Chem 2 Exam 3 Chapter 15 MC

The conjugate base of formic acid, HCOOH, is _____. OH - CH3 COO - HCOO - CO22-

C) HCOO -

An example of a strong acid is _____. A) CH3COOH B) HCN C) H2CO3 D) HClO4

HClO4

Which acid below is the strongest acid? a. HClO4 b. HClO3 c. H2SO4 d. HNO3

HClO4

Which of the following is a weak acid? a. H2SO4 b. HF c. HBr d. HI

HF

Which acid in the list below is the strongest acid? a. H2S b. HI c. HCl d. HBr

HI HCl, HBr, and HI are all strong acids in water, however since Iodide has a larger radius, it is least able to hold onto its hydrogen ions making it the strongest acid.

1. The dihydrogen phosphate ion undergoes these reactions in water. H2PO4- + H2O ↔ HPO42- + H3O+ K = 6.2 x 10-8 H2PO4- + H2O ↔ H3PO4 + OH- K = 1.6 x 10-7 What is the conjugate base of H2PO4-? a. HPO42- b. H2O c. OH- d. H3PO4

HPO42-

In the reaction , _____. HPO42- is a conjugate acid HPO42- is a conjugate base NH3 is an acid NH4+ is a conjugate base

HPO42- is a conjugate base

Weak acids include which of the following? I. HF II. HI III. HNO2 a. I only b. II only c. III only d. I and III only

I and III only

According to Bronsted Lowry theory, which of the following anions is the weakest base? a. I- b. NO2- c. CH3COO- d. ClO-

I- Place a hydrogen on each ion to make them acids. HI is the only strong acid. The stronger the acid, the weaker the conjugate base.

The strength of an acid depends on _____. A) properties of the solvent B) temperature C) molecular structure of the acid D) all of the above

all of the above All of these are related to the ability of an acid to lose a hydrogen ion to the solvent

A Brønsted acid is a(n) _____. A) proton donor B) hydroxide ion donor C) proton acceptor D) electron donor

proton donor

Which one of the following statements is true? A) The conjugate base of a strong acid is strong. B) The conjugate base of a strong acid is weak. C) The conjugate acid of a weak base is weak. D) H2SO4 is a strong acid. Therefore, HSO4- is a strong conjugate base.

The conjugate base of a strong acid is weak. The stronger the acid, the weaker the conjugate base

Which of the following statements is true with respect to the reaction below? The reaction favors the formation of F-(aq). F- is a stronger base than OH-. Hydrofluoric acid is a weaker acid than water. The reaction favors the formation of HF(aq).

The reaction favors the formation of F-(aq). Bronsted Lowry acid base equilibria favor formation of weaker acid and weaker base... in this reaction fluoride ion is the base on the left, and hydroxide is the base on the right. Hydroxide is stronger base than fluoride—so equilibrium favors fluoride

The hydrogen ion concentration of a solution having a pH of 2.42 is _____. 3.8 10 -3 M 3.8 10 -2 M 3.8 10 2 M 2.4 10 -3 M

Use [H+] = 10-pH

7. Given the following hypothetical weak acids, which ion below is the strongest conjugate base? HX Ka = 1.0 x 10-6 HQ Ka = 1.0 x 10-4 HZ Ka = 5.0 x 10-4 HR Ka = 5.0 x 10-3 a. X- b. Q- c. Z- d. R-

X-

Which one of the following hydroxides is amphoteric? a. Ca(OH)2 b. Ba(OH)2 c. Fe(OH)2 d. Zn(OH)2

Zn(OH)2

Which of the following is true for a solution having pH < 7? [H+] < 10 -7 M [OH-] > 10 -7 M It is a basic solution. [H+] > 10 -7 M

[H+] > 10 -7 M Solution is acidic therefore more hydronium in solution than hydroxide... at neutral pH of 7 hydrogen ion is 1.0 x 10-7 M for pH to drop below 7, hydrogen ion concentration needs to move greater than 1 x 10-7

Which of the following is correct relating [H+] and [OH-] in solution at 25C? A) [H+] + [OH-] = 1 10-14 B) [H+] + [OH-] = 14.0 C) [H+] [OH-] = 1 1014 D) [H+] [OH-] = 1 10-14

