OChemLab Midterm

Determine the expected number of signals in the proton NMR spectrum for benzene

1 signal

Identify the effect of this error during a thin layer chromatography experiment. The TLC plate remains in the chamber even after the solvent has reached the top of the plate.

Accurate Rf values cannot be determined

Calculate the Rf value if the solvent moved 13.8 cm and an ink component moved 6.9 cm.

0.50 Rf=distance travelled by mixture component/distance travelled by mobile phase

Identify the characteristics of a good recrystallization solvent.

-Does not dissolve a chemical sample well at low temperatures. -Dissolves a chemical sample well at high temperatures

What are purposes of the Safety Data Sheet?

-To provide a guide for the safe use of a hazardous chemical -To alert a chemist to the inherent hazards associated with a chemical

Use the Proton NMR Characteristic Table to answer the following question. What is the predicted chemical shift (ppm) range for an amino hydrogen?

0.5-5 ppm

The melting point range of a pure compound should be within what range?

1-2 degrees C

How many sections are in an SDS?

16

Determine the expected number of signals in the proton NMR spectrum for 1,1-dichloroethane

2 signals

Determine the expected number of signals in the proton NMR spectrum for 2,2-dichlorobutane

3 signals

Use the Proton NMR Characteristic Table to answer the following question. What is the predicted chemical shift (ppm) range for an aromatic hydrogen?

6.5-8 ppm

How is a flammable liquid defined and what is a flash point?

A flammable liquid is a liquid that has a flash point of less than 93 degrees C. A flash point is the lowest temperature at which a flammable liquid gives off sufficient vapor to form an ignitable mixture with air near its surface or within a vessel.

What is the difference between a hazard and a risk?

A hazard could cause a problem given the right circumstances, while a risk is the probability that a hazard will cause harm.

What is a hazard associated with water?

A person could drown in it

A shielded nucleus appears further ____ whereas a deshielded nucleus appears further ____ in an NMR spectrum.

A shield nucleus appears further UPFIELD whereas a deshielded nucleus appears further DOWNFIELD in an NMR spectrum.

What is a signal word?

A signal word is a word used to indicate the relative level of severity of hazard and alert the reader to a potential hazard on the label; 'Danger' or 'Warning' are signal words on a label.

Before adding a sample or solvent to a separatory funnel, what should you have in place?

A stopcock in the closed position, a funnel in the top of the separatory funnel, and a flask under the separatory funnel

What is chromatography?

A technique to separate mixtures based on the molecular properties of the involved chemicals. Some important molecular properties used for the separation are polarity, boiling point, and molecular size.

Identify the effect of this error during a thin layer chromatography experiment. The solvent line is not marked after the TLC plate is removed from the chamber.

Accurate Rf values cannot be calculated.

Explain the difference between acute and chronic exposure

Acute exposure is "exposure of short duration, usually to relatively high concentrations or amounts of material," while chronic exposure is "continuous or intermittent exposure extending over a long time period, usually applies to relatively low material amounts or concentrations." Therefore, the difference is the amount of time exposed and the concentrations of material.

After a recrystallization, a pure substance will ideally appear as a network of ____ ____. If this is not the case, it may be worthwhile to reheat the flask and allow the contents to cool more ____.

After a recrystallization, a pure substance will ideally appear as a network of LARGE CRYSTALS. If this is not the case, it may be worthwhile to reheat the flask and allow the contents to cool more SLOWLY.

What is the difference between an irritant and a corrosive chemical?

An irritant is a chemical that causes a reversible inflammatory effect on living tissue by chemical action at the site of contact, while a corrosive chemical is a chemical that causes visible destruction of or irreversible alterations in living tissue by chemical action at the site of contact, or that causes a severe corrosion rate in steel or aluminum. Therefore, the difference between them is that an irritant causes reversible effects, while a corrosive chemical causes irreversible effects.

Why should Bunsen burners not be used when heating organic materials?

Because many organic materials are flammable and could cause a fire

Benzoin and Maleic Acid have the same melting point (136-137 °C). Your TA gave you an unknown compound that has a melting point of 136-137 °C. You added a small amount of pure benzoin to your unknown compound and the melting point of the mixture was 136-137 °C. You added a small amount of maleic acid to your unknown compound and the melting point of the mixture was 124-129 °C. What is the unknown compound likely to be?

Benzoin

Changing gloves often will minimize the spread of chemicals. To properly remove gloves, first, _________, and then _______. Then insert ______ between the interior edge of the second glove and the skin, and remove the second glove.

