu(NH33))442+2+ + + 4H4H22OO(D) H(D) H22SOSO44 + H + H22O ---> HO ---> H33O+ + HSOO+ + HSO44¯̄(E) H(E) H22O + HSOO + HSO44¯ ---> H¯ ---> H22SOSO44 + OH¯ + OH¯

MC #5MC #5

If the acid dissociation constant, Ka, for an If the acid dissociation constant, Ka, for an acid HA is 8 x 10acid HA is 8 x 10¯4¯4 at 25 °C, what percent at 25 °C, what percent of the acid is dissociated in a 0.50-molar of the acid is dissociated in a 0.50-molar solution of HA at 25 °C?solution of HA at 25 °C?

(A) 0.08%(A) 0.08%(B) 0.2%(B) 0.2%(C) 1%(C) 1%(D) 2%(D) 2%(E) 4% (E) 4%

MC #6MC #6

All of the following species can All of the following species can function as Brönsted-Lowry bases in function as Brönsted-Lowry bases in solution EXCEPTsolution EXCEPT

(A) H(A) H22OO(B) NH(B) NH33

(C) S(C) S2¯2¯

(D) NH(D) NH44++

(E) HCO(E) HCO33¯ ¯

MC #7MC #7 As the number of oxygen atoms increases As the number of oxygen atoms increases

in any series of oxygen acids, such as in any series of oxygen acids, such as HXO, HXO2, HXO3, ...., which of the HXO, HXO2, HXO3, ...., which of the following is generally true?following is generally true?(A) The acid strength varies unpredictably.(A) The acid strength varies unpredictably.(B) The acid strength decreases only if X is (B) The acid strength decreases only if X is a nonmetal.a nonmetal.(C) The acid strength decreases only if X is (C) The acid strength decreases only if X is a metal.a metal.(D) The acid strength decreases whether X (D) The acid strength decreases whether X is a nonmetal or a metal.is a nonmetal or a metal.(E) The acid strength increases.(E) The acid strength increases.

MC #8MC #8

A 0.20-molar solution of a weak A 0.20-molar solution of a weak monoprotic acid, HA, has a pH of 3.00. monoprotic acid, HA, has a pH of 3.00. The ionization constant of this acid is The ionization constant of this acid is

(A) 5.0 x 10(A) 5.0 x 10¯7¯7

(B) 2.0 x 10(B) 2.0 x 10¯7¯7

(C) 5.0 x 10(C) 5.0 x 10¯6¯6

(D) 5.0 x 10(D) 5.0 x 10¯3¯3

(E) 2.0 x 10(E) 2.0 x 10¯3¯3

MC #9MC #9 HSOHSO44¯ + H¯ + H22O <===> HO <===> H33OO++ + SO + SO442–2–

In the equilibrium represented above, the species In the equilibrium represented above, the species that act as bases include which of the following? that act as bases include which of the following?

I. HSOI. HSO44¯̄II. HII. H22OOIII. III. SOSO442–2–

(A) II only(A) II only(B) III only(B) III only(C) I and II(C) I and II(D) I and III(D) I and III(E) II and III (E) II and III

MC #10MC #10

HH22CC22OO44 + 2H + 2H22O <===> 2HO <===> 2H33OO++ + C + C22OO442¯2¯ Oxalic acid, HOxalic acid, H22CC22OO44, is a diprotic acid with K, is a diprotic acid with K11 = 5 x 10= 5 x 10¯2¯2 and K and K22 = 5 x 10 = 5 x 10¯5¯5. Which of the . Which of the following is equal to the equilibrium following is equal to the equilibrium constant for the reaction represented constant for the reaction represented above?above?(A) 5 x 10(A) 5 x 10¯2¯2

(B) 5 x 10(B) 5 x 10¯5¯5

(C) 2.5 x 10(C) 2.5 x 10¯6¯6

(D) 5 x 10(D) 5 x 10¯7¯7

(E) 2.5 x 10(E) 2.5 x 10¯8¯8

MC #11MC #11

A 1-molar solution of which of the A 1-molar solution of which of the following salts has the highest pH ?following salts has the highest pH ?

(A) NaNO(A) NaNO33

(B) Na(B) Na22COCO33

(C) NH(C) NH44ClCl(D) NaHSO(D) NaHSO44

(E) Na(E) Na22SOSO44

MC #12MC #12

What is the pH of a 1.0 x 10What is the pH of a 1.0 x 10¯2¯2 M M solution of HCN? (Ka = 4.0 x 10solution of HCN? (Ka = 4.0 x 10¯10¯10.).)

