question

_____ is an important technique for the physical separation of solids and liquids

answer

filtration

question

one of the purposes of filtration in the organic laboratory is to separate a ___ from a ___ or ___

answer

solid product; reaction mixture; recrystallization solution

question

one of the purposes of filtration in the organic chemistry laboratory is to remove ____ from a solution

answer

solid impurities

question

one of the purposes of filtration in the organic chemistry laboratory is to separate a _____ from a ___ after an ___

answer

product solution; dry agent; aqueous extration

question

the miniscale filtrations commonly performed in the organic laboratory use ___ and ___ for gravity filtration

answer

conical funnels; Erlenmeyer flasks

question

the miniscale filtrations commonly performed in the organic laboratory use ___or ___ and ___ for vacuum filtration

answer

Buchner; Hirsch funnels; filter flasks

question

conical funnels, buchner funnels and hirsch funnels all require the use of ____ to separat the solid from the liquid in the mixture undergoing filtration unless a funnel with a ____ is used

answer

filter paper; glass frit

question

The liquid that passes through the filter paper or glass frit is called the ____. The solid is called the ___.

answer

filtrate; precipitate

question

Microscale gravity filtrations are usually done with a ____ pipet packed with either ___, ___ or ____.

answer

Pasteur pipet; cotton; glass; wool

question

Filter paper is used for ___ filtrations

answer

grvity; vacuum

question

whatman filter paper no ____ works for both gravity and vacuum filtrations

answer

2

question

When a filtrate contains the desired product and the solid being filter is a by-product a ____ filter paper such as ____ can be used

answer

a fast; hardened; Whatman 54

question

When an emulsion forms during an extraction ____ filtration through _____ paper will usually break the emulsion

answer

vacuum; phase separator filter

question

Whatman 1PS is a _____ filter paper

answer

phase separated

question

______ filter paper provides a larger surface for liquid-solid separation, which facilitates faster gravity filtration than does the usual ____

answer

fluted; filter paper cone

question

Faster filtration is especially important when filtering insoluble impurities from a ____ solution in order to prevent crystallization as the solution ____

answer

hot recrystallization; cools

question

Vacuum filtration does not work well for a hot solution because much of the soluvant can be lost to ___ and because the solution cools too ____ leading to premature ____

answer

evaporation; rapidly; crystallization

question

To make a fluted filter crease a regular paper in half ___ times then fold each of the eight sections of paper inward so that it looks like an accordian

answer

4

question

_____ can be used instead of paper filters for vacuum filtration with buchner or Hirsh funnels, which have a horizontal surface perforated with small holes

answer

glass fiber filters

question

_____mm glass fiber circles work well with Hirsch funnels ____ sizes can be used with Buchner funnels

answer

13-24; larger

question

Why might you want to use glass fiber filters even if they are expensive

answer

they are particularly useful if the particles of solid being filtered are very small

question

Cotton or glass wool can be packed into a Pasteyr pipet to make a useful filter in ____ or _____ filtrations

answer

small scale; microscale

question

Samples of analysis by _____, _____ or ____ may contain very fine particulates that would interfere with a measurement

answer

NMR spectroscopy; polarimetry; high pressure liquid chromatography

question

A micropore filter will remove particles as small as ____

answer

0.5 micrometers

question

When using a micropore filter draw a liquid sample into a ___- and ____. Invert it so that the filter points ___ and push the plunger just enough to force a few drops through the filter. Then reposition the filter pointing down and place it over a receiving vial. Press the plunger to force the solution through the filter into a vial

answer

syringe; attach a micropore filter to its end; upwards

question

A filter aid should only be used for a mixture where the filtrate will contain ____ and the solid adhering to the filter aid ____

answer

the desired material

question

example of filter aid

answer

Celite

question

If a hot mixture which is being filtered contains a dissolved solid you must take the necessary precautions to prevent the solid from ____ during the filtration process

