Lab 3 Flashcards
(22 cards)
T/F: Melting point should be recorded as an exact temperature.
False- should be recorded as a range
What influences melting point?
Sample purity
When doing a rough melting point, you want to set the ramp rate to _________
. After this measurement is finishes, you should set ________________
your observed rough melting point and chose a ramp rate of
____________
to obtain your precise melting point measurement.
10 degrees/min, slightly closer to, 1 degree/min
The low temperature of a melting point measurement corresponds to the…
Moistening point
I run a melting point experiment in the lab. In my fast measurement, I observe my solid slightly changing at 123 °C, then liquid sample appears at 124 °C. I see a meniscus form at 126 °C and the sample melts completely at 127 °C. Then, I run a slow measurement where I observe slight change and liquid appearing at 123 °C. A meniscus forms at 124 °C and the sample becomes clear at 125 °C.
What should I mark down as the accurate melting point of this sample?
123-125
The melting point range of an impure compound will be…
Lower/broader
T/F- You can dispose of used melting point capillaries in the normal trashcan.
False
T/F- You cannot reuse melting point samples.
True
What is the primary purpose of infrared (FTIR) spectroscopy in chemical analysis?
To identify functional groups in a molecule
Fourrier Transform Infrared Spectroscopy (FTIR) observes what kind of molecular motion?
Vibrations
FTIR spectra are given in what units?
wavenumbers (cm⁻¹)
When you are done with your IR, you should clean your plates with
Acetone and kimwipes
Water in your sample would show as (IR)
A large, broad peak at 3500 cm⁻¹
IR GROUP CHART
What is the difference between the “fingerprint region” and the “functional group region” in an IR spectrum?
The fingerprint region is unique to each molecule and shows complex, overlapping absorptions, while the functional group region shows characteristic absorption bands for functional groups.
The salt plates used in this experiment do not absorb IR radiation. t/f
True
t/f FTIR can visualize ALL covalent bond vibrations.
False
What is the primary purpose of ¹H NMR Spectroscopy?
To elucidate the structure of organic compounds
T/f all types of atoms are visible by NMR
False
Which of the following affect a 1H nucleus’ chemical shift, in ppm?
Aromatic rings, e- - atoms, resonance structures
What does the integration of a peak in a ¹H NMR Spectrum represent?
The number of protons contributing to that peak
You can use normal chloroform (CHCl₃) as the solvent for your NMR sample. t/f
F