[H+] [OH-] = 1 10-14

Arrange the following in order of increasing acid strength. H2O, H2Te, H2S, H2S a. H2O < H2Te < H2Se < H2S b. H2Se < H2Te < H2O < H2S c. H2Te < H2Se < H2S < H2O d. H2O < H2S < H2Se < H2Te

a. H2O < H2S < H2Se < H2Te

When 0.10 M solutions of HF, HCl, KF and KCl are arranged in order of increasing pH which order is correct? a. HF, HCl, KF, KCl b. HCl, HF, KF, KCl c. HCl, HF, KCl, KF d. HF, HCl, KCl, KF

a. HCl, HF, KCl, KF Strongest acid weaker acid neutral weaker bases stronger bases HCl strong acid, HF weaker acid, KCl salt no hydrolysis KF fluoride ion hydrolyses and makes OH- weaker base

Which is the weakest acid? a. Ascorbic acid (Ka = 8.0 x 10-5) b. Boric acid (Ka = 5.8 x 10-10) c. Butyric acid (Ka = 1.5 x 10-5) d. Hydrocyanic acid (Ka = 4.9 x 10-10)

a. Hydrocyanic acid (Ka = 4.9 x 10-10) Smaller the Ka value the weaker the acid

Which weak acid has the strongest conjugate base? a. Acetic acid Ka = 1.8 x 10-5 b. Formic acid Ka = 1.8 x 10-4 c. Hydrofluoric acid Ka = 6.8 x 10-4 d. Propanoic acid Ka = 5.5 x 10-5

a. Propanoic acid Ka = 5.5 x 10-5

Which solution has the greatest percent ionization? a. 0.010 M formic acid (Ka = 1.8 x 10-4) b. 0.10 M formic acid (Ka = 1.8 x 10-4) c. 0.010 M acetic acid (Ka = 1.8 x 10-5) d. 0.10 M acetic acid (Ka = 1.8 x 10-5)

0.010 M formic acid (Ka = 1.8 x 10-4) Larger the value of Ka or Kb the greater the ionization, and also the more dilute the solution the greater the ionization.

Which one of the following will have the lowest pH? 0.04 M H2SO4 0.04 M CH3COOH 0.04 M HCl 0.04 M NH3

0.04 M H2SO4 Lowest pH means highest hydronium ion concentration which means strongest acid. HCl and H2SO4 are both strong acids. However sulfuric acid is diprotic and the second step has a Ka value around 10-2 so the second step provides some measurable hydronium—hence sulfuric acid will provide more hydronium ion.

Ka CH3COOH 1.8 x 10-5 HCN 5.8 x 10-10 Which solution has the highest pH? a. 0.10 M CH3COOH b. 0.10 M HCN c. 0.10 M CH3COOK d. 0.10 M NaBr

0.10 M CH3COOK Highest pH means lowest amount of hydronium (weakest acid). NaBr is a neutral salt so its pH = 7. Acetic acid strongest acid shown so its pH will be lowest. CH3COOK is a salt in soln CH3COO- + HOH ↔ CH3COOH + OH- therefore this salt makes OH-. HCN is an acid makes hydronium.

What is the pH of a 0.025 M solution of KOH? a. 1.60 b. 3.69 c. 10.31 d. 12.40

12.40

The pH of a 0.62 M KOH solution is _____. A) 0.21 B) 13.79 C) 1.21 D) 12.79

13.79 Take log of 0.62 this will pOH then use 14 = pOH + pH

Formic Acid, Ka HCOOH 1.9 x 10-4 What is the pH of a 0.15 M solution of formic acid, HCOOH? a. 1.49 b. 2.27 c. 3.72 d. 4.55

2.27 Use box structure to find x, then find pH

Ka C6H8O6 8.0 x 10-5 What is the [H+] in a 0.10 M solution of ascorbic acid, C6H8O6? a. 8.0 x 10-6 M b. 2.8 x 10-3 M c. 4.0 x 10-3 M d. 5.3 x 10-3 M