answer

crystallizing

question

When you are trying to preent a solid from crystallizing during the filtration process you must first _____ to the receiving flask ( about ____ depending on the size of the flask). You then ___ the flask, __ and ___ in a ____ or clamp the flask in a water bath that is being heated on a hot plate. The hot solvent warms the funnel and helps prevent _____ . If the steam bass is large enough keep both flasks hot during the filtration process. if it is too small for both keep the _____ hot and set the ___ on the bench top. Pour the hot recrystallization solution through the ____

answer

add a small amount of recrystallization solvent; 1-10 mL; heat; funnel; solvent; steam bath; premature crystallization of the solute during filtration; unfiltered solution; receiving flask; fluted filter paper

question

With recrystallization from ___ or ____ the heating can be carried out directly on a hot plate. Do not use a hot plate with ____, however b/c the olvent may burst into flames if it comes into direct contact with a hot surface

answer

water; water-ethanol mixture; low boiling flammable organic solvents

question

____ pipets are exccellent for filtration of small quantities of liquid when the tapered portion of the pipet is packed with glass wool or coton

answer

Pasteur

question

Dispose of pasteur pipets in a -___ box or in a manner that does not present a safety hazord to lab personnel or house keeping staff

answer

sharps

question

When a small amount of organic liquid or solution needs to be separated from a solid that will be discarded a ____ provides the necessary filtration with minimal loss of thee organic liquid

answer

Pasteur filter pipet

question

When using a Pasteur filter pipet if the solid (which is being discarded) contains _____ using glass wool or cotton may not provide sufficient filtration and a ____ is added

answer

very fine particulates; Celite

question

To prepare a filter pipet, use a pair of tweezers to pick up a small amount of cotton and then push it down the pipet with a ___. Pack the coton down firmly in the bottom of the tapered portion of the pipet. Use a ___ to hold the filter pipet in a vertical position for filtration and place a small flask beneath it. Use anothr ____ to transfer the mixture being filtered to the filter pipet. The drying agent or solid impurties will adhere to the ___. If the concentration of liquid solution is not an important constrant use a clean Pasteur pipet to add ____ of fresh solvent to the filter pipet to rinse all the desired material from it and collect the rinse in the same ____

answer

wooden applicator stick; clamp; Pasteur pipet; cotton; Erlenmeyer flask

question

Vacuum filtration is used to ___ and ___ separate a solid from the liquid with which it is mixed

answer

Vacuum filtration

question

The recovery of a ____ from a recrystallization procedure is a common application of vacuum filtration in the organic chemistry lab.

answer

crysallized

question

Vacuum filtration is employed when it is necessary to use a ___ to remove very finely divide ___ solids from a solution; in this instant it is the -___ not the ___ that is the desired product

answer

filter aid; insoluble; solution; solid

question

The vacuum source for a filtration can be either a ____ or a ___

answer

water aspirator; compressed drive vacuum system

question

____ tubing must be used in vacuum filtration so that the tubing will not collapse from atmospheric pressure on the outside when the vacuum is applied

answer

Heavy walled

question

If the tubing collapses the vacuum filtration will not ___

answer

work

question

Most funnels used for vvacuum filtration have a ____ that holds the filter paper to retain the solid from its accompanying liquid

answer

flat; perforated; or porous plate

question

When using a Buchner or Hirsch funnel with perforations it is crucial to ____ for the funnel you are using

answer

to select the correct size of filter paper

question

How to tell if you selected the right filter paper size for a hirsch or buchner funnel

answer

the paper must lie flat on the perforated plat and just cover all the holes in the plat e but not curl up on the side

question

the apparatus for a miniscale vacuum filtration consists of a ____, ___, ___, ____ or ___

answer

Buchner funnel (or medium sized Hirsch funnel); neoprene adaptor; filter flask; trap flask; bottle

question

A trap flask is placed between the ___ and ___ to prevent back flow of water into the filter flask when the water aspirator is the vacuum source

