CHM2210L Midterm Exam Questions and
Answers 100% Solved | Graded A+
Do all mixtures of two different organic compounds exhibit a broad melting
point range? - ✔✔No, eutectic mixtures(minimum mp for a mixture) melt
with a sharp mp range.
Do organic compounds that exhibit polymorphism have different melting
points? - ✔✔Yes, variations in the intermolecular attraction of different
crystalline forms can cause polymorphs to have different but sharp mp
What might you observe when an organic compound melts with
decomposition? - ✔✔Darkening, change in color, effervesence
What characteristic in melting point behavior does an impure organic
compound usually exhibit? - ✔✔A broad and depressed mp range
Given that your unknown was one of those listed on page 1-8, if you
obtained a corrected melting point range of 68-70°C, could you definitely
identify what your unknown was? - ✔✔According to the information, the
unknown could either be benzhydrol,phenyl benzoate, or biphenyl. After
1
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,performing a mix-melting experiment than you would be able to identify
your unknown.
When should the start of the melt be recorded?* - ✔✔When the first
appearance of liquid within the bulk of the sample is seen.
A compound is observed to melt sharply at 111°C with the vigorous
evolution of a gas; then the compound solidified and did not melt until
155°C sharply. Explain. - ✔✔Some organic compounds undergo
'elimination' reactions when heated, losing such small molecules as H2O or
CO2 and yielding other organic products. In this case,
A → B + gas
mp = 111d mp= 155
d= decomposition
Suppose that your sample melts before you are ready to record the melting
point. Should you cool capillary and redetermine the melting point, or begin
with a fresh sample? Explain - ✔✔Start with a fresh sample; many organic
compounds melt with at least some decomposition- or when cooled, solidify
2
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
, in a different polymorphic form, and thus would exhibit a different mp from
that of the original sample.
Why is it not good practice to mix two components by simply stirring them
together and then sampling them for a mixed melting point? - ✔✔Stirring
two solid components together does not yield a homogenous mixture. A
small sample for a mp determination might thus be practically 100% of one
component.
Give a reason for using the technique.
A- The rate of heating is adjusted to no more than 4° per minute when the
solid is melting
B- The capillary tube is filled with no more than 2mm of sample.
C- The sample is firmly packed into the capillary tube. - ✔✔A-If the
temperature is increased too rapidly at the melting point, the thermometer,
sample, and heating block will not be at thermal equilibrium, and an
erroneously depressed & wide mp range will be observed.
B- Too much sample will take longer to melt and exhibit an erroneously
large and higher melting point range will be observed.
3
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
Answers 100% Solved | Graded A+
Do all mixtures of two different organic compounds exhibit a broad melting
point range? - ✔✔No, eutectic mixtures(minimum mp for a mixture) melt
with a sharp mp range.
Do organic compounds that exhibit polymorphism have different melting
points? - ✔✔Yes, variations in the intermolecular attraction of different
crystalline forms can cause polymorphs to have different but sharp mp
What might you observe when an organic compound melts with
decomposition? - ✔✔Darkening, change in color, effervesence
What characteristic in melting point behavior does an impure organic
compound usually exhibit? - ✔✔A broad and depressed mp range
Given that your unknown was one of those listed on page 1-8, if you
obtained a corrected melting point range of 68-70°C, could you definitely
identify what your unknown was? - ✔✔According to the information, the
unknown could either be benzhydrol,phenyl benzoate, or biphenyl. After
1
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
,performing a mix-melting experiment than you would be able to identify
your unknown.
When should the start of the melt be recorded?* - ✔✔When the first
appearance of liquid within the bulk of the sample is seen.
A compound is observed to melt sharply at 111°C with the vigorous
evolution of a gas; then the compound solidified and did not melt until
155°C sharply. Explain. - ✔✔Some organic compounds undergo
'elimination' reactions when heated, losing such small molecules as H2O or
CO2 and yielding other organic products. In this case,
A → B + gas
mp = 111d mp= 155
d= decomposition
Suppose that your sample melts before you are ready to record the melting
point. Should you cool capillary and redetermine the melting point, or begin
with a fresh sample? Explain - ✔✔Start with a fresh sample; many organic
compounds melt with at least some decomposition- or when cooled, solidify
2
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
, in a different polymorphic form, and thus would exhibit a different mp from
that of the original sample.
Why is it not good practice to mix two components by simply stirring them
together and then sampling them for a mixed melting point? - ✔✔Stirring
two solid components together does not yield a homogenous mixture. A
small sample for a mp determination might thus be practically 100% of one
component.
Give a reason for using the technique.
A- The rate of heating is adjusted to no more than 4° per minute when the
solid is melting
B- The capillary tube is filled with no more than 2mm of sample.
C- The sample is firmly packed into the capillary tube. - ✔✔A-If the
temperature is increased too rapidly at the melting point, the thermometer,
sample, and heating block will not be at thermal equilibrium, and an
erroneously depressed & wide mp range will be observed.
B- Too much sample will take longer to melt and exhibit an erroneously
large and higher melting point range will be observed.
3
©NINJANERD 2025/2026. YEAR PUBLISHED 2025.
