CHM 1046 – Complete Question & Answer
Bank (2025/2026)
1. How would you prepare cyclohexylformate or
cyclohexylbutycate? - ANSWER ✔ Cyclohexylformate
can be formed by treating carbon monoxide with an
alcohol, such as methanol, with a catalyst present and it
will form as an ester. Cyclohexylbutycate can be formed
the same way using a different base, alcohol, and catalyst.
2. If your experimental yield of aspirin is greater than
100% how could this occur? If your experimental yield of
aspirin is less than 100% does it necessarily mean your
sample is pure? What are some possible errors in this
case? - ANSWER ✔ A yield greater than 100% could
mean your sample is not dry or your purification didn't
work so you have other reactants/products being weighed.
With less than 100% yield it could still be purse due to
errors. Some possible errors could be spills, incomplete
reaction, side reaction, etc...
, 3. What are the scientifically correct names for A, b, c,
and epsilon in the Beer's law relationship? - ANSWER ✔
A = absorbance, b = cell length/path length, c =
concentration (assume to be 1 if not specifically stated),
epsilon = molar absorptivity
4. What are the units for all of the variables in Beer's
law? - ANSWER ✔ A = unitless, b = cm, c = mol/L,
epsilon = L /(mol x cm)
5. Practice problem: If the absorbance of a solution in a
5cm cell is 3.0, what would be the absorbance of a
solution of the same solute if the cell path length is
reduced to 0.5cm and the concentration is tripled? -
ANSWER ✔ - Part A: 3 = epsilon x 5 x 1
3 = epsilon x 5
3/5 = epsilon = 0.6
- Part B: A = 0.6 x 0.5 x 3 = 0.9
,- Final answer = 0.9
- Explanation: Beer's law formula is A = e x b x c. The
problem states absorbance (A) for one solution is 3 and
the cell length is 5cm (b). Since concentration isn't
mentioned, it can be assumed to be 1. This gives the
formula for part A of 3 = e x 5 x 1 which, when solved
gives us e = 0.6
For part B it states it's a solution of the same solute so
you're using e = 0.6 from part A, but it mentions the cell
path length (b) is reduced to 0.5 and the concentration (c)
is tripled. This gives a new formula of A = 0.6 x 0.5 x 3
which = 0.9 (no units because A, absorbance is unitless.)
6. Beer's law formula - ANSWER ✔ A= epsilon x b x c
7. Although aspirin solutions do not absorb visible light,
we are still able to use visible light in this experiment to
analyze for the purity of aspirin. Why? - ANSWER ✔
, Because when you add iron to aspirin it produces a visible
light reaction that makes it violet
8. If you observe that the color of a solution is a dark red,
what would you estimate the wavelength of the absorbed
radiation to be? - ANSWER ✔ ~700nm
9. To what wavelength setting would you set the
spectrometer in order to give the most sensitive and
accurate Beer's law analyses for determining the aspirin
content in your solutions? - ANSWER ✔ ~400nm
(because that's the wavelength for violet)
10. If a student measured the absorbance of a standard
solution in a 1.00cm cell and then unknowingly used a
1.08cm cell for measurement of the unknown's
absorbance, how would this affect the calculated
concentration of aspirin in the unknown (increase,
decrease, or no effect)? Explain. - ANSWER ✔ It would
increase it because it would increase path length and
absorbance too so to calculate concentration you'd get a
higher number
Bank (2025/2026)
1. How would you prepare cyclohexylformate or
cyclohexylbutycate? - ANSWER ✔ Cyclohexylformate
can be formed by treating carbon monoxide with an
alcohol, such as methanol, with a catalyst present and it
will form as an ester. Cyclohexylbutycate can be formed
the same way using a different base, alcohol, and catalyst.
2. If your experimental yield of aspirin is greater than
100% how could this occur? If your experimental yield of
aspirin is less than 100% does it necessarily mean your
sample is pure? What are some possible errors in this
case? - ANSWER ✔ A yield greater than 100% could
mean your sample is not dry or your purification didn't
work so you have other reactants/products being weighed.
With less than 100% yield it could still be purse due to
errors. Some possible errors could be spills, incomplete
reaction, side reaction, etc...
, 3. What are the scientifically correct names for A, b, c,
and epsilon in the Beer's law relationship? - ANSWER ✔
A = absorbance, b = cell length/path length, c =
concentration (assume to be 1 if not specifically stated),
epsilon = molar absorptivity
4. What are the units for all of the variables in Beer's
law? - ANSWER ✔ A = unitless, b = cm, c = mol/L,
epsilon = L /(mol x cm)
5. Practice problem: If the absorbance of a solution in a
5cm cell is 3.0, what would be the absorbance of a
solution of the same solute if the cell path length is
reduced to 0.5cm and the concentration is tripled? -
ANSWER ✔ - Part A: 3 = epsilon x 5 x 1
3 = epsilon x 5
3/5 = epsilon = 0.6
- Part B: A = 0.6 x 0.5 x 3 = 0.9
,- Final answer = 0.9
- Explanation: Beer's law formula is A = e x b x c. The
problem states absorbance (A) for one solution is 3 and
the cell length is 5cm (b). Since concentration isn't
mentioned, it can be assumed to be 1. This gives the
formula for part A of 3 = e x 5 x 1 which, when solved
gives us e = 0.6
For part B it states it's a solution of the same solute so
you're using e = 0.6 from part A, but it mentions the cell
path length (b) is reduced to 0.5 and the concentration (c)
is tripled. This gives a new formula of A = 0.6 x 0.5 x 3
which = 0.9 (no units because A, absorbance is unitless.)
6. Beer's law formula - ANSWER ✔ A= epsilon x b x c
7. Although aspirin solutions do not absorb visible light,
we are still able to use visible light in this experiment to
analyze for the purity of aspirin. Why? - ANSWER ✔
, Because when you add iron to aspirin it produces a visible
light reaction that makes it violet
8. If you observe that the color of a solution is a dark red,
what would you estimate the wavelength of the absorbed
radiation to be? - ANSWER ✔ ~700nm
9. To what wavelength setting would you set the
spectrometer in order to give the most sensitive and
accurate Beer's law analyses for determining the aspirin
content in your solutions? - ANSWER ✔ ~400nm
(because that's the wavelength for violet)
10. If a student measured the absorbance of a standard
solution in a 1.00cm cell and then unknowingly used a
1.08cm cell for measurement of the unknown's
absorbance, how would this affect the calculated
concentration of aspirin in the unknown (increase,
decrease, or no effect)? Explain. - ANSWER ✔ It would
increase it because it would increase path length and
absorbance too so to calculate concentration you'd get a
higher number