answer

vacuum source; filter flaskk

question

A trap flask is placed between the vacuum source and the filter flask to prevent ____ into the filter flask when a water aspirator is the vacuum source

answer

back flow of water

question

With a compressor driven vacuum system the trap flask keeps any _____

answer

overflow from the filter flask out of the vacuum pump

question

IN vacuum filtration:both the ____ and the ___ must be firmly clamped to the apparatus from tipping over

answer

filter flask; trap flask

question

The neoprene adaptor ensures a _____

answer

tight seal between the filter flask and teh Buchner funnel

question

Heavy-walled tubing is used to connect the ___ and ___ to prevent collapse of tubing from atmosphereic pressure when the vaccuum is applied

answer

vacuum line; filtration flask

question

When using vacuum filtration after you place the appropriately sized filter paper in the Buchner funnel you must ___ the paper with ___

answer

wet; small amount of the solent

question

Once you've turned on the vacuum source to pull the paper tightly over the holes in the funnel you must ____ pour the mixture into the funnel

answer

immediately

question

At the end of vacuum filtration how do you separate the filter flask and the funnel

answer

use one hand to firmly old the filter flask and the other to tip the funnel slightly to the side to break the seal

question

At the end of vacuum filtration use one hand to firmly old the filter flask and the other to tip the funnel slightly to the side to break the seal before _______

answer

turning off the vacuum

question

Unlike funnels with perforations and filter paper, funnels for vacuum filtration can also have a ____ which need no filter paper

answer

fritted glass disc

question

_--- and ____ sometime provide a more powerful vacuum than is necessary for microscale vacuum filtrations and this can lead to the loss of ____

answer

water aspirators; vacuum pumps; valuable compounds

question

microscale filtration sometimes use a ____ as a vacuum

answer

100mL syringe (pull up on syringe causes vacuum to be formed)

question

A microscale filtration apparatus should always be ____

answer

firmly clamped at the neck of the filter flask or side arm test tube (the apparatus tips easily when it is attached to the heavy-walled rubber tubing leading to the vacuum source)

question

The easiest way to recover the solid after a vacuum filtration is to ____

answer

invert the funnel over a clean watch glass or piece of weighing paper and allow the solid to pour onto the watch glass or paper

question

In vacuum filtration not all of the solid will be release from the paper inside the funnel. Rather than scraping the solid away from the paper which can ____, Use a ____ to reach behind the paper and release it from the perforations or the frit at the bottom of the funnel.Then gently scape everything off

answer

contaminate the product with bits of paper; naaroow flexible spatula

question

If solid recovered from vacuum filtration is wet allow it to ___

answer

dry

question

A liquid can be separated from a few large particles by _____

answer

decanting it

question

_____: process in which a liquid can be separated from a few large particles by carfeully pouring away the liquid above the particles

answer

decanting

question

When a smple contains suspended particles ____ may be more effective than filtration to separate the solid and the liquid

answer

centrifugation

question

Centrifugation is also used to break _____ emulsions in microscale extractions

answer

centrifugation

question

During operation of a centrifuge, the sample tube must be ____ by another centrifuge tube filled with an equal volume of liquid

answer

counterbalance

question

If a solution contains unwanted solid material use _____ to separate the mixture. If the desired product is a solid use ____ to recover it from the liquid. In microscale experiments use a ____ to remove unwanted solid but if the desired material is a solid use ___ to recover it

answer

gravity filtration; vacuum filtration; Pasteur filer pipet; vacuum filtration

question

If your filtrate is cloudy you probably ____

answer

used the wrong type of filter paper

question

In vacuum filtration using filter paper of the ____ can allow oth the liquid and the solid particles to creep around the edges which will lead to incomplete separation

answer

incorrect diameter

question

If you use water to wet the filter paper for the vacuum filtration of a dry organic solution water will ____ and probably resut in a ___

