CHM2046L Final Exam UF Spring
2025/2026 questions n answers
beer-lambert law - ANS ✔✔A = εdc
A = absorbance
ε = molar absorptivity (L mol-1 cm-1)
d = distance the light travels through the solution (the cuvette) in cm
c = concentration of the solution (mol/L)
Beer's Law calibration curve:
Use the following data to generate a calibration curve of Absorbance vs Concentration at λmax =
420.6 nm.
concentration 1: 6e-5 M; absorbance 1: 1.330
concentration 2: 2e-5 M; absorbance 1: 0.451
concentration 1: 1e-5 M; absorbance 1: 0.239
concentration 1: 2e-6 M; absorbance 1: 0.042
Record the equation and analyze your data:
,- do all of the data points fall on the trendline? Is your R2 value greater than 0.990?
- what does y represent?
- what does x represent?
- why should the y-intercept of the linear trendline be very close to 0? - ANS ✔✔equation:
y=22066x + 0.008
yes, all points fall on the trendline or are very close. R2 = 0.9998
y = absorbance
x = solute concentration (mol/L)
a y-intercept of 0 indicates 0 absorbance at 0 M concentration of colored solute
Serial Dilution:
- Perform calculations to determine the amount of 6.00x10-5 M stock solution needed to
prepare 20.00 mL of 2.00x10-5 M dye solution.
- Perform calculations to determine the amount of 2.00x10-5 M stock solution needed to
prepare 20.00 mL of 1.00x10-5 M dye solution.
- Perform calculations to determine the amount of 1.00x10-5 M stock solution needed to
prepare 20.00 mL of 2.00x10-6 M dye solution. - ANS ✔✔x = 6.67 ml
,x = 10 ml
x = 4 ml
using this Beer's Law calibration curve equation, y=22066x + 0.008, at λmax = 420.6 nm,
determine the concentrations for each of the absorbances values below:
absorbance 1: 2.224
absorbance 2: 1.558
if absorbance 1 is from a 1e-3 M stock solution and absorbance 2 is from a 1e-4 M stock
solution, do all of these data points follow Beer's Law? (did the concentrations you obtained
using the equation match the concentrations of the stock solutions?). If not, why? (***hint: look
at the excel graph you generated and determine the maximum absorbance at λmax = 420.6 nm
that falls on/very close to the trendline) - ANS ✔✔for absorbance 1:
x = 1e-4 M
for absorbance 2:
x = 7.02e-5 M
No. These concentrations obtained from the absorbances, y = 2.224 and y = 1.558, do not follow
Beer's Law. The concentrations calculated do not match the stock solution concentrations, 1e-3
M and 1e-4 M. The maximum absorbance value that follows Beer's Law is 1.330 at λmax = 420.6
nm because 1.330 falls on the trendline. The absorbances, y = 2.224 and y = 1.558, do not
follow the trendline because their absorbances surpass the maximum absorbance at λmax =
420.6 nm.
, consider that you have a 100 mM stock solution and you need to prepare 10 ml of a 30 mM
solution.
How many ml of the stock solution do you need?
How many ml of deionized water do you need?
enter each of your answers to 2 sig figs - ANS ✔✔3.0 ml stock
7.0 ml DI water
visible light wavelengths - ANS ✔✔red: 630-750 nm
orange: 590-630
yellow: 560-590
green: 480-560
blue: 430-480
violet: 400-430
if a solution appears green, approximately what wavelength of light is it absorbing?
a. 400 nm
2025/2026 questions n answers
beer-lambert law - ANS ✔✔A = εdc
A = absorbance
ε = molar absorptivity (L mol-1 cm-1)
d = distance the light travels through the solution (the cuvette) in cm
c = concentration of the solution (mol/L)
Beer's Law calibration curve:
Use the following data to generate a calibration curve of Absorbance vs Concentration at λmax =
420.6 nm.
concentration 1: 6e-5 M; absorbance 1: 1.330
concentration 2: 2e-5 M; absorbance 1: 0.451
concentration 1: 1e-5 M; absorbance 1: 0.239
concentration 1: 2e-6 M; absorbance 1: 0.042
Record the equation and analyze your data:
,- do all of the data points fall on the trendline? Is your R2 value greater than 0.990?
- what does y represent?
- what does x represent?
- why should the y-intercept of the linear trendline be very close to 0? - ANS ✔✔equation:
y=22066x + 0.008
yes, all points fall on the trendline or are very close. R2 = 0.9998
y = absorbance
x = solute concentration (mol/L)
a y-intercept of 0 indicates 0 absorbance at 0 M concentration of colored solute
Serial Dilution:
- Perform calculations to determine the amount of 6.00x10-5 M stock solution needed to
prepare 20.00 mL of 2.00x10-5 M dye solution.
- Perform calculations to determine the amount of 2.00x10-5 M stock solution needed to
prepare 20.00 mL of 1.00x10-5 M dye solution.
- Perform calculations to determine the amount of 1.00x10-5 M stock solution needed to
prepare 20.00 mL of 2.00x10-6 M dye solution. - ANS ✔✔x = 6.67 ml
,x = 10 ml
x = 4 ml
using this Beer's Law calibration curve equation, y=22066x + 0.008, at λmax = 420.6 nm,
determine the concentrations for each of the absorbances values below:
absorbance 1: 2.224
absorbance 2: 1.558
if absorbance 1 is from a 1e-3 M stock solution and absorbance 2 is from a 1e-4 M stock
solution, do all of these data points follow Beer's Law? (did the concentrations you obtained
using the equation match the concentrations of the stock solutions?). If not, why? (***hint: look
at the excel graph you generated and determine the maximum absorbance at λmax = 420.6 nm
that falls on/very close to the trendline) - ANS ✔✔for absorbance 1:
x = 1e-4 M
for absorbance 2:
x = 7.02e-5 M
No. These concentrations obtained from the absorbances, y = 2.224 and y = 1.558, do not follow
Beer's Law. The concentrations calculated do not match the stock solution concentrations, 1e-3
M and 1e-4 M. The maximum absorbance value that follows Beer's Law is 1.330 at λmax = 420.6
nm because 1.330 falls on the trendline. The absorbances, y = 2.224 and y = 1.558, do not
follow the trendline because their absorbances surpass the maximum absorbance at λmax =
420.6 nm.
, consider that you have a 100 mM stock solution and you need to prepare 10 ml of a 30 mM
solution.
How many ml of the stock solution do you need?
How many ml of deionized water do you need?
enter each of your answers to 2 sig figs - ANS ✔✔3.0 ml stock
7.0 ml DI water
visible light wavelengths - ANS ✔✔red: 630-750 nm
orange: 590-630
yellow: 560-590
green: 480-560
blue: 430-480
violet: 400-430
if a solution appears green, approximately what wavelength of light is it absorbing?
a. 400 nm
