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Organic Lab Practical

time limit:t < 30 min - Developed by: David Flosser - Developed on: 2002-05-15 - 10,418 taken - User Rating: 3,7 of 5 - 183 Votes

Organic Lab Practical

Are you an organic lab menace?

Question 1:

Pure benzophenone melts at 48-49 deg. Celsius. What effect on the melting point would a trace of naphthalene have (naphthalene melts at 80-82 deg. C)

	it would raise the mp
	it would have no effect
	it would lower the mp

Question 2:

What effect would a grain of sand have on the benzophenone mentioned in question 1?

	it would raise the mp
	it would have no effect
	it would lower the mp

Question 3:

a. Is water or ligroin better for recrystallizing benzoic acid (PhCOOH)? b. Is water or ligroin better for recrystallizing stilbene (PhC=CPh)?

	a. ligroin b. water
	a. ligroin b. ligroin
	a. water b. ligroin
	a. water b. water
	a. water b. ligroin

Question 4:

Which of the following is done first in the recrystallization procedure?

	decolorize the solution
	choose a suitable solvent
	dry the product
	induce crystallization by cooling and/or scratching
	filter the product

Question 5:

You are given a sample that is slightly impure. When you determine the melting point, it melts at 51-55 deg. C. You are told that the compound is either benzophenone (mp 49-51 deg. C), maleic anhydride (mp 54-56 deg. C), 2-nitroaniline (mp 71-73 deg. C), or naphthalene (mp 80-82 deg. C). Which do you think it is?

	maleic anhydride
	naphthalene
	benzophenone
	2-nitroaniline
	it cannot possibly be any of these choices!!!!!

Question 6:

Ethers react with a._______ in the air to form b.________.

	a. oxygen b. explosive trinitrotoluene
	a. nitrogen b. flammable nitroethers
	a. oxygen b. explosive peroxides
	a. hydrogen b. fire
	a. ozone b. a violent reaction

Question 7:

After performing a recrystallization, where are the impurities found after the recrystallization?

	in the filter paper
	they evaporate
	on the surface of the pure crystals
	in the filtrate
	they are converted to innocuous materials

Question 8:

What is a common stationary phase in column chromatographY?

	iron (III) chloride
	magnesium oxide
	alumina
	sodium sulfate
	potassium carbonate

Question 9:

In normal column chromatography, what would you do to shift the equilibrium from the solid stationary phase to the liquid mobile phase?

	use more polar mobile phase
	use less polar mobile phase
	increase the amount of mobile phase
	reduce the amount of stationary phase
	it cannot be done

Question 10:

What is the most common mobile phase in gas chromatography?

	krypton
	hexane
	benzene
	helium
	carbon tetrachloride

Question 11:

Which of the following analytical techniques measures the energy of electronic excitation by 200-800 nm light and is also used to infer conjugation and quantify amounts of a compound?

	NMR
	IR
	mass spec
	GC-MS
	UV-Vis

Question 12:

Which of the following is a bad idea during column chromatography?

	dissolve the sample of interest in the minimum of solvent before applying to the column
	make a slurry of alumina and solvent to load into the column
	allow the mobile phase to go 1 inch below the top of the column before adding your sample
	put a layer of sand on top of the column
	collect small fractions (within reason)

Question 13:

Simple distillation is more useful when the compounds boiling points are:

	more than 5 degrees apart
	more than 25 degrees apart
	more than 45 degrees apart
	more than 75 degrees apart
	more than 200 degrees apart

Question 14:

Methanol boils at 65 deg. C and 1-butanol boils at 117 deg. C. How would you separate them?

	fractional distillation
	simple distillation
	TLC
	liquid-liquid extraction
	GC-MS

Question 15:

What would you use to extract benzoic acid from a mixture of phenol, aniline, and methoxybenzene in dichloromethane?

	NaHCO3 (aq)
	NaOH (aq)
	HCl (aq)
	chloroform
	ether

Question 16:

After accomplishing the goal of question 15, how would you extract the phenol?

	NaOH (aq)
	NaHCO3 (aq)
	HCl (aq)
	chloroform
	ether

Question 17:

How would you extract the aniline

	NaHCO3 (aq)
	NaOH (aq)
	HCl (aq)
	chloroform
	ether

Question 18:

Which of the following is not applicable to thin layer chromatography?

	Rf
	mobile phase
	triple point
	solvent front
	development

Question 19:

How are TLC spots typically visualized?

	IR glasses
	UV light
	microscope
	I.O.N. chamber
	silver nitrate bath

Question 20:

Rf is calculated by:

	distance solvent travels - distance spot travels
	distance solvent travels + distance spot travels
	product of distance spot travels and distance solvent travels
	distance spot travels divided by TLC factor (from table)
	distance spot travels/distance solvent travels

Question 21:

Arange the following in order of increasing Rf in TLC: octanoic acid, decane, 1-pentanol

	decane, 1-pentanol, octanoic acid
	1-pentanol, decane, octanoic acid
	decane, octanoic acid, 1-pentanol
	octanoic acid, 1-pentanol, decane
	octanoic acid, decane, 1-pentanol

Question 22:

The nitrogen rule is commonly applied in:

	NMR
	IR
	UV-Vis
	mass spectroscopy
	GC

Question 23:

GC can be used to quantify relative amounts of organic compounds after accounting for:

	molecular weights
	extent of conjugation
	relative response factors
	boiling points
	vapor pressures

Question 24:

The boiling points of water and 2-methyl-2-propanol are 100 deg. C and 82.2 deg. C, respectively. Which has the lower vapor pressure at room temperature?

	2-methyl-2-propanol
	both have the same vapor pressure at room temperature
	water

Question 25:

Which is not a commonly used drying agent?

	sodium sulfate
	magnesium sulfate
	cesium fluoride
	calcium chloride
	drierite

Question 26:

Sublimation is

	passing from the liquid to solid phase
	passing from the liquid to gas phase
	passing from the gas to solid phase
	condensing into the liquid phase
	passing from the solid to gas phase

Question 27:

How can you tell which layer is which during a liquid/liquid extraction?

	smell them
	flame test
	density usually works
	silver spatula test
	Tollen's test

Question 28:

What is the purpose of the packing in fractional distillation?

	provides insulation for the rising vapors
	cools the vapors for collection in the still pot
	prevents flashback and flooding
	provides theoretical plates for multiple distillations
	they provide tensile strength

Question 29:

p-dichlorobenzene boils at 54-56 deg. C; cyclohexane boils at 80.7 deg. C; which will elute from a GC column first?

	cyclohexane
	neither - liquids aren't used in GAS chromatraphy!!!! (wink)
	p-dichlorobenzene

Question 30:

You have a sample that is known to be either benzophenone (has a carbonyl plus aromatics) or naphthalene (only aromatics). What is a quick, easy, spectroscopic way to find out?

	NMR
	mass spec
	UV/Vis
	refractive index
	IR

This Quiz has been designed by David Flosser.