answer

contaminate the filtrate; cloudy filtrate

question

It is always a good idea to start with a ____ before filtering

answer

clean filter

question

During vacuum filtration, the iltered solution can evaporate and become cold. This will change the solubility of the dissolved solute and may cause it to crystallize or precipate from the filtrate. If you are ____ then you don't need to worry about these solids

answer

not collecting the filtrate

question

The pores in the filter paper can become clogged if ____

answer

paper of the wrong porosity is used

question

A ____ is produced by briefly evacuating the filter flask and then isolating it from the vacuum source by pinching the vacuum tubing

answer

passive vacuum

question

Lack of suction in a vacuum filtration is usually caused by the collapse of ____ not designed for use with a vacuum

answer

thin walled tubber tubing

question

If you are not collecting the solid it is often useful to use a ___

answer

filter aid

question

you use a filter aid if you are not collecting the ___

answer

solid

question

Molecules in a crystal are arranged in a _____

answer

regular pattern

question

Melting occurs when the fixed array of molecules in the crystalline solid rearranges to more random, freely moving ____

answer

liquid state

question

The transition from solid to liquid requires energy in the form of ____

answer

heat to break down the crystal lattice

question

The temperature at wihch the transition from solid to liquid is the solids ____

answer

meelting point

question

____ an important physical property for any solid compound

answer

melting point

question

The melting point of a compound is useful in establihing its ___ and as a criterion of its ____

answer

identity; purity

question

until the advent of modern chromatography and spectroscopy the _____ was the primary index of purity for an organic solid

answer

melting point

question

melting points are still used as a preliminary indication of ___

answer

purity

question

The melting range (or more correctly the melting ___) of a crystalline organic compound is determined by the strength of ___

answer

point; intermolecular forces bbetween its molecules

question

types of intermolecular forces

answer

hydrogen bonds; dipole-dipole interactions; van der Waals interaction

question

Relatively pure compounds normally melt over a narrow temperature range of ____

answer

0.5-1.5 degrees celcius

question

impure substances often melt over a much ____ range than relatively pure compounds

answer

larger

question

The presense of even small amounts of impurities can _____ the melting point a few degrees and cause melting point to ____

answer

depress; occur over a relatively wide temperature range

question

Adding greater amounts of an impurity generally causes a ____ effect on the melting point

answer

greater

question

Solid and liquid phases exist in ___ at their melting points

answer

equilibrium

question

_____ refers to a mixture of elements or compounds that has a single chemical composition, which solidifies at a lower temperature than any other composition

answer

Eutectic

question

The most common method for measuring melting points is to ____

answer

electrically heat a small amount of the solid in a capillary tube

question

The most significant advantage of a digital melting point apparatus is that you can ____

answer

program the rate at which the temperature of the heating block increases

question

both digital and analog heating devices have a _____ which normally has ____

answer

metal heating block; 3 spaces for melting point tubes

question

the temperature in a dignital melting point appparatus is measured using a ___

answer

platinum resistance sensor

question

In digital melting point apparatu you can program the ___ the ___ and the ____

answer

start temperature; temperature rmp; stop temperature

question

If temperature rises to quickly the melting range will be ____and will likely be ____ because it takesa finite amount of time for the solid sample to melt

answer

greater; higher

question

The traditional analog melting point apparatus also uses electrical heating but a ____ controls the rate of heating b alowing continuous adjustment of current

answer

rhenostate

question

The higher the rheostate setting the ____ the rate of heating

answer

faster

question

The temperature in the traditional analoge melting point apparatus is measured with a traditional ___.

answer

liquid filled thermometer

question

in the traditional analoge meltingpoint apparatus the thermometer liquid is relatively ___, thus the response time is slower than that with a digital thermometer imbedded in the metal heating block

answer

slow

question

The melting range of an organic solid can be deterined by introducing a small amount of the substance into a ___ with one ___ end

answer

capillarly tube; sealed

question

capillary tubes are approximately ___ in diameter

answer

1mm

question

filling a capillary tube. place a few ____ of the dry solid on a piece of smoother surfaced paper and ___ to a ___ by rubbing a spatula over it while pressing down.