2.8 x 10-3 M

What is the pH of a 0.0015 M solution of HNO3? a. 1.41 b. 2.82 c. 5.65 d. 11.18

2.82

What is the concentration of a solution of K2CO3 that has a pH = 11.90? (For H2CO3 Ka1 = 4.2 x 10-7, Ka2 = 4.8 x 10-11) a. 3.0 x 10-1 M b. 2.6 x 10-2 M c. 7.9 x 10-3 M d. 1.3 x 10-12 M

3.0 x 10-1 M This question is poorly worded, but it implies the equilibrium concentration of CO32-. This is a salt, so hydrolysis occurs. CO32- + HOH ↔ HCO3- + OH- Find Kb for carbonate : Kb= = 2.1 x 10-4 Convert the pH to [OH-] pOH = 14 -11.90 = 2.10 [OH-] = 10-2.10 = 0.0079 M Plug into MAE 2.1 x 10-4 = 0.30 M

In a solution of formic acid (Ka = 1.7 x 10-4) , the [H+] = 2.3 x 10-3. What is the concentration of formic acid in mol·L-1? a. 7.2 x 10-2 b. 3.1 x 10-2 c. 5.3 x 10-6 d. 3.9 x 10-7

3.1 x 10-2 Write reaction for formic acid in water. Set up box structure using IN or y to represent the initial concentration of formic acid. Use pH to find value of x Plug into MAE and solve for either IN or y

10. Acetylsalicylic acid behaves as an acid according to the equation shown. Calculate Kb for the C9H7O4- ion. (Ka = 3.0 x 10-4) HC9H7O4 + H2O ↔ H3O+ + C9H7O4- a. 3.0 x 10-17 b. 3.3 x 10-11 c. 9.0 x 10-8 d. 3.3 x 103

3.3 x 10-11

The ionization constant of hypochlorous acid represented above has a K of 3.0 x 10-8 at 25 C. What is the K for this reaction? OCl- + H2O ↔ HOCl + OH- a. 3.3 x 10-7 b. 3.0 x 10-8 c. 3.0 x 104 d. 3.3 x 107

3.3 x 10-7 This the hydrolysis reaction, use Kw = Ka · Kb = 1.0 x 10-14 solve for Kb

What is the percentage ionization of HCOOH molecules in a 0.10 M solution? (Ka = 1.8 x 10-4) a. 4.2% b. 2.7% c. 1.8% d. 1.3%

4.2%

0.056 g of CH3COOH (Ka = 1.8 10-5) is dissolved in enough water to obtain 50.0 mL of solution. The concentration of H+ in the solution is _____. A) 1.8 10-4 M B) 1.8 10-3 M C) 5.8 10-3 M D) 5.8 10-4 M

5.8 10-4 M Find molarity of acetic acid use box structure plug into MAE and solve for x

What is the [H+] of a 0.075 M solution of the acid HA? a. 6.1 x 10-4 M b. 2.2 x 10-4 M c. 6.0 x 10-5 M d. 4.8 x 10-8 M

6.0 x 10-5 M Weak acid, use box structure, find hydronium and then pH

. A 0.015 M solution of a weak acid has a pH of 3.52. What is the value of the Ka for this acid? a. 2.0 x 10-2 b. 6.2 x 10-6 c. 9.1 x 10-8 d. 1.4 x 10-9

6.2 x 10-6

The ionization of benzoic acid is represented by this equation. C6H5COOH + H2O ↔ C6H5COO- + H3O+ If a 0.045 M solution of benzoic acid has an [H+] = 1.7 x 10-3, what is the Ka of benzoic acid? a. 7.7 x 10-5 b. 6.4 x 10-5 c. 3.8 x 10-2 d. 8.4 x 10-1

6.4 x 10-5 Use box, use hydronium ion concentration as x, solve for concentrations and plug into MAE

The pH of an aqueous solution of KBr will be _____. > 7 < 7 0 7

7

The pH of a 0.30 M solution of a weak base is 10.66. What is the Kb of the base? 4.8 10-10 1.85 10-5 7.0 10-8 7.0 10-7

