CHM2046L FINAL EXAM UF SPRING
2021
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
b.-470-nm
c.-520-nm
d.-580-nm
e.-630-nm
f.-700-nm
(image-of-wavelengths-provided-when-u-flip-this-card)---ans-✔✔f.-700-nm
if-the-solution-is-green,-then-it-is-absorbing-red-light-(opposite-color-on-the-color-wheel)
for-a-red-dye,-a-calibration-curve-for-absorbance-versys-concentration-was-plotted-and-it-
yielded-a-trendline-with-an-equation-of-y=-31,870x-+-0.0012.-If-an-unknown-sample-of-red-
dye-has-an-absorbance-of-0.807,-what-is-the-concentration-of-the-sample?
enter-your-answer-in-units-of-micromolar-(μM)---ans-✔✔25.3
the-concentration-of-dye-in-Solution-A-is-23.8-M.-A-serial-dilution-is-performed-to-make-
Solutions-B-and-C.-
In-the-1st-dilution,-7-ml-of-Solution-A-is-diluted-with-12-ml-of-water-to-make-Solution-B.-
then,-2-ml-of-Solution-B-is-then-diluted-with-1-ml-of-water-to-make-Solution-C.-
2021
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
b.-470-nm
c.-520-nm
d.-580-nm
e.-630-nm
f.-700-nm
(image-of-wavelengths-provided-when-u-flip-this-card)---ans-✔✔f.-700-nm
if-the-solution-is-green,-then-it-is-absorbing-red-light-(opposite-color-on-the-color-wheel)
for-a-red-dye,-a-calibration-curve-for-absorbance-versys-concentration-was-plotted-and-it-
yielded-a-trendline-with-an-equation-of-y=-31,870x-+-0.0012.-If-an-unknown-sample-of-red-
dye-has-an-absorbance-of-0.807,-what-is-the-concentration-of-the-sample?
enter-your-answer-in-units-of-micromolar-(μM)---ans-✔✔25.3
the-concentration-of-dye-in-Solution-A-is-23.8-M.-A-serial-dilution-is-performed-to-make-
Solutions-B-and-C.-
In-the-1st-dilution,-7-ml-of-Solution-A-is-diluted-with-12-ml-of-water-to-make-Solution-B.-
then,-2-ml-of-Solution-B-is-then-diluted-with-1-ml-of-water-to-make-Solution-C.-