answer

milligrams; crush; find powder

question

filling a capillary tube: introduce the solid into the capillary tube by ___. A small amount of material will stick in the open end. ____ the capillary tube so that the sealed end is down and holding it near the sealed end ____. The solid will fall to the bottom of the tube. Repeat this operation until the amount of solid in the tube is ____

answer

tapping the open end of the tube into the powder; invert; tap it lightly with quick motions against the bench top; 2-3 mm in height

question

Melting point determinations made with too much sample lead to a ____ melting range because ____

answer

broad; more time is needed to melt the complete sample, as the temperature continues to rise while the samplemelts

question

If a solid is still ___ from ___, it will not fall to the bottom of a capillary tube but will stick to the capillary wall. This is probably a good thing because melting points of ___ always have a ___ and thus are nearly worthless

answer

wet; recrystallization; wet solids; wide range

question

In melting point determination if your solid is wet you should allow it to ___ before continuing with the melting range determination

answer

dry completely

question

The accuracy of a melting point determination can be nobetter than the accuracy of the ___

answer

temperature probe

question

You cannot assume that a thermometer has been ____

answer

accuretly calibated

question

thermometers can give a high or low temperature readings of ___ or more

answer

1-2 degree celcius

question

when using digital apparatus for melting point sample can be heated rapidly until the temperature is ___ below the expected melting point. The programmed temperature ramp of ___ will then take over

answer

5-10 degrees celcius; 0.5-1.5 degrees celcius

question

_____: the onset of melting

answer

the first small drop of liquid appears

question

When using the analog melting point apparatus for melting point the melting point apparatus can be heated rapidly until the temperature is about ___ below the xpected melting point then decrease the rate of heating so that the temperature rises only ___ per minut and the sample has time to melt before the temperature rises above the true melting point

answer

20 degrees celcius; 1-2 degrees celcius

question

If you do not kknow the melting point of a solid sample you can make a quick preliminary determination of it by heating the sample ____. In a more accurate second determination you can then carfefully ___

answer

rapidly; control the temperature rise

question

Always prepare a ____ for each melting point determination because many organic compounds _____ at the melting point, making ____ a poor idea

answer

fresh; decompose; reuse of a solid sample

question

Melting range is from ___ to ___

answer

point where drop of liquid first appears to where it is all dissolved

question

Summary of melting point technique

answer

introduced the powdered, dry solid sample to a height of 2-3 mm into a capillary tube that is sealed at one end. Place the capillary tube in the melting point apparatus. adjust the rate of heating so the tempmerature rises at a moderate rate

question

How can you tell if two compounds which have virtually identical melting ranges are identical

answer

mix the two compounds together test the new melting range. If there is a melting point depression or the melting range is expanded by a number of degrees it is reasonably safe to conclude that the two compounds are not identical. If there is no change in the mixture's melting range relative to that for each separate compound, the two are probably the same compound. Test various mixture ratios to ensuure that you do not accidentally get the eutectic point

question

Only the ____ indicates the true onset of melting

answer

appearance of liquid

question

The ____ is the most important variable in determining melting ranges.

answer

rate of heating

question

2 reasons "why aren't my measured melting ranges consistant from one determination to the next"

answer

1) you are heating to fast 2) to much sample

question

____ is the change that occurs when a solid is transformed directly to a gas, without passing through the liquid phase

answer

sublimination

question

Some compounds ____ instead of melting or as they melt. This melting point is reported with the ____ after the temperature

answer

decompose; letter d

question

Gravity filtration ans suction filtration: weigh ____ of ___ on a piece of glazed paper and record the exact mass

answer

100 mg; CaCO3

question

Gravity filtration ans suction filtration:after weighing out CaCO3 transfer the solid into a _____. Measure ___ of ___ in a graduated cylinder and add to the flask

answer

Erlenmeyer flask; 5mL; acetone

question

After adding acetone to Erlenmeyer flask set up a ____ and a ____ with a ___ filter paper.

