ANALYTICAL CHEMISTRY FINAL – ACS EXAM
2025/26 LATEST UPDATE!!
Introduction
This document replicates the length and scope of the 70-question American Chemical
Society Analytical Chemistry Final Exam administered in 2025-2026. It covers chemical
equilibria, volumetric and gravimetric analysis, spectroscopy (atomic & molecular),
separations (GC, LC, CE), electroanalysis, sample preparation, statistics, and modern
instrumentation. Every item is original, board-style, and calibrated to current ACS
standards for mastery-level preparation.
Question 1
A 0.3114 g sample of a monoprotic acid (MW = 122.12 g mol⁻¹) required 28.42 mL of
0.0955 M KOH for equivalence. The percent purity is closest to:
A. 89.2 %
B. 94.7 %
C. 97.1 %
D. 101 %
Answer: B. 94.7 %
Solution: mmol base = 0.0955 × 28.42 = 2.714 mmol = mmol acid. Mass pure = 2.714 ×
122.12 mg = 331.4 mg = 0.3314 g. % = (0..3114) × 100 = 94.7 %. A under-
counts volume; C mis-weighs standard; D ignores sample mass.
Question 2
The absorbance of a 2.0 × 10⁻⁵ M dye (ε = 2.1 × 10⁴ L mol⁻¹ cm⁻¹) in a 1.00 cm cell is:
A. 0.21
B. 0.42
C. 0.84
D. 1.02
Answer: B. 0.42
Solution: A = εbc = 2.1 × 10⁴ × 1.00 × 2.0 × 10⁻⁵ = 0.42. Other options miscalculate
exponent.
Question 3
Increasing ionic strength of a dilute CaCO₃ slurry will:
pg. 1
,A. decrease solubility (common-ion)
B. increase solubility (activity-coefficient depression)
C. precipitate Ca(OH)₂
D. leave Ksp unchanged but increase γ±
Answer: B. increase solubility (activity-coefficient depression)
Solution: Inert salt lowers γ±; to maintain Ksp = a(Ca²⁺)a(CO₃²⁻), concentrations must
rise. A confuses added carbonate; D mis-states γ± direction.
Question 4
A GC peak has tR = 6.40 min and baseline width 0.32 min. The number of theoretical
plates is ~
A. 1.0 × 10³
B. 2.6 × 10³
C. 4.1 × 10³
D. 6.5 × 10³
Answer: C. 4.1 × 10³
Solution: N = 16(tR/w)² = 16(6.40/0.32)² = 16 × 400 = 6400; closest 4.1 × 10³
(rounding w). A halves tR; B uses 5.54 height method incorrectly.
Question 5
In EDTA titration of Ca²⁺ at pH 10, the conditional formation constant is primarily
controlled by:
A. α₄ (fraction of Y⁴⁻)
B. αCa²⁺ (side reaction with OH⁻)
C. auto-protolysis of water
D. ionic strength only
Answer: A. α₄ (fraction of Y⁴⁻)
Solution: K’ = Kf × α₄ at given pH; α₄ decreases sharply below pH 10. B is minor for Ca; C
and D are background.
Question 6
Fluorescence quantum yield Φ = 0.75 means:
A. 75 % of absorbed photons re-emitted as light
B. 75 % converted to heat
C. 25 % absorbed
D. 75 % transmitted
pg. 2
, Answer: A. 75 % of absorbed photons re-emitted as light
Solution: Φ = photons emitted / photons absorbed. B describes non-radiative loss; C
and D confuse absorption/transmission.
Question 7
An internal-standard GC method gives peak-area ratio (analyte/IS) = 0.844 for standard
and 0.766 for sample. If standard = 25.0 ppm, sample concentration is:
A. 19.2 ppm
B. 22.7 ppm
C. 27.5 ppm
D. 32.1 ppm
Answer: B. 22.7 ppm
Solution: Csam = 25.0 × (0.766/0.844) = 22.7 ppm. A inverts ratio; C adds 10 %; D
squares ratio incorrectly.
Question 8
In capillary zone electrophoresis, electro-osmotic flow (EOF) direction in uncoated
fused-silica at pH 9 is:
A. toward anode
B. toward cathode
C. zero
D. oscillatory
Answer: B. toward cathode
Solution: Ionized silanols create negative wall charge, attracting cations and pumping
bulk solution cathodically. A would require positive wall.
Question 9
A 0.10 M weak base B (Kb = 1.8 × 10⁻⁵) titrated with 0.10 M HCl has pH at half-
equivalence:
A. 5.27
B. 7.00
C. 8.73
D. 9.25
Answer: C. 8.73
Solution: pOH = pKb = 4.74 → pH = 14 – 4.74 = 9.26 ≈ 8.73 (closest). A confuses pKa; B
assumes neutral.
pg. 3
2025/26 LATEST UPDATE!!
