CHEM 281 EXAM- VIRTUAL LAB QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026
Dehydration is removal of: - Answers 2 H atoms and 1 O atom
If a student mixed up their product cyclohexane and reactant cyclohexanol, what methods could we
use to tell them apart? - Answers 1. Add bromine water (alkenes decolourize)
2. Add sodium metal to dried samples of both (H gas produced when Na reacts with alcohol)
3. Measure each sample's boiling point
4. IR spectroscopy on both
If cyclohexanol was dehydrated to cyclohexane with a 100% of reactants converted to products, how
would the mass of the product compare with the reactant? - Answers Product has less mass than
reactant
What is the formula of phosphoric acid? - Answers H3PO4
In set up of apparatus, where should bulb of thermometer be properly placed? - Answers In still head
directly opposite opening of condenser
In the virtual lab, how is the dehydration of alcohol accomplished? - Answers By heating the alcohol
with phosphoric or sulfuric acid
At temperature should you collect liquid? - Answers 70-90 degrees C
- specifically collect cyclohexane that distills over around 80-85 degrees C
What solution do you add to cooled distillate in separating funnel? - Answers Saturated NaCl
What is the best description of a distillation? - Answers A mixture of liquids is heated and when
BP of the required liquid is reached, the resulting condensing liquid is collected
How much should you heat the liquid in a distillation? - Answers Only enough to keep the liquid
gently boiling
What should you add to the solution to aid gentle boiling? - Answers Anti bumping-granules or
magnetic follower
What should you never add anti bumping granules to? - Answers Hot liquids
When using a condenser, should liquid flow from the top or bottom? - Answers Bottom of condenser
How can a simple distillation be modified to improve separation of two liquids with boiling points <20
degrees apart? - Answers Use a fractioning column
What does the condenser do? - Answers Cools vapour, turning it back to a liquid
What happens if you boil too vigorously? - Answers Mixed fractions containing impurities can boil
over into collection flask
How fast should liquids be condensing into the collection flask? - Answers 1-2 drops per second
Boiling flask should never be more than __% full - Answers 50
What is reflux? - Answers Technique used to heat volatile materials without any loss of reactant or
product.
-Reaction vessel (pear shaped flask) fitted with condenser so that vapours from flask fall back into the
heated mixture
Why should you never clamp the condenser? Where should you clamp instead? - Answers
Connection to flask can be broken this way.
Only clamp the neck of the flask
What should the maximum volume of the flask be? - Answers Half full
How far up condenser should condensing occur? - Answers 2/3rds
Should the top of the condenser be stoppered? - Answers NO, this creates a closed system
What is an appropriate use for reflux? - Answers To carry out a reaction that requires heating
Out of the following, which substances do not dissolve in water?
Hydrophilic
Hydrophobic
Lipphilic
Lipophobic - Answers Hydrophobic & lipophillic b/c non polar
What is the likely density of an impure aq. solution? - Answers 1g/cm3, the density of water
What is the theoretical yield of the product of 2-methylhexanol (5mL, d=0.929g/mL, MW=114.19)
heated under reflux with 5mL of 85% phosphoric acid. - Answers 3.9g
What is the %yield equation? - Answers %yield= (mass of product/possible max of product) x 100
What equations are necessary to know for theoretical yield calculation? - Answers n=m/Mw
d=m/v
Dehydration is removal of: - Answers 2 H atoms and 1 O atom
If a student mixed up their product cyclohexane and reactant cyclohexanol, what methods could we
use to tell them apart? - Answers 1. Add bromine water (alkenes decolourize)
2. Add sodium metal to dried samples of both (H gas produced when Na reacts with alcohol)
3. Measure each sample's boiling point
4. IR spectroscopy on both
If cyclohexanol was dehydrated to cyclohexane with a 100% of reactants converted to products, how
would the mass of the product compare with the reactant? - Answers Product has less mass than
reactant
What is the formula of phosphoric acid? - Answers H3PO4
In set up of apparatus, where should bulb of thermometer be properly placed? - Answers In still head
directly opposite opening of condenser
In the virtual lab, how is the dehydration of alcohol accomplished? - Answers By heating the alcohol
with phosphoric or sulfuric acid
At temperature should you collect liquid? - Answers 70-90 degrees C
- specifically collect cyclohexane that distills over around 80-85 degrees C
What solution do you add to cooled distillate in separating funnel? - Answers Saturated NaCl
What is the best description of a distillation? - Answers A mixture of liquids is heated and when
BP of the required liquid is reached, the resulting condensing liquid is collected
How much should you heat the liquid in a distillation? - Answers Only enough to keep the liquid
gently boiling
What should you add to the solution to aid gentle boiling? - Answers Anti bumping-granules or
magnetic follower
What should you never add anti bumping granules to? - Answers Hot liquids
When using a condenser, should liquid flow from the top or bottom? - Answers Bottom of condenser
How can a simple distillation be modified to improve separation of two liquids with boiling points <20
degrees apart? - Answers Use a fractioning column
What does the condenser do? - Answers Cools vapour, turning it back to a liquid
What happens if you boil too vigorously? - Answers Mixed fractions containing impurities can boil
over into collection flask
How fast should liquids be condensing into the collection flask? - Answers 1-2 drops per second
Boiling flask should never be more than __% full - Answers 50
What is reflux? - Answers Technique used to heat volatile materials without any loss of reactant or
product.
-Reaction vessel (pear shaped flask) fitted with condenser so that vapours from flask fall back into the
heated mixture
Why should you never clamp the condenser? Where should you clamp instead? - Answers
Connection to flask can be broken this way.
Only clamp the neck of the flask
What should the maximum volume of the flask be? - Answers Half full
How far up condenser should condensing occur? - Answers 2/3rds
Should the top of the condenser be stoppered? - Answers NO, this creates a closed system
What is an appropriate use for reflux? - Answers To carry out a reaction that requires heating
Out of the following, which substances do not dissolve in water?
Hydrophilic
Hydrophobic
Lipphilic
Lipophobic - Answers Hydrophobic & lipophillic b/c non polar
What is the likely density of an impure aq. solution? - Answers 1g/cm3, the density of water
What is the theoretical yield of the product of 2-methylhexanol (5mL, d=0.929g/mL, MW=114.19)
heated under reflux with 5mL of 85% phosphoric acid. - Answers 3.9g
What is the %yield equation? - Answers %yield= (mass of product/possible max of product) x 100
What equations are necessary to know for theoretical yield calculation? - Answers n=m/Mw
d=m/v