answer

filter flask; Hirsch funnel; round

question

Gravity filtration ans suction filtration: use a ___ to hold the filter flask securely

answer

clamp

question

Gravity filtration ans suction filtration: wet the filter paper with ____ from the squeeze bottle

answer

a few drops of acetone

question

Gravity filtration ans suction filtration: After attaching the flask to a vacuum source swirl the flask with suspended ___ and pour its contents onto the filter

answer

CaCO3

question

Gravity filtration ans suction filtration: What do you use to rinse the residual solid from the Erlenmeyer flask with a small amount of ____ and transfer it to the funnel. Then allow the filtered solid to ___

answer

acetone; suck dry

question

Gravity filtration ans suction filtration: disconnect the apparatus from the vacuum source, remove the ____ and carefully transfer its content to the ___. Separate the filter paper from the powder by holding the filter paper with ___ while you gently remove the solid with a spatula.

answer

funnel; glazed paper tweezers

question

What two ramps are you using for melting point

answer

1 degree celcius per minute and 10 degrees celcius per minute

question

the first capillary tube should have about ___ of compound in it while the second has ____

answer

1 millimeter; three times as much

question

what is reference m.p. for biphenyl

answer

68-70

question

what is the melting reference point for triphenylmethane

answer

92-94

question

what is the reference m.p. for acetanilide

answer

113-115

question

what is the reference m.p. for benzoic acid

answer

121-125

question

what is the reference m.p. for salicylic acid

answer

158-161

question

what is the reference melting point for 3,5 dinitrobenzoic acid

answer

204-206

question

what is the reference melting point for sucrose

answer

189-191

question

what two impure materials will be used for melting point experiment

answer

benzoic acid; acetanilide

question

boiling point acetone

answer

56 degrees celcius

question

boiling point biphenyl

answer

255

question

boiling point salicylic acid

answer

158-161

question

boiling point triphenylmethane

answer

92-94

question

boiling point acetanilide

answer

304

question

boiling point benzoic acid

answer

121-125

question

what should you keep acetone away from

answer

bases; oxidizing agents; reducing agents; phosophorus; oxychloride

question

what should you keep 3,5 dinitrobenzoic acid away from

answer

strong oxidizing agents and reducing agents, strong bases

question

what should you keep biphenyl away from

answer

strong oxidizing agents

question

what should you keep salicylic acid away from

answer

strong oxidizing agents; strong bases; iodine; iron; iron salts

question

what should we keep triphenyl methane from

answer

strong oxidizing agents

question

what should you keep acetanilide from

answer

strong oxidizing agents; strong bases

question

what should you keep benzoic acid away from

answer

strong oxidizing agents; strong bases; strong reducing agents

question

what should you keep calcium carbonate away from

answer

strong oxidizing agents; acids; magnesium; aluminum;

question

what should you keep sucrose away from

answer

strong oxidizing agents

question

3 things are dangerous with ingestion

answer

benzoic acid; acetanilide; 3,5 dinitrobenzoic acid

question

____ is very dangerous if inhaled

answer

benzoic acid

question

fire hazard 3,5 dinitrobenzoic acid

answer

2

question

fire hazard acetone

answer

3

question

health hazard acetone

answer

2

question

health hazard 3,5 dinitrobenzoic acid

answer

2

question

health hazard biphenyl

answer

3

question

fire hazard biphenyl

answer

1

question

health hazard salicylic acid

answer

2

question

health hazard acetanilide

answer

2

question

fire hazard acetanilide

answer

1

question

health hazard benzoic acid

answer

4

question

fire hazard benzoic acid

answer

1

question

health hazard calcium carbonate

answer

2

lab 2 melting point + filtration

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