7.0 10-7 Write the equation for a weak base in water B + HOH ↔ BH+ + OH-, set up box structure, use pH to find hydroxide ion concentration ( pH pOH 10-pOH) this is x plug into box structure find concentrations plug into MAE

At 20 C water has a Kw of 6.807 x 10-15. What is the pH of pure water at this temperature? a. 6.667 b. 6.920 c. 7.000 d. 7.084

7.084

17. A 0.040 M monoprotic acid solution is 14% ionized. Its Ka value is _____. A) 9.1 10-4 B) 4.6 10-3 C) 2.3 10-6 D) 9.2 10-5

A. Use the equation HA + H2O ↔ H3O+ + A- and set up the box structure. Take 14% of 0.040 molar concentration that gives the value of x, plug x in to box structure and turn equilibrium concentrations into molarity values instead of expressions for x then plug into MAE and find Ka.

. A 0.10 molar solution of which salt is most acidic? a. NH4C2H3O2 b. NaCN c. KNO3 d. AlCl3

AlCl3 Aluminum(III) cations act the same way as transition metal cations- producing hydronium ions during hydrolysis. Transition metal cations hydrolyze better than NH compounds.

When 0.10 M solutions of ammonium acetate, NH4C2H3O2, barium acetate, Ba(C2H3O2)2, and sodium acetate, NaC2H3O2, are ranked from least basic to most basic, what is the correct ordering? a. Ammonium acetate < sodium acetate < barium acetate b. Barium acetate < ammonium acetate < sodium acetate c. Sodium acetate < barium acetate < ammonium acetate d. Sodium acetate < ammonium acetate < barium acetate

Ammonium acetate < sodium acetate < barium acetate Least basic (most acidic) to most basic (least acidic) Acetate, C2H3O2- will produce OH- in water as result of hydrolysis Ammonium, NH4+ will produce H3O+ in water Ka ammonium = 5.6 x 10-10 Kb acetate = 5.6 x 10-10 therefore ammonium acetate will be a neutral salt ammonium makes the same amount of hydronium as acetate makes hydroxide. Barium acetate is Ba(C2H3O2)2 which means acetate is 0.20 M therefore barium acetate is more alkaline than sodium acetate.

6. According to Lewis: A) An acid is an electron pair donor. B) An acid is electron pair acceptor. C) A base is electron pair acceptor. D) AlCl3 is a base.

An acid is electron pair acceptor.

19. An example of a diprotic acid is _____. A) benzoic acid B) carbonic acid C) formic acid D) hydrofluoric acid

B) carbonic acid

An example of a Lewis acid is _____. NH3 OH- BCl3 I-

BCl3 BCl3 is electron poor or had a double bond depending how one draws the Lewis Structure

Which one of the following is NOT an amphoteric hydroxide? a. Be(OH)2 b. Cr(OH)3 c. Al(OH)3 d. Zn(OH)2

Be(OH)2

Which one of the following will act only as a Brønsted base? A) H2C2O4 B) HC2O4- C) C2O42- D) H3O+

C2O42-

The reaction above has an equilibrium constant less than 1. What is the strongest base in this system? a. C6H5OH b. CN- c. HCN d. C6H5O-

C6H5O-

Which of the following 0.40 M solutions has the highest pH? HCOOH HCl HNO3 CH3COOH

CH3COOH Remember highest ph means smallest hydrogen ion concentration, since all solutions are 0.40 molar the weakest acid has the smallest Ka

H2CO3 + H2O ↔ HCO3- + H3O+ HCO3- + H2O ↔ CO32- + OH- According to the reactions above, what is the conjugate base of HCO3-? a. H2CO3 b. H2O c. H3O+ d. CO32-

CO32-

Which of the following can ONLY act both as a Brønsted base? A) NH3 B) H2O C) CO32- D) OH-

CO32-

. Even though HClO4 and HIO4 are both strong acids in water, in other solvents HClO4 is stronger than HIO4 because a. Chlorine is a smaller atom than iodine. b. Chlorine is more electronegative than iodine. c. Chlorine is in a higher oxidation state than iodine. d. All of the above.