Changing gloves often will minimize the spread of chemicals. To properly remove gloves, first, GRASP THE EXTERIOR OF ONE GLOVE WITH A GLOVED HAND, and then PEEL OFF THE FIRST GLOVE. Then insert A BARE FINGER between the interior edge of the second glove and the skin, and remove the second glove.

The frequency at which a nucleus absorbs and resonates with a magnetic field is called this

Chemical shift

While pulling an empty beaker off the shelf at the beginning of lab, it slips out of your hand onto the floor. What item of PPE will protect you from this incident?

Closed-Toe Shoes

What is the best reason for the glove choice used to handle DCM during the Solid-Liquid Extraction (Tablet-DCM)?

DCM more quickly breaks through nitrile and latex gloves than it breaks through chemically-resistant gloves.

The end of the NMR spectrum far from the reference signal is called this

Downfield

What section of the SDS provides information about PPE?

Exposure Controls/Personal Protection

What is the best course of action if solid material remains in the flask after the heating step of a recrystallization?

Filter the hot mixture

Which section gives advice about how to respond if a person is exposed to a chemical?

First-aid Measures

While picking up a buret, an unknown solution left by a previous solution drips onto your hand. What item of PPE will protect you from this incident?

Gloves

While checking on a stirring solution, the solution splashes up towards your face. What item of PPE will protect you from this incident?

Goggles

For the following molecules, rank the polarity from most to least polar. CH2Cl2, CH3OH, H2O

H20 > CH3OH > CH2Cl2

Which section of an SDS includes GHS pictograms and precautionary statements?

Hazard(s) Identification section

Water and hexanes (C6H14) are mixed together in a separatory funnel. Which compound will be the top layer in the funnel?

Hexanes

Hot filtration is a type of ____ filtration in which the glassware is _____.

Hot filtration is a type of GRAVITY filtration in which the glassware is USED AT A HIGH TEMPERATURE.

Hot filtration is useful to ____ in processes like recrystallization, in which solubility of the desired compound is dependent on ____.

Hot filtration is useful to REMOVE SOLID IMPURITIES in processes like recrystallization, in which solubility of the desired compound is dependent on TEMPERATURE.

In an NMR experiment, shielding refers to the reduced impact of the ____ on a nucleus due to the presence of _____ around the nucleus.

In an NMR experiment, shielding refers to the reduced impact of the APPLIED MAGNETIC FIELD on a nucleus due to the presence of ELECTRONS around the nucleus

In general, when hydrocarbons like oil are added to water, the two liquids ____ because hydrocarbons are ____ and water is ____.

In general, when hydrocarbons like oil are added to water, the two liquids DO NOT MIX because hydrocarbons are NON-POLAR and water is POLAR.

In order to dissolve a chemical sample in a recrystallization solvent, add the room-temperature solvent ____ in an Erlenmeyer flask on a hot plate. Turn on the heat, starting at ____. Using a ____, add additional solvent from a second container on the heat source. Swirl the sample flask after each addition, and try to add ____ in order to dissolve the solid.

In order to dissolve a chemical sample in a recrystallization solvent, add the room-temperature solvent JUST UNTIL IT COVERS THE SAMPLE in an Erlenmeyer flask on a hot plate. Turn on the heat, starting at A LOW SETTING AND INCREASING GRADUALLY. Using a PIPET, add additional solvent from a second container on the heat source. Swirl the sample flask after each addition, and try to add AS LITTLE SOLVENT AS POSSIBLE in order to dissolve the solid.

The area of a signal that corresponds to the number of nuclei at that frequency is called this

Integration

Identify the best support for a separatory funnel.

Iron ring clamped to a ring stand

While transferring a solution from a flask to a beaker, the solution accidentally spills down the front of the lab bench. What item of PPE will protect you from this incident?

Lab Coat

Note: Acetaminophen is partially soluble in ethyl acetate; aspirin and caffeine are soluble in ethyl acetate. Suppose that the solid-liquid extraction in Part 2 of this experiment is performed using ethyl acetate instead of DCM. The resulting ethyl acetate liquid extract is labelled "EA" and the insoluble components of ethyl acetate extraction are dissolved in methanol, "M". What would you expect to see in a developed TLC plate of the "EA" extract? What would you expect to see in a developed TLC plate of the "M" extract?

Methanol Extract ("M"): Acetaminophen Ethyl Acetate Extract ("EA"): Aspirin, Acetaminophen, and Caffeine

Are beverages allowed in lab as long as they are in containers with lids?

No

Is chewing gum okay in the lab as long as you don't blow bubbles?