(A) 10(A) 10(B) Between 7 and 10(B) Between 7 and 10(C) 7(C) 7(D) Between 4 and 7(D) Between 4 and 7(E) 4 (E) 4

MC #13MC #13 The net ionic equation for the reaction that The net ionic equation for the reaction that

occurs during the titration of nitrous aicd occurs during the titration of nitrous aicd with sodium hydroxide is with sodium hydroxide is

(A) HNO(A) HNO22 + Na + Na++ + OH¯ ---> NaNO + OH¯ ---> NaNO22 + H + H22OO(B) HNO(B) HNO22 + NaOH ---> Na + NaOH ---> Na++ + NO + NO22¯ + H¯ + H22OO(C) H(C) H++ + OH¯ --->H + OH¯ --->H22OO(D) HNO(D) HNO22 + H + H22O ---> NOO ---> NO22¯ + H¯ + H33OO++

(E) HNO(E) HNO22 + OH¯ ---> NO + OH¯ ---> NO22¯ + H¯ + H22OO

MC #14MC #14

What is the HWhat is the H+ + (aq)(aq) concentration in concentration in 0.05 M HCN 0.05 M HCN (aq)(aq)? (The K? (The Kaa for HCN is for HCN is 5.0 x 105.0 x 10¯10¯10) )

(A) 2.5 x 10(A) 2.5 x 10¯11¯11

(B) 2.5 x 10(B) 2.5 x 10¯10¯10

(C) 5.0 x 10(C) 5.0 x 10¯10¯10

(D) 5.0 x 10(D) 5.0 x 10¯6¯6

(E) 5.0 x 10(E) 5.0 x 10¯4¯4

MC #15MC #15

A molecule or an ion is classified as a Lewis A molecule or an ion is classified as a Lewis acid if it acid if it

(A) accepts a proton from water(A) accepts a proton from water(B) accepts a pair of electrons to form a (B) accepts a pair of electrons to form a bondbond(C) donates a pair of electrons to form a (C) donates a pair of electrons to form a bondbond(D) donates a proton to water(D) donates a proton to water(E) has resonance Lewis electron-dot (E) has resonance Lewis electron-dot structures structures

FRQ #1FRQ #1A pure 14.85 g sample of the weak base ethylamine, CA pure 14.85 g sample of the weak base ethylamine, C22HH55NHNH22 , is , is dissolved in enough distilled water to make 500. mL of solution.dissolved in enough distilled water to make 500. mL of solution.

(a)(a) Calculate the molar concentration of the CCalculate the molar concentration of the C22HH55NHNH22 in the in the solution.solution.

The aqueous ethylamine reacts with water according to the The aqueous ethylamine reacts with water according to the equation below.equation below.

CC22HH55NHNH22(aq)(aq) + H + H22OO(l)(l) C C22HH55NHNH33++(aq)(aq) + OH- + OH-(aq)(aq) (b)(b) Write the equilibrium-constant expression for the reaction Write the equilibrium-constant expression for the reaction

between Cbetween C22HH55NHNH22(aq)(aq) and water. and water. (c)(c) Of COf C22HH55NHNH22(aq)(aq) and C and C22HH55NHNH33++(aq)(aq), which is present in the , which is present in the

solution at the higher concentration at equilibrium? Justify solution at the higher concentration at equilibrium? Justify your your answer.answer.

*(d)*(d) A different solution is made by mixing 500. mL of 0.500 A different solution is made by mixing 500. mL of 0.500 M M CC22HH55NHNH2 2 with 500. mL of 0.200 with 500. mL of 0.200 M M HCl. Assume that volumes HCl. Assume that volumes are additive. The pH of the resulting solution is found to be are additive. The pH of the resulting solution is found to be

10.93.10.93. (i) Calculate the concentration of OH-(i) Calculate the concentration of OH-(aq)(aq) in the solution. in the solution. (ii) Write the net-ionic equation that represents the reaction that occurs (ii) Write the net-ionic equation that represents the reaction that occurs

when the Cwhen the C22HH55NHNH22 solution is mixed with the HCl solution. solution is mixed with the HCl solution. (iii) Calculate the molar concentration of the C(iii) Calculate the molar concentration of the C22HH55NHNH33++(aq)(aq) that is that is

formed in the reaction.formed in the reaction. (iv) Calculate the value of (iv) Calculate the value of Kb Kb for Cfor C22HH55NHNH22..

FRQ #2FRQ #2HFHF(aq)(aq) + H + H22OO(l)(l) H H33OO++(aq)(aq) + F–+ F–(aq)(aq) KKaa = = 7.2×10–47.2×10–4Hydrofluoric acid, HF, dissociates in water as represented Hydrofluoric acid, HF, dissociates in water as represented by the equation above. by the equation above.

(a)(a) Write the equilibrium-constant expression for the Write the equilibrium-constant expression for the dissociation of HF in water. dissociation of HF in water.

(b)(b) Calculate the molar concentration of HCalculate the molar concentration of H33O+ in a O+ in a 0.40 0.40 M M HF solution. HF solution.

HFHF(aq)(aq) reacts with NaOH reacts with NaOH(aq)(aq) according to the reaction according to the reaction represented below.represented below.

HFHF(aq)(aq) + OH– + OH–(aq)(aq) H H22OO(l)(l) + F– + F–(aq)(aq)

A volume of 15 mL of 0.40 A volume of 15 mL of 0.40 M M NaOHNaOH(aq)(aq) is added to 25 mL is added to 25 mL of 0.40 of 0.40 M M HFHF(aq)(aq) solution. Assume that volumes are solution. Assume that volumes are additive.additive.

