Chem 1LD Green Questions Review Pack Questions With
Complete Solutions
According to section 2.2 of the SDS sheets, what should you do
if you or a labmate inhales the fumes from heptane or acetone?
Correct Answers If my labmate were to inhale the fumes from
heptane or acetone, I would immediately notify a TA and take
my labmate outside to get some fresh air. Then I would loosen
their clothing and put them into a comfortable position, if
necessary. If they do not feel well, I would get medical
assistance.
Always pre-rinse a cuvette with small amounts of the solution
that it will contain. Why? Correct Answers It is important to
pre-rinse a cuvette with small amounts of the solution that it will
contain because this will remove any leftover residue from
lingering compounds and replace them with the solution of
interest.
Describe the polarity of this solution. Why is this mixture a
more effective mobile phase compared to pure ethyl acetate or
pure ethanol? Correct Answers The ethyl acetate is nonpolar
while the ethanol is polar. If we used pure ethyl acetate, the
solution would be so nonpolar that it would not dissolve the
analyte. If we used pure ethanol, there would not be enough of a
polarity difference between the ethanol and the TLC plate and
the analyte won't travel as far.
Do not recalibrate the spectrometer in between the three
absorption spectra collected above. Why? Correct Answers We
do not recalibrate the spectrometer in between the three
, absorption spectra collected above because we are using the
same solution in all three.
Explain the correct choice of wavelength. Correct Answers 405
nm was chosen instead of 500 nm since our max wavelengths
are closer to 405 nm than 500 nm.
How do impurities affect the melting point of a substance?
(recall melting point depression from Chem 1B) Correct
Answers Impurities in a substance result in a lower melting
point.
How would the clean up process differ if sodium bicarbonate
was added to the purple solution from Part E? Correct Answers
If we were to add sodium bicarbonate to the purple solution
from Part E, the solution would become a brown sludge-like
color. The color would not become transparent like the other
clean up process. This waste would have to go into a different
waste container for special disposal.
If an emulsion does form, brine solution will help. How?
Correct Answers Brine solution adds ions to the aqueous layer,
allowing the more aqueous layer to become more polar. This
will help reduce the emulsion.
If the pressure does not increase after inserting air or ethanol
into the sealed flask using the syringe, what does this signify
about your set-up? Describe three places there could potentially
be leakage in this specific system. Correct Answers If the
pressure does not increase after inserting air or ethanol into the
sealed flask using a syringe, it is possible that there is a leak in
Complete Solutions
According to section 2.2 of the SDS sheets, what should you do
if you or a labmate inhales the fumes from heptane or acetone?
Correct Answers If my labmate were to inhale the fumes from
heptane or acetone, I would immediately notify a TA and take
my labmate outside to get some fresh air. Then I would loosen
their clothing and put them into a comfortable position, if
necessary. If they do not feel well, I would get medical
assistance.
Always pre-rinse a cuvette with small amounts of the solution
that it will contain. Why? Correct Answers It is important to
pre-rinse a cuvette with small amounts of the solution that it will
contain because this will remove any leftover residue from
lingering compounds and replace them with the solution of
interest.
Describe the polarity of this solution. Why is this mixture a
more effective mobile phase compared to pure ethyl acetate or
pure ethanol? Correct Answers The ethyl acetate is nonpolar
while the ethanol is polar. If we used pure ethyl acetate, the
solution would be so nonpolar that it would not dissolve the
analyte. If we used pure ethanol, there would not be enough of a
polarity difference between the ethanol and the TLC plate and
the analyte won't travel as far.
Do not recalibrate the spectrometer in between the three
absorption spectra collected above. Why? Correct Answers We
do not recalibrate the spectrometer in between the three
, absorption spectra collected above because we are using the
same solution in all three.
Explain the correct choice of wavelength. Correct Answers 405
nm was chosen instead of 500 nm since our max wavelengths
are closer to 405 nm than 500 nm.
How do impurities affect the melting point of a substance?
(recall melting point depression from Chem 1B) Correct
Answers Impurities in a substance result in a lower melting
point.
How would the clean up process differ if sodium bicarbonate
was added to the purple solution from Part E? Correct Answers
If we were to add sodium bicarbonate to the purple solution
from Part E, the solution would become a brown sludge-like
color. The color would not become transparent like the other
clean up process. This waste would have to go into a different
waste container for special disposal.
If an emulsion does form, brine solution will help. How?
Correct Answers Brine solution adds ions to the aqueous layer,
allowing the more aqueous layer to become more polar. This
will help reduce the emulsion.
If the pressure does not increase after inserting air or ethanol
into the sealed flask using the syringe, what does this signify
about your set-up? Describe three places there could potentially
be leakage in this specific system. Correct Answers If the
pressure does not increase after inserting air or ethanol into the
sealed flask using a syringe, it is possible that there is a leak in