No

Once the vacuum filtration set-up is complete, start by ____ in the filter funnel. Then, ____ the mixture ____.

Once the vacuum filtration set-up is complete, start by ADDING A SMALL AMOUNT OF WATER in the filter funnel. Then, SLOWLY DECANT the mixture INTO THE MIDDLE OF THE FILTER PAPER.

When using a separatory funnel, you should vent the funnel. What does the term venting mean?

Opening the stopcock to relieve pressure build-up within the funnel while inverted

When should you remove your goggles in the lab room?

When everyone in the room is done handling any chemicals or glassware

Which section provides physical property data such as melting and boiling points?

Physical and Chemical Properties

The hazards associated with this pictogram is explosives, self-reactive, organic peroxides

Pictogram includes a bomb exploding

The hazards associated with this pictogram is flammables, pyrophorics, self-heating, emits flammable gas, self-reactives, organic peroxides

Pictogram includes a fire

The hazards associated with this pictogram is gases under pressure

Pictogram includes a rectangular object

The hazards associated with this pictogram is acute toxicity (fatal or toxic)

Pictogram includes a skull with bones

The hazards associated with this pictogram is irritant (skin and eye), skin sensitizer, acute toxicity, narcotic effects, respiratory tract irritant

Pictogram includes an exclamation point

The hazards associated with this pictogram is skin corrosions, burns, eye damage, corrosive to metals

Pictogram includes chemicals spilling from test tubes onto a hand and metal

The hazards associated with this pictogram is oxidizer

Pictogram includes fire above a circle

The hazards associated with this pictogram is carcinogen, mutagenicity, reproductive toxicity, respiratory sensitizer, target organ toxicity, aspiration toxicity

Pictogram includes the upper half of human with an outburst on its chest

Proton NMR is a technique that uses ____ to study the ____ in a sample

Proton NMR is a technique that uses NUCLEAR MAGNETIC RESONANCE to study the HYDROGEN ATOMS in a sample

Recrystallization requires dissolving an impure compound in ____ so that ____.

Recrystallization requires dissolving an impure compound in HOT SOLVENT so that BOTH THE DESIRED PRODUCT AND THE IMPURITIES DISSOLVE.

Identify the significance of each section on the NFPA Diamond Red, Blue, Yellow, White

Red= Flammability Blue= Health Yellow= Reactivity White= Special Hazards

What should you do every time before you leave the lab?

Remove your gloves, remove your lab coat, if you are wearing one, and wash your hands

Your goal is to separate two solids by adding water and then filtering the mixture. What are the final steps of ending up with two separate solids? Assume only one of the solids is water soluble.

Scrape the solid off the filter paper into one container and evaporate the water from the filtrate to isolate the other solid.

Shielding can be _____ by the presence of more electronegative groups around the nucleus.

Shielding can be DECREASED by the presence of more electronegative groups around the nucleus.

From the perspective of synthetic chemists, what potential disadvantage do steam baths have compared to hot plates for heating?

Some reactions, like Grignard reactions, are water sensitive.

The appearance of multiple peaks for a single nucleus due to neighboring nuclei is called this

Splitting

Why are steam baths considered a safer way to heat organic liquids than hot plates?

The risk of fire when working with flammable solvents is reduced

What would happen if too much analgesic/analyte was spotted on a TLC plate?

The spot would streak up the plate, making it very difficult to calculate an accurate Rf

The substance that carries the components of a mixture ____. A value that quantifies the distance traveled by a substance relative to the distance traveled by the solvent ____. The substance to which the sample is bound at the start of an experiment ____. A method used to separate components of a mixture ____.

The substance that carries the components of a mixture MOBILE PHASE. A value that quantifies the distance traveled by a substance relative to the distance traveled by the solvent RF. The substance to which the sample is bound at the start of an experiment STATIONARY PHASE. A method used to separate components of a mixture CHROMATOGRAPHY.

Identify the effect of this error during a thin layer chromatography experiment. Pen rather than pencil is used to draw the lines on the plate.

There will be smears on the TLC plate

To determine the layers in a separation of organic and aqueous solutions, you can add a small amount of ____ to the top. If the top layer is aqueous, the addition will ____ to the top layer. If the bottom layer is aqueous, the addition will ____ the top layer and ____ the bottom layer.

To determine the layers in a separation of organic and aqueous solutions, you can add a small amount of WATER DROPS to the top. If the top layer is aqueous, the addition will COMBINE WITH the top layer. If the bottom layer is aqueous, the addition will TRAVEL THROUGH the top layer and COMBINE WITH the bottom layer.

