Lab Quizzes

How are colored impurities removed?

charcoal

how are insoluble impurities removed?

hot gravity filtration and recrystallization

you should add a few boiling chips before heating liquids to their boiling point

True

Can solid be added to a solution near its boiling point?

No

which will end up purer, fast growing crystals or slow growing crystals

slow growing crystals

mixed melting point identification

Mix powder of a known and unknown compound together. If melting point depresses, the compounds are different, if the melting point remains the same then the compounds are identical.

What piece of glassware is used for microscale recrystallization?

Craig Tube

What causes color in organic compounds?

conjugated pi systems

What should the filtrate collected after hot gravity filtration look like? (Exp 1)

colorless and clear

__ solution may be poured down the sink

aqueous

__ waste should be poured into a non-halogenated waste container

organic

liquid-liquid extraction

separation of compounds using two immiscible solvents

Will the upper layer always be organic?

No, depends on density

Which is more efficient, multiple extractions or a single extraction

multiple extractions

Are neutral organic bases and acids soluble in organic solvents?

No

Drying agent (exp 2)

sodium sulfate

Why are drying agents necessary?

removes any moisture left after extraction

Funnel used in Exp 2

Hirsch Funnel

Why is MtBE (methyl tert-butyl ether) preferred over diethyl ether?

MtBE is less of a fire hazard

two most common adsorbents in TLC

silica gel and alumina

thin layer chromatography relies on a layer of adsorbent as __ phase and ascending solvent as __ phase

stationary; mobile

The more polar the compound, the more it interacts with stationary phase

True

Is silica gel (stationary phase) highly polar?

Yes

Should the TLC plate spot be big or small?

small

Rf depends on temperature

false

Two TLC visualization techniques

UV lamp and Iodine Jar

Why is a piece of filter paper/wick used in the development chamber for TLC?

creates a fully saturated environment in the chamber

What is a reason you may not see spots after running a TLC plate?

Your spotted solution is too dilute.

Rf calculation

distance from origin to center of the spot/distance from origin to the solvent front

Eluent (column chromatography)

the mobile phase or solvent that is used to pass through the column and separate the components of a mixture based on their interaction with the stationary phase

why is it important to switch solvents when eluting components through the column?

The components differ in polarity, so solvents of different polarities are needed

In column chromatography, will the more polar or less polar compound elute first?

The less polar compound, because the more polar one is slowed by interaction with the stationary phase.

Do compounds that interact weakly with stationary phase move slowly?

No

Should the column run dry once you have started it?

No

two column packing methods

Wet and dry column packing

When is simple distillation used?

Separation of a mixture of two volatile liquids with close boiling points.

Is simple or fractional distillation more efficient?

Fractional - it goes through multiple vaporization/condensation cycles as opposed to just one with simple distillation

Should a closed vessel be heated?

No

Should distillation be rapid?

No

What method is used to determine the % composition of distilled liquids?

gas chromatography

Water condenser

water enters from the lower inlet and flows out the top inlet

when two immiscible liquids are mixed together in a heterogenous mixture, total pressure of system is given by

P*total = P*a + P*b

What would happen if eugenol was distilled directly?

it would decompose due to the high temperature required

Steam Distillation temperature

below 100C

Are essential oils miscible with water

No (immiscible)

What happens in steam distillation?

organic compound is co-distilled with water

Where is the distillate collected during distillation?

Hickman head

Eugenol is

both a terpene and a phenol

Drying agent

Sodium Sulfate

boiling point cyclohexanol

161 C

Dehydration byproduct

water

What are acid spills neutralized with

sodium bicarbonate

Dehydrohalogenation of alcohol can occur by

E1 and E2

What medium does dehydration of an alcohol occur at?

highly acidic

Dehydrating agent (exp 5)

any strong acid

Purpose of drying tube in Exp 5

contains odor

Work Up

crude mixture is purified and isolated

Characterization

a purified substance is identified both quantitatively and qualitatively