Chlorine is more electronegative than iodine.

Which one of the following is a weak acid? HCOOH b. HCl c. HBr d. H2SO4

HCOOH

Which of the following is a Lewis base? A) CO2 B) H2O C) SO2 D) AlCl3

H2O Unshared pair of electrons on oxygen, SO2 can act as both it has an unshared pair of electrons and also a double bond

The conjugate acid of HSO4¯ is _____. A) H2SO4 B) SO4 2- C) SO32- D) HSO3-

H2SO4

The correct order of the strength of the acids below is _____. H2SeO4 > H2SO4 H2SO4 > H2SeO4 H3PO4 < H3AsO4 HClO > HClO4

H2SO4 > H2SeO4

Normally Ka values are quoted for an acid such as _____. A) HCl B) HNO3 C) H2SO4 D) HCN

HCN Strong acids do not have Ka since they undergo 100% ionization

The reaction : NH21- + HCO31- ↔ NH3 + CO32- has an equilibrium constant greater than 1. Therefore, the strongest base in the reaction above is? a. NH2- b. HCO3- c. NH3 d. CO32-

NH2- Assign each substance as an acid, a base, a conjugate acid or a conjugate base. Now focus only on the bases. Since K>1, the reaction favors ( products or reactants)? Bronsted Lowry acid base equilibria favor (stronger acids and bases or weaker acids and bases)?

A 0.1 M solution of which salt will have a pH less than 7? a. NaCl b. NH4Br c. KF d. CH3COONa

NH4Br

Which salt gives the most acidic 0.10 M solution in water? a. NaCl b. NaNO2 c. NH4Cl d. NH4NO2

NH4Cl NaCl is neutral, NaNO2 is alkaline, NH4Cl acidic, NH4NO2 is slightly acidic, in this case NO2- hydrolyses to produce hydroxide but not quite as well as NH4+ so there will be some hydronium left, but not as much as would be with NH4Cl

When 0.050 M solutions of NH3, KOH, NH4Cl, and KNO2 are arranged in order of increasing pH which order is correct? (Ka HNO2 = 10-4, Kb NH3= 10-5) a. KOH, NH3, NH4Cl, KNO2 b. NH4Cl, NH3, KNO2, KOH c. KNO2, NH4Cl, NH3, KOH d. NH4Cl, KNO2, NH3, KOH

NH4Cl, KNO2, NH3, KOH NH3 is a weak base, KOH is a strong base, NH4Cl is a salt that undergoes acid hydrolysis, and KNO2 is a salt that undergoes base hydrolysis. KNO2 and NH3 both fall into the category of weak bases, use Kb to evaluate the relative strength of these two weak bases. Since HNO2 has an approximate Ka of 10-4, therefore the Kb for NO2- is approximately 10-10 which is much smaller than 10-5 for ammonia

Which salt will not undergo hydrolysis? A) KF B) Na2CO3 C) K2SO4 D) NaI

NaI

Which salt produces the most alkaline solution at a concentration of 0.1 M ? a. KNO3 b. MgCl2 c. NH4Cl d. NaNO2

NaNO2 KNO3 neutral salt, MgCl2 neutral salt, NH4Cl acidic salt, NaNO2 alkaline salt

Nitrous acid, HNO2, has a Ka of 4.5 x 10-4. What is the best description of the species present in a 0.10 M solution of nitrous acid? a. Nitrous acid is the predominate species; much smaller amounts of hydronium ion and nitrite ion exist. b. Hydronium ion and nitrite ion are the predominate species; much smaller amounts of nitrous acid is present. c. Only hydronium ion and nitrite ion are present in measurable amounts. d. Nitrous acid, hydronium ion and nitrite ion are all present in comparable amounts.

Nitrous acid is the predominate species; much smaller amounts of hydronium ion and nitrite ion exist.

What is conjugate base of HSO4-? a. H+ b. H2SO4 c. OH- d. SO42-

SO42-

The strength of an oxoacid depends on the _____ of the central atom. A) electronegativity B) oxidation state C) electronegativity and oxidation state D) electron affinity.

electronegativity and oxidation state