1032_2nd Exam_1040422 (A)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)Give the equation for a saturated solution in comparing Q with Ksp.
A)Q > Ksp B) Q Ksp C)Q < Ksp D)Q = Ksp
E) none of the above Answer: D
2) Determine the pH of a solution that is 0.15 M HClO2 (Ka = 1.1 x 10-2) and 0.15 M HClO (Ka = 2.9 × 10-8).
A) 4.18 B) 3.55 C) 9.82 D) 1.39 E) 12.55
Answer: D
3)Calculate the pH of a buffer that is 0.225 M HC2H3O2 and 0.162 M KC2H3O2. The Ka for HC2H3O2 is 1.8 × 10-5.
A) 4.74 B) 9.11 C) 9.26 D) 4.60 E) 4.89
Answer: D
4) Determine the molar solubility for Al(OH)3 in pure water. Ksp for Al(OH)3 = 1.3 x 10-33.
A) 3.6 x 10-12 M B) 2.2 x 10-10 M C) 6.0 x 10-19 M D) 4.8 x 10-35 M E) 2.6 x 10-9 M Answer: E
5) Consider the given acid ionization constants. Identify the strongest conjugate base.
Acid K a
HNO2(aq) 4.6 × 10-4 HCHO2(aq) 1.8 × 10-4 HClO(aq) 2.9 × 10-8 HCN(aq) 4.9 × 10-10
A) NO2 (aq) B) CN (aq) C) ClO (aq) D) CHO2 (aq)
Answer: B
6) Consider a buffer composed of the weak acid HA and its conjugate base A . Which pair of concentrations results in the most effective buffer?
A) 0.10 M HA; 0.90 M A B) 0.10 M HA; 0.10 M A
C) 0.90 M HA; 0.10 M A D) 0.50 M HA; 0.50 M A
Answer: D
7) Determine the [OH-] concentration of a 0.741 M KOH solution at 25°C.
A) 0.741 M B) 7.41 M
C) 1.34 x 10-14 M D) 1.34 x 10-13 M
E) none of the above Answer: A
8) A weak unknown monoprotic acid is titrated with a strong base. The titration curve is shown below. Find Ka for the unknown acid.
A) 3.2 × 10-7 B) 3.2 × 10-5 C) 2.5 × 10-9 D) 2.5 × 10-3
Answer: B
9)If the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.11, which of the following is TRUE?
A)[HCHO2] << [NaCHO2]
B)[HCHO2] = [NaCHO2]
C)[HCHO2] > [NaCHO2]
D)[HCHO2] < [NaCHO2]
E)It is not possible to make a buffer of this pH from HCHO2 and NaCHO2.
Answer: C
10)A buffer with a pH of 9.85 contains CH3NH2 and CH3NH3Cl in water. What can you conclude about the relative concentrations of CH3NH2 and CH3NH3Cl in this buffer ? For CH3NH2 , pKb = 3.36.
A)CH3NH2 < CH3NH3Cl B)CH3NH2 > CH3NH3Cl C)CH3NH2 = CH3NH3Cl
D)Nothing can be concluded about the relative concentrations of CH3NH2 and CH3NH3Cl.
Answer: A
11) Determine the concentration of CO32- ions in a 0.18 M H2CO3 solution. Carbonic acid is a diprotic acid whose Ka1 = 4.3 × 10-7 and Ka2 = 5.6 × 10-11.
A) 6.9 × 10-8 M B) 4.3 × 10-7 M C) 3.2 × 10-6 M D) 2.8 × 10-4 M E) 5.6 × 10-11 M Answer: E
12) Determine the pH of a 0.461 M C6H5CO2H M solution if the Ka of C6H5CO2H is 6.5 x 10-5.
A) 4.52 B) 11.74 C) 5.48 D) 2.26 E) 9.48
Answer: D
13)A 100.0 mL sample of 0.18 M HClO4 is titrated with 0.27 M LiOH. Determine the pH of the solution after the addition of 66.67 mL of LiOH (this is the equivalence point).