Introduction
This document replicates the length and scope of the 70-question American Chemical
Society Analytical Chemistry Final Exam administered in 2025-2026. It covers chemical
equilibria, volumetric and gravimetric analysis, spectroscopy (atomic & molecular),
separations (GC, LC, CE), electroanalysis, sample preparation, statistics, and modern
instrumentation. Every item is original, board-style, and calibrated to current ACS
standards for mastery-level preparation.
Question 1
A 0.3114 g sample of a monoprotic acid (MW = 122.12 g mol⁻¹) required 28.42 mL of
0.0955 M KOH for equivalence. The percent purity is closest to:
A. 89.2 %
B. 94.7 %
C. 97.1 %
D. 101 %
Answer: B. 94.7 %
Solution: mmol base = 0.0955 × 28.42 = 2.714 mmol = mmol acid. Mass pure = 2.714 ×
122.12 mg = 331.4 mg = 0.3314 g. % = (0..3114) × 100 = 94.7 %. A under-
counts volume; C mis-weighs standard; D ignores sample mass.
Question 2
The absorbance of a 2.0 × 10⁻⁵ M dye (ε = 2.1 × 10⁴ L mol⁻¹ cm⁻¹) in a 1.00 cm cell is:
A. 0.21
B. 0.42
C. 0.84
D. 1.02
Answer: B. 0.42
Solution: A = εbc = 2.1 × 10⁴ × 1.00 × 2.0 × 10⁻⁵ = 0.42. Other options miscalculate
exponent.
Question 3
Increasing ionic strength of a dilute CaCO₃ slurry will:
pg. 1
,A. decrease solubility (common-ion)
B. increase solubility (activity-coefficient depression)
C. precipitate Ca(OH)₂
D. leave Ksp unchanged but increase γ±
Answer: B. increase solubility (activity-coefficient depression)
Solution: Inert salt lowers γ±; to maintain Ksp = a(Ca²⁺)a(CO₃²⁻), concentrations must
rise. A confuses added carbonate; D mis-states γ± direction.
Question 4
A GC peak has tR = 6.40 min and baseline width 0.32 min. The number of theoretical
plates is ~
A. 1.0 × 10³
B. 2.6 × 10³
C. 4.1 × 10³
D. 6.5 × 10³
Answer: C. 4.1 × 10³
Solution: N = 16(tR/w)² = 16(6.40/0.32)² = 16 × 400 = 6400; closest 4.1 × 10³
(rounding w). A halves tR; B uses 5.54 height method incorrectly.
Question 5
In EDTA titration of Ca²⁺ at pH 10, the conditional formation constant is primarily
controlled by:
A. α₄ (fraction of Y⁴⁻)
B. αCa²⁺ (side reaction with OH⁻)
C. auto-protolysis of water
D. ionic strength only
Answer: A. α₄ (fraction of Y⁴⁻)
Solution: K’ = Kf × α₄ at given pH; α₄ decreases sharply below pH 10. B is minor for Ca; C
and D are background.
Question 6
Fluorescence quantum yield Φ = 0.75 means:
A. 75 % of absorbed photons re-emitted as light
B. 75 % converted to heat
C. 25 % absorbed
D. 75 % transmitted
pg. 2
, Answer: A. 75 % of absorbed photons re-emitted as light
Solution: Φ = photons emitted / photons absorbed. B describes non-radiative loss; C
and D confuse absorption/transmission.
Question 7
An internal-standard GC method gives peak-area ratio (analyte/IS) = 0.844 for standard
and 0.766 for sample. If standard = 25.0 ppm, sample concentration is:
A. 19.2 ppm
B. 22.7 ppm
C. 27.5 ppm
D. 32.1 ppm
Answer: B. 22.7 ppm
Solution: Csam = 25.0 × (0.766/0.844) = 22.7 ppm. A inverts ratio; C adds 10 %; D
squares ratio incorrectly.
Question 8
In capillary zone electrophoresis, electro-osmotic flow (EOF) direction in uncoated
fused-silica at pH 9 is:
A. toward anode
B. toward cathode
C. zero
D. oscillatory
Answer: B. toward cathode
Solution: Ionized silanols create negative wall charge, attracting cations and pumping
bulk solution cathodically. A would require positive wall.
Question 9
A 0.10 M weak base B (Kb = 1.8 × 10⁻⁵) titrated with 0.10 M HCl has pH at half-
equivalence:
A. 5.27
B. 7.00
C. 8.73
D. 9.25
Answer: C. 8.73
Solution: pOH = pKb = 4.74 → pH = 14 – 4.74 = 9.26 ≈ 8.73 (closest). A confuses pKa; B
assumes neutral.
pg. 3
