CHM2046L Final Exam at the University of Florida, complete with a 200-question
practice
CHM2046L Final Exam Practice: 170 Questions with Answers & Rationales
University of Florida | General Chemistry II Laboratory
SECTION 1: SPECTROPHOTOMETRY & BEER-LAMBERT LAW (Questions 1-35)
Question 1
Which of the following is the correct mathematical expression for the Beer-
Lambert law?
A) A = ε d c
B) A = ε / (d c)
C) A = d c / ε
D) A = ε d / c
Answer: A
Rationale: The Beer-Lambert law states that absorbance (A) is directly
proportional to the molar absorptivity (ε), the path length (d) of the cuvette in
,cm, and the concentration (c) of the absorbing species in mol/L. The equation is A
= ε d c. This linear relationship is the foundation of quantitative
spectrophotometric analysis.
Question 2
A solution of a colored compound has an absorbance of 0.451 at a concentration
of 2.0 × 10⁻⁵ M in a 1.00 cm cuvette. What is the molar absorptivity (ε) of the
compound?
A) 1.13 × 10³ L mol⁻¹ cm⁻¹
B) 2.26 × 10⁴ L mol⁻¹ cm⁻¹
C) 4.52 × 10⁴ L mol⁻¹ cm⁻¹
D) 9.04 × 10⁴ L mol⁻¹ cm⁻¹
Answer: B
Rationale: Using the Beer-Lambert law, A = ε d c, rearrange to solve for ε: ε = A /
(d × c). Substituting the values: ε = 0.451 / (1.00 cm × 2.0 × 10⁻⁵ M) = 0.451 / (2.0 ×
10⁻⁵) = 2.255 × 10⁴ L mol⁻¹ cm⁻¹. Molar absorptivity is an intrinsic property of a
compound at a specific wavelength.
,Question 3
You generate a Beer-Lambert calibration curve and obtain the linear regression
equation y = 22066x + 0.003 with an R² value of 0.999. What does the y-intercept
represent in this context?
A) The molar absorptivity of the compound
B) The absorbance of a solution with zero concentration of the colored analyte
C) The concentration of the most dilute standard
D) The path length of the cuvette
Answer: B
Rationale: In a Beer-Lambert calibration curve of absorbance (y) vs. concentration
(x), the y-intercept is the theoretical absorbance at zero concentration. It should
ideally be zero. A non-zero y-intercept indicates systematic error, such as
improper blanking (not zeroing the spectrophotometer correctly), stray light, or a
baseline offset in the instrument.
Question 4
, A student measures the absorbance of an unknown solution and obtains A = 1.25.
Using the calibration curve equation y = 22066x + 0.003, what is the
concentration of the unknown solution?
A) 2.50 × 10⁻⁵ M
B) 5.65 × 10⁻⁵ M
C) 6.77 × 10⁻⁵ M
D) 1.25 × 10⁻⁵ M
Answer: B
Rationale: Substitute y = 1.25 into the calibration equation: 1.25 = 22066x + 0.003.
Subtract 0.003 from both sides: 1.247 = 22066x. Divide both sides by 22066: x =
1. = 5.65 × 10⁻⁵ M. Always check that your unknown absorbance falls
within the linear range of your calibration curve for accurate quantitation.
Question 5
A student fails to zero the spectrophotometer with a blank solution before
measuring standards. How will this affect the calibration curve?
A) The slope will increase
practice
CHM2046L Final Exam Practice: 170 Questions with Answers & Rationales
University of Florida | General Chemistry II Laboratory
SECTION 1: SPECTROPHOTOMETRY & BEER-LAMBERT LAW (Questions 1-35)
Question 1
Which of the following is the correct mathematical expression for the Beer-
Lambert law?
A) A = ε d c
B) A = ε / (d c)
C) A = d c / ε
D) A = ε d / c
Answer: A
Rationale: The Beer-Lambert law states that absorbance (A) is directly
proportional to the molar absorptivity (ε), the path length (d) of the cuvette in
,cm, and the concentration (c) of the absorbing species in mol/L. The equation is A
= ε d c. This linear relationship is the foundation of quantitative
spectrophotometric analysis.
Question 2
A solution of a colored compound has an absorbance of 0.451 at a concentration
of 2.0 × 10⁻⁵ M in a 1.00 cm cuvette. What is the molar absorptivity (ε) of the
compound?
A) 1.13 × 10³ L mol⁻¹ cm⁻¹
B) 2.26 × 10⁴ L mol⁻¹ cm⁻¹
C) 4.52 × 10⁴ L mol⁻¹ cm⁻¹
D) 9.04 × 10⁴ L mol⁻¹ cm⁻¹
Answer: B
Rationale: Using the Beer-Lambert law, A = ε d c, rearrange to solve for ε: ε = A /
(d × c). Substituting the values: ε = 0.451 / (1.00 cm × 2.0 × 10⁻⁵ M) = 0.451 / (2.0 ×
10⁻⁵) = 2.255 × 10⁴ L mol⁻¹ cm⁻¹. Molar absorptivity is an intrinsic property of a
compound at a specific wavelength.
,Question 3
You generate a Beer-Lambert calibration curve and obtain the linear regression
equation y = 22066x + 0.003 with an R² value of 0.999. What does the y-intercept
represent in this context?
A) The molar absorptivity of the compound
B) The absorbance of a solution with zero concentration of the colored analyte
C) The concentration of the most dilute standard
D) The path length of the cuvette
Answer: B
Rationale: In a Beer-Lambert calibration curve of absorbance (y) vs. concentration
(x), the y-intercept is the theoretical absorbance at zero concentration. It should
ideally be zero. A non-zero y-intercept indicates systematic error, such as
improper blanking (not zeroing the spectrophotometer correctly), stray light, or a
baseline offset in the instrument.
Question 4
, A student measures the absorbance of an unknown solution and obtains A = 1.25.
Using the calibration curve equation y = 22066x + 0.003, what is the
concentration of the unknown solution?
A) 2.50 × 10⁻⁵ M
B) 5.65 × 10⁻⁵ M
C) 6.77 × 10⁻⁵ M
D) 1.25 × 10⁻⁵ M
Answer: B
Rationale: Substitute y = 1.25 into the calibration equation: 1.25 = 22066x + 0.003.
Subtract 0.003 from both sides: 1.247 = 22066x. Divide both sides by 22066: x =
1. = 5.65 × 10⁻⁵ M. Always check that your unknown absorbance falls
within the linear range of your calibration curve for accurate quantitation.
Question 5
A student fails to zero the spectrophotometer with a blank solution before
measuring standards. How will this affect the calibration curve?
A) The slope will increase