A) 2.76 B) 0.97 C) 7.00 D) 13.03 E) 11.24
Answer: C
14)A 20.0 mL sample of 0.150 M ethylamine is titrated with 0.0981 M HCl. What is the pH after the addition of 5.0 mL of HCl? For ethylamine, pKb = 3.25.
A) 2.96 B) 11.04 C) 11.46 D) 10.75
Answer: C
15) Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 M NH4Cl with 200.0 mL of 0.12 M NH3. The Kb for NH3 is 1.8 × 10-5.
A) 9.26 B) 4.74 C) 9.06 D) 9.45 E) 4.55
Answer: C
16) Which of the following acids will have the strongest conjugate base?
A) HI B)HClO4 C) HCl D)HNO3 E) HCN
Answer: E
17) A solution containing CaCl2 is mixed with a solution of Li2C2O4 to form a solution that is 3.5 × 10-4 M in calcium ion and 2.33 × 10-4 M in oxalate ion. What will happen once these solutions are mixed? Ksp (CaC2O4)
= 2.3 × 10-9.
A)Nothing will happen Ksp > Q for all possible precipitants.
B) Nothing will happen since both calcium chloride and lithium oxalate are soluble compounds.
C)A precipitate will form since Q > Ksp for calcium oxalate.
D) A precipitate will form as calcium oxalate is not soluble to any extent.
E) There is not enough information to determine.
Answer: C
18)A 100.0 mL sample of 0.20 M HF is titrated with 0.10 M KOH. Determine the pH of the solution before the addition of any KOH. The Ka of HF is 3.5 x 10-4.
19) A 100.0 mL sample of 0.10 M NH3 is titrated with 0.10 M HNO3. Determine the pH of the solution after the addition of 100.0 mL of HNO3. The Kb of NH3 is 1.8 × 10-5.
A) 3.44 B) 5.28 C) 8.72 D) 10.56 E) 6.58
Answer: B
20) Determine the pH in a 0.235 M NaOH solution.
A) 0.24 B) 0.63 C) 13.76 D) 12 E) 13.37
Answer: E
21) Which combination is the best choice to prepare a buffer with a pH of 9.0?
A)C5H5N ; C5H5NHCl (pKb for C5H5N is 8.76) B)HCHO2 ; NaCHO2 (pKa for HCHO2 is 3.74) C)HNO2 ; NaNO2 (pKa for HNO2 is 3.33) D)NH3 ; NH4Cl (pKb for NH3 is 4.75)
Answer: D
22)Calculate the pH of a solution formed by mixing 200.0 mL of 0.30 M HClO with 100.0 mL of 0.20 M KClO. The Ka for HClO is 2.9 × 10-8.
A) 6.46 B) 5.99 C) 7.54 D) 8.01 E) 7.06
Answer: E
23) Determine the pH of a 0.62 M NH4NO3 solution at 25°C. The Kb for NH3 is 1.76 × 10-5.
A) 9.27 B) 4.73 C) 11.52 D) 9.45 E) 2.48
Answer: B
24)A 10.0 mL sample of 0.200 M hydrocyanic acid (HCN) is titrated with 0.0998 M NaOH. What is the pH at the equivalence point? For hydrocyanic acid, pKa = 9.31.
A) 7.00 B) 9.31 C) 8.76 D) 11.07
Answer: D
25) Determine the [H3O ] in a 0.265 M HClO solution. The Ka of HClO is 2.9 × 10-8.
A) 1.1 × 10-10 M B) 4.9 × 10-4 M C) 1.3 × 10-6 M D) 7.7 × 10-9 M E) 8.8 × 10-5 M Answer: E
26) A 500.0 mL buffer solution is 0.10 M in benzoic acid and 0.10 M in sodium benzoate and has an initial pH of 4.19. What is the pH of the buffer upon addition of 0.010 mol of NaOH?
A) 4.29 B) 1.70 C) 4.37 D) 4.01
Answer: C
27) Find the percent ionization of a 0.337 M HF solution. The Ka for HF is 3.5 × 10-4.
A) 1.2 × 10-2 % B) 3.5 × 10-2 % C) 1.1 % D) 4.7 % E) 3.2 %
Answer: E
28) A solution contains 2.2 × 10-3 M in Cu2+ and 0.33 M in LiCN. If the Kf for Cu(CN)42- is 1.0 × 1025, how much copper ion remains at equilibrium?
A) 3.8 × 10-24 M B) 4.6 × 10-25 M C) 2.9 × 10-27 M D) 1.9 x 10-26 M E) 6.7 × 10-28 M Answer: D
29)A 100.0 mL sample of 0.18 M HClO4 is titrated with 0.27 M LiOH. Determine the pH of the solution after the addition of 30.0 mL of LiOH.
A) 1.12 B) 2.86 C) 2.00 D) 0.86 E) 1.21
Answer: A
30) Which pair is a Br nsted–Lowry conjugate acid–base pair?
A) H3O ; OH B) HCl ; HBr C) ClO4 ; ClO3 D) NH3 ; NH4
Answer: D
31) A 1.50 L buffer solution is 0.250 M in HF and 0.250 M in NaF. Calculate the pH of the solution after the addition of 0.100 moles of solid NaOH. Assume no volume change upon the addition of base. The Ka for HF is 3.5 × 10-4.
A) 3.82 B) 3.22 C) 3.69 D) 3.09 E) 4.46
Answer: C
32) A 100.0 mL sample of 0.10 M NH3 is titrated with 0.10 M HNO3. Determine the pH of the solution after the addition of 200.0 mL of HNO3. The Kb of NH3 is 1.8 × 10-5.
A) 12.00 B) 12.52 C) 2.00 D) 1.48 E) 6.44
Answer: D
33) Determine the pH of a 0.188 M NH3 solution at 25°C. The Kb of NH3 is 1.76 × 10-5.
A) 12.656 B) 5.480 C) 11.260 D) 8.520 E) 2.740
Answer: C
34) Which of the following is NOT a conjugate acid-base pair?
A)H3O /OH
B)C2H3O2 /HC2H3O2 C) NH4+/NH3
D)H2SO3/HSO3
E) All of the above are conjugate acid-base pairs.
Answer: A
35) Which of the following solutions would have the highest pH? Assume that they are all 0.10 M in acid at 25 C.
The acid is followed by its Ka value.
A) HF, 3.5 × 10-4 B) HCN, 4.9 × 10-10 C) HCHO2, 1.8 × 10-4 D) HClO2, 1.1 × 10-2
E) HNO2, 4.6 × 10-4 Answer: B
36)A 1.00 L buffer solution is 0.250 M in HF and 0.250 M in NaF. Calculate the pH of the solution after the addition of 100.0 mL of 1.00 M HCl. The Ka for HF is 3.5 × 10-4.
A) 3.82 B) 2.78 C) 4.11 D) 3.46 E) 3.09
Answer: E
37)Place the following in order of increasing acid strength.
HBrO2 HBrO3 HBrO HBrO4
A)HBrO2 < HBrO4 < HBrO < HBrO3 B)HBrO < HBrO2 < HBrO3 < HBrO4 C) HBrO < HBrO4 < HBrO3 < HBrO2 D)HBrO2 < HBrO3 < HBrO4 < HBrO
E)HBrO4 < HBrO2 < HBrO3 < HBrO Answer: B
38)Which of the following bases is the STRONGEST? The base is followed by its Kb.
A) CH3NH2, 4.4 × 10-4 B) C5H5N, 1.7 × 10-9 C) C6H5NH2, 4.0 × 10-10 D) (CH3CH2)2NH, 8.6 × 10-4
E) NH3, 1.76 × 10-5 Answer: D
39)In a triprotic acid, which Ka has the highest value?
A)Ka3 B)Ka1 C)Ka2 D)Kb2 E)Kb1
Answer: B
40)Which acid has the largest Ka : HClO2(aq), HBrO2(aq), or HIO2(aq)?
A)HIO2(aq) B)HClO2(aq)
C)All three acids have the same Ka . D)HBrO2(aq) Answer: B
