CHEM 232 LAB PRACTICAL EXAM QUESTIONS ANSWERED CORRECTLY LATEST UPDATE 2026
supersaturation is necessary for: - Answers crystallization
which statement is true about "purification" - Answers It increases purity, often with some yield loss
why should the TLC solvent front be marked immediately after removing the plate? - Answers
because the solvent evaporates quickly and the front becomes invisible
what is the purpose of a distillation head? - Answers direct vapor to condenser and hold
thermometer
what is the purpose of gravity filtration during recrystallization? - Answers remove insoluble
impurities
why must charcoal be removed before crystallization? - Answers prevent absorption of product
overpacking a capillary tube tends to: - Answers broaden mp and give inaccurate values
If the unknown is one of three analgesics, the "pairing" standards should be: - Answers The three
candidate analgesics
In SN2, inversion occurs because: - Answers Backside attack minimizes repulsion with leaving group
Which factor affects solubility most strongly? - Answers Temperature
If too much solvent is used, one way to improve yield is to: - Answers consecrate by evaporating
some solvent, then cool again
What is supersaturation? - Answers More solute dissolved than expected
Rearrangements are possible in: - Answers E1 reactions
Which base is weak but still allows E1? - Answers Water
Why should solution be removed from heat before cooling? - Answers All of the answers are correct
When collecting fractions, you should label: - Answers Each fraction with number and temperature
range
When does the distillation temperature typically end? - Answers When the last drop is collected (or
temperature rises sharply after main fraction)
How can oiling out sometimes be corrected? - Answers Add more solvent
The primary purpose of measuring melting point after purification is to: - Answers Asses purity and
help identify the compound
What is the main purpose of column chromatography in this lab? - Answers Separate and purify
compounds in a mixture
The temperature you record as the "boiling point range" in distillation is based primarily on the: -
Answers Head temperature
If you must use a solvent pair, you add the poor solvent until: - Answers Slight cloudiness persists
when hot, then clear on warming
If vacuum is suddenly lost during vacuum distillation, the boiling point will: - Answers Increase
Which factor most strongly controls crystal size? - Answers Cooling rate
In nucleophilic substitution labs, the function of stirring is primarily to: - Answers Improve mixing and
contact of reactants
If the distillation rate is uneven (spurting), you should: - Answers Adjust heat to maintain steady
boiling
Why are crystals sometimes recrystallized more than once? - Answers Increase purity
Which alkene us most substituted? - Answers 2-methyl-2-butene
A flow rate that is too fast tends to: - Answers Reduce interaction time and worsen separation
Why does the reaction mixture need to be refluxed? - Answers To drive the reaction to completion by
providing consistent heat
Which solvent property affects recrystallization most? - Answers Polarity
Why should recrystallization be done before melting point analysis? - Answers Improve accuracy
Distillation separates compounds mainly based on differences in: - Answers Boiling point/vapor
pressure
If your "pure" fraction still gives a streak on TLC, it suggests: - Answers Overloading, impurities, or
poor solvent choice
If your target compound is not eluting at all, the best first adjustment is to: - Answers Increase
solvent polarity
If a solution cools too quickly, it may: - Answers Trap impurities and form small crystals
A mixed-solvent recrystallization is useful when: - Answers No single solvent has ideal temperature
dependent solubility
supersaturation is necessary for: - Answers crystallization
which statement is true about "purification" - Answers It increases purity, often with some yield loss
why should the TLC solvent front be marked immediately after removing the plate? - Answers
because the solvent evaporates quickly and the front becomes invisible
what is the purpose of a distillation head? - Answers direct vapor to condenser and hold
thermometer
what is the purpose of gravity filtration during recrystallization? - Answers remove insoluble
impurities
why must charcoal be removed before crystallization? - Answers prevent absorption of product
overpacking a capillary tube tends to: - Answers broaden mp and give inaccurate values
If the unknown is one of three analgesics, the "pairing" standards should be: - Answers The three
candidate analgesics
In SN2, inversion occurs because: - Answers Backside attack minimizes repulsion with leaving group
Which factor affects solubility most strongly? - Answers Temperature
If too much solvent is used, one way to improve yield is to: - Answers consecrate by evaporating
some solvent, then cool again
What is supersaturation? - Answers More solute dissolved than expected
Rearrangements are possible in: - Answers E1 reactions
Which base is weak but still allows E1? - Answers Water
Why should solution be removed from heat before cooling? - Answers All of the answers are correct
When collecting fractions, you should label: - Answers Each fraction with number and temperature
range
When does the distillation temperature typically end? - Answers When the last drop is collected (or
temperature rises sharply after main fraction)
How can oiling out sometimes be corrected? - Answers Add more solvent
The primary purpose of measuring melting point after purification is to: - Answers Asses purity and
help identify the compound
What is the main purpose of column chromatography in this lab? - Answers Separate and purify
compounds in a mixture
The temperature you record as the "boiling point range" in distillation is based primarily on the: -
Answers Head temperature
If you must use a solvent pair, you add the poor solvent until: - Answers Slight cloudiness persists
when hot, then clear on warming
If vacuum is suddenly lost during vacuum distillation, the boiling point will: - Answers Increase
Which factor most strongly controls crystal size? - Answers Cooling rate
In nucleophilic substitution labs, the function of stirring is primarily to: - Answers Improve mixing and
contact of reactants
If the distillation rate is uneven (spurting), you should: - Answers Adjust heat to maintain steady
boiling
Why are crystals sometimes recrystallized more than once? - Answers Increase purity
Which alkene us most substituted? - Answers 2-methyl-2-butene
A flow rate that is too fast tends to: - Answers Reduce interaction time and worsen separation
Why does the reaction mixture need to be refluxed? - Answers To drive the reaction to completion by
providing consistent heat
Which solvent property affects recrystallization most? - Answers Polarity
Why should recrystallization be done before melting point analysis? - Answers Improve accuracy
Distillation separates compounds mainly based on differences in: - Answers Boiling point/vapor
pressure
If your "pure" fraction still gives a streak on TLC, it suggests: - Answers Overloading, impurities, or
poor solvent choice
If your target compound is not eluting at all, the best first adjustment is to: - Answers Increase
solvent polarity
If a solution cools too quickly, it may: - Answers Trap impurities and form small crystals
A mixed-solvent recrystallization is useful when: - Answers No single solvent has ideal temperature
dependent solubility
