CHEM 232 Lab Final Exam Questions
and Answers
What do you do immediately if there is an accident? (quiz 1) - ANS-notify your instructor
What must you wear every time you do an experiment? (quiz 1) - ANS-safety glasses,
ankle-length pants, upper body coverage (t-shirt ok), blue lab coat, nitrile gloves,
closed-toe shoes, long hair tied up
Where should you dispose any of the wastes during the lab? (quiz 1) - ANS-in the
correct hazardous waste container, usually under the hood in the front of the room
You can use broken glass containers to dispose paper towels. True or false? (quiz 1) -
ANS-False
You finished doing your experiment, but others are not finished yet. You can take off
your glasses and coat and wait. True or false? (quiz 1) - ANS-False
Know functional groups (Identity within a molecule, drawing functional groups together,
etc.) - ANS-Found on page 18-19
What is the equation for degree of unsaturation? - ANS-DU =2C - H - X + N + 2/ 2
use to create isomers
Why do we put filtered solution first at room temperature to cool it down and then in an
ice bath, instead of putting it in an ice bath directly and saving some time? (quiz 2) -
ANS-cooling the filtered solution slowly allows for the formation of better quality crystals
What is the main reason that we care about the melting point of a solid? (quiz 2) - ANS-
to know whether the solid is a pure substance. If it is unpure, we will not find the correct
melting point
Why do we heat up our solvents after recrystallizations? (quiz 2) - ANS-Because the
solute is more likely to dissolve at higher temperatures. This will eventually give us a
better percent yield for recrystallization
Why do we use boiling chips when heating up the solution? (quiz 3) - ANS-to boil the
solution calmly and avoid bumping the liquid out. It also relatively speeds up boiling
process
, Why should we refrain from shaking the solution in the seperatory funnel too hard? -
ANS-too vigorous shaking results in the formation of an emulsion which makes
separation extremely difficult. To fix this issue, add a saturated solution of NaCl to break
up the emulsion
What will happen when you add water to an organic layer? - ANS-the water will rest on
top; the bottom layer will be organic
What are the usual organic solvents available in lab? - ANS-hexane, benzene, diethyl
ether, dichloromethane, and ethyl acetate
Why are diethyl ether and dichloromethane excellent organic solvents? - ANS-They
dissolve most organic compounds and have low boiling points, hence removal of
solvent becomes much easier
What are the two most commonly used drying agents? - ANS-Anhydrous sodium sulfate
and anhydrous magnesium sulfate
Why do we need drying agents? - ANS-the organic phase obtained during extraction will
always have trace amounts of water which need to be removed to obtain the most pure
sample. A drying agent will help remove this water
How much drying agent should be added? - ANS-It depends on a few things:
1) the type of drying agent selected
2) the organic phase
3) if a layer of water is still visible (in this case repeat separation in a separatory funnel)
4) the amount of solvent involved
Why don't we want to use filter paper when drying organic liquids? - ANS-severe loss of
product will occur due to the paper retaining the organic liquid
What is distillation? (Exp. 2) - ANS-a process in which liquid is converted into vapor by
heating (boiling) and then condensing the vapor back to liquid in a separate vessel
What is boiling point? (Exp. 2) - ANS-the point at which all liquid is converted into vapor
without any further change in temperature
What happens when a pure compound is distilled? (Exp. 2) - ANS-the head temperature
(thermometer reading of the distilling vapor) will be the same as the pot temperature
(boiling liquid in flask)
If there are impurities, the pot temperature will have to be raised to allow the substance
to boil
What is Raoult's Law? (Exp. 2) - ANS-partial pressure of A = mole fraction of A x vapor
pressure pure APa = Xa P°a
and Answers
What do you do immediately if there is an accident? (quiz 1) - ANS-notify your instructor
What must you wear every time you do an experiment? (quiz 1) - ANS-safety glasses,
ankle-length pants, upper body coverage (t-shirt ok), blue lab coat, nitrile gloves,
closed-toe shoes, long hair tied up
Where should you dispose any of the wastes during the lab? (quiz 1) - ANS-in the
correct hazardous waste container, usually under the hood in the front of the room
You can use broken glass containers to dispose paper towels. True or false? (quiz 1) -
ANS-False
You finished doing your experiment, but others are not finished yet. You can take off
your glasses and coat and wait. True or false? (quiz 1) - ANS-False
Know functional groups (Identity within a molecule, drawing functional groups together,
etc.) - ANS-Found on page 18-19
What is the equation for degree of unsaturation? - ANS-DU =2C - H - X + N + 2/ 2
use to create isomers
Why do we put filtered solution first at room temperature to cool it down and then in an
ice bath, instead of putting it in an ice bath directly and saving some time? (quiz 2) -
ANS-cooling the filtered solution slowly allows for the formation of better quality crystals
What is the main reason that we care about the melting point of a solid? (quiz 2) - ANS-
to know whether the solid is a pure substance. If it is unpure, we will not find the correct
melting point
Why do we heat up our solvents after recrystallizations? (quiz 2) - ANS-Because the
solute is more likely to dissolve at higher temperatures. This will eventually give us a
better percent yield for recrystallization
Why do we use boiling chips when heating up the solution? (quiz 3) - ANS-to boil the
solution calmly and avoid bumping the liquid out. It also relatively speeds up boiling
process
, Why should we refrain from shaking the solution in the seperatory funnel too hard? -
ANS-too vigorous shaking results in the formation of an emulsion which makes
separation extremely difficult. To fix this issue, add a saturated solution of NaCl to break
up the emulsion
What will happen when you add water to an organic layer? - ANS-the water will rest on
top; the bottom layer will be organic
What are the usual organic solvents available in lab? - ANS-hexane, benzene, diethyl
ether, dichloromethane, and ethyl acetate
Why are diethyl ether and dichloromethane excellent organic solvents? - ANS-They
dissolve most organic compounds and have low boiling points, hence removal of
solvent becomes much easier
What are the two most commonly used drying agents? - ANS-Anhydrous sodium sulfate
and anhydrous magnesium sulfate
Why do we need drying agents? - ANS-the organic phase obtained during extraction will
always have trace amounts of water which need to be removed to obtain the most pure
sample. A drying agent will help remove this water
How much drying agent should be added? - ANS-It depends on a few things:
1) the type of drying agent selected
2) the organic phase
3) if a layer of water is still visible (in this case repeat separation in a separatory funnel)
4) the amount of solvent involved
Why don't we want to use filter paper when drying organic liquids? - ANS-severe loss of
product will occur due to the paper retaining the organic liquid
What is distillation? (Exp. 2) - ANS-a process in which liquid is converted into vapor by
heating (boiling) and then condensing the vapor back to liquid in a separate vessel
What is boiling point? (Exp. 2) - ANS-the point at which all liquid is converted into vapor
without any further change in temperature
What happens when a pure compound is distilled? (Exp. 2) - ANS-the head temperature
(thermometer reading of the distilling vapor) will be the same as the pot temperature
(boiling liquid in flask)
If there are impurities, the pot temperature will have to be raised to allow the substance
to boil
What is Raoult's Law? (Exp. 2) - ANS-partial pressure of A = mole fraction of A x vapor
pressure pure APa = Xa P°a