To run a thin layer chromatography experiment with a chemical substance, begin by marking a horizontal line near the bottom of a TLC plate with ____. Place a ____ spot of the substance onto the line. For the mobile phase, add a small amount of ____ at the bottom of a TLC chamber. Place the plate in, then ____ the chamber. Once the mobile phase approaches the top of the plate, remove the plate and mark the ____ line. Note the position of the spots and calculate Rf values if needed.

To run a thin layer chromatography experiment with a chemical substance, begin by marking a horizontal line near the bottom of a TLC plate with PENCIL. Place a SMALL spot of the substance onto the line. For the mobile phase, add a small amount of SOLVENT at the bottom of a TLC chamber. Place the plate in, then COVER the chamber. Once the mobile phase approaches the top of the plate, remove the plate and mark the SOLVENT line. Note the position of the spots and calculate Rf values if needed.

What is the purpose of preparing three different TLC chambers?

To test three different solvent systems for the mobile phase that gives the best separation

True or False: A nonpolar molecule like hexane has very little or no difference in electronegativity between its bonded atoms and no net dipole.

True

The end of the NMR spectrum close to the reference signal is called this

Upfield

In lab, you may need to evaluate the odor or smell of a chemical. What is the best way to smell a chemical sample?

Use your hand to gently waft the smell toward you

What is the safest option in the lab if you need your vision to be corrected?

Wear corrective glasses or lenses under your safety goggles for the whole experiment, but always check with your TA or Instructor for your school's policy

When using the Tare function on a balance, start by ____. Then, ____ to cancel out that mass. Finally, ____ and record the mass of your sample.

When using the Tare function on a balance, start by PLACING THE GLASSWARE ON THE BALANCE. Then, PRESS THE TARE/ZERO BUTTON to cancel out that mass. Finally, ADD YOUR SAMPLE TO THE GLASSWARE and record the mass of your sample.

Hot filtration is a technique in which the mixture is heated and all the glassware is also heated for the filtration. When should you use the technique of hot filtration?

When you are separating a slightly soluble solid from an insoluble solid

While performing extraction: After mixing the solutions in a separatory funnel, the stopper should be ____ and the liquid should be ____ and the layers allowed to separate. When you get close to the interface between the layers, ____ the funnel and ____ until the first layer is collected. ____ to collect the second layer.

While performing extraction: After mixing the solutions in a separatory funnel, the stopper should be REMOVED and the liquid should be DRAINED THROUGH THE STOPCOCK and the layers allowed to separate. When you get close to the interface between the layers, GET EYE LEVEL WITH the funnel and SLOW THE DRAINING until the first layer is collected. SWITCH TO A NEW FLASK to collect the second layer.

Are tobacco products of all kinds prohibited in lab?

Yes

Should food items not be brought into the lab?

Yes

Melting point is an example of ____

a physical change

Which statements below are true regarding a chemical mixture? Select all that apply. a. A material made up of two or more substances in which their identities are maintained. b. A chemical mixture can be homogeneous or heterogeneous c. A mixture can never be separated by physical means d. Any substance made up of two or more elements. e. A mixture can only be separated by chemical means.

a. A material made up of two or more substances in which their identities are maintained. and b. A chemical mixture can be homogeneous or heterogeneous

During the Recrystallization of Benzoic Acid, If crystal growth does not start on its own after the solution in the flask returns to room temperature, identify the best ways to promote crystal growth. Select one or more: a. Add a seed crystal. b. Place the flask on a hot plate to evaporate some solvent. c. Add ice cubes to the solution. d. Scratch the bottom of the flask gently with a stirring rod.

a. Add a seed crystal and d. Scratch the bottom of the flask gently with a stirring rod

Which statement(s) are true when aqueous sodium hydroxide is added to the filtrate solution (that has been transferred to the separatory funnel) during Chemically Active Extraction of Benzoic Acid? Select all that apply. a. Benzoic acid was converted into water-soluble benzoate ions. b. As the benzoate ion was formed, hydroxide ion was consumed. c. An aqueous solution with a low pH was added to the filtrate. d. An aqueous solution with a high pH was added to the funnel. e. Hydroxide ions protonated benzoic acid molecules. f. Immiscible liquids are now present in the separatory funnel

a. Benzoic acid was converted into water-soluble benzoate ions. b. As the benzoate ion was formed, hydroxide ion was consumed. d. An aqueous solution with a high pH was added to the funnel. and f. Immiscible liquids are now present in the separatory funnel

When using vacuum filtration to separate two solids, what techniques should