*(c)*(c) Calculate the number of moles of HFCalculate the number of moles of HF(aq)(aq) remaining remaining in the solution.in the solution.

(d)(d) Calculate the molar concentration of F–Calculate the molar concentration of F–(aq)(aq) in the in the solution. solution.

(e)(e) Calculate the pH of the solution. Calculate the pH of the solution.

FRQ #3FRQ #3HCHC33HH55OO22(aq)(aq) ↔ C ↔ C33HH55OO22– – (aq)(aq) + H + H++(aq)(aq) KKaa = 1.34 x 10 = 1.34 x 10–5–5

Propanoic acid, HCPropanoic acid, HC33HH55OO22, ionizes in water according to the equation , ionizes in water according to the equation above.above.

(a)(a) Write the equilibrium constant expression for the reaction.Write the equilibrium constant expression for the reaction. (b)(b) Calculate the pH of a 0.265 Calculate the pH of a 0.265 MM solution of propanoic acid. solution of propanoic acid. (c)(c) A 0.496 g sample of sodium propanoate, NaCA 0.496 g sample of sodium propanoate, NaC33HH55OO22, is added to , is added to

a 50.0 mL sample of a 0.265 M solution of propanoic acid. Assuming a 50.0 mL sample of a 0.265 M solution of propanoic acid. Assuming that no change in the volume of the solution occurs, calculate each of that no change in the volume of the solution occurs, calculate each of the following.the following. (i) The concentration of the propanoate ion, C(i) The concentration of the propanoate ion, C33HH55OO22––(aq)(aq) in the solution in the solution (ii) The concentration of the H(ii) The concentration of the H++(aq)(aq) ion in the so lution. ion in the so lution.

The methanoate ion, HCOThe methanoate ion, HCO22––(aq)(aq) reacts with water to form methanoic reacts with water to form methanoic acid and hydroxide ion, as shown in the following equation.acid and hydroxide ion, as shown in the following equation.

HCOHCO22––(aq)(aq) + H + H22OO (l)(l) ↔ H ↔ H22COCO22(aq)(aq) + OH– + OH–(aq)(aq)

*(d)*(d) Given that [OH–] is 4.18 x 10Given that [OH–] is 4.18 x 10–6–6 MM in a 0.309 in a 0.309 MM solution of solution of sodium methanoate, calculate each of the following.sodium methanoate, calculate each of the following. (i) The value of (i) The value of KKbb for the methanoate ion, HCO for the methanoate ion, HCO22––(aq)(aq) (ii) The value of (ii) The value of KKaa for methanoic acid, HCO for methanoic acid, HCO22HH

*(e)*(e) Which acid is stronger, propanoic acid or methanoic acid? Which acid is stronger, propanoic acid or methanoic acid? Justify yourJustify your answer. answer.

FRQ #4FRQ #4Hypochlorous acid, HOCl, is a weak acid Hypochlorous acid, HOCl, is a weak acid commonly used as a bleaching agent. The acid–commonly used as a bleaching agent. The acid–dissociation constant, dissociation constant, Ka, Ka, for the reaction for the reaction represented above is 3.2×10represented above is 3.2×10–8–8..

(a)(a) Calculate the [H+] of a 0.14–molar Calculate the [H+] of a 0.14–molar solution of HOCl.solution of HOCl.

(b)(b) Write the correctly balanced net ionic Write the correctly balanced net ionic equation for the reaction that occurs when equation for the reaction that occurs when NaOCl is dissolved in water and calculate the NaOCl is dissolved in water and calculate the numerical value of the equilibrium constant for numerical value of the equilibrium constant for the reaction.the reaction.

*(c) Calculate the pH of a solution made by *(c) Calculate the pH of a solution made by combining 40.0 milliliters of 0.14–molar HOCl combining 40.0 milliliters of 0.14–molar HOCl and 10.0 milliliters of 0.56–molar NaOH.and 10.0 milliliters of 0.56–molar NaOH.

FRQ #5FRQ #5Give a brief explanation for each of the Give a brief explanation for each of the following.following.

(a)(a) For the diprotic acid HFor the diprotic acid H22S, the first S, the first dissociation constant is larger than the dissociation constant is larger than the second dissociation constant by about 10second dissociation constant by about 1055 (K(K11 ~ 10 ~ 1055 K K22).).

(b)(b) In water, NaOH is a base but HOCl is In water, NaOH is a base but HOCl is an acid.an acid.

(c)(c) HCl and HI are equally strong acids in HCl and HI are equally strong acids in water but, in pure acetic acid, HI is a water but, in pure acetic acid, HI is a stronger acid than HCl.stronger acid than HCl.

(d)(d) When each is dissolved in water, HCl When each is dissolved in water, HCl is a much stronger acid than HF.is a much stronger acid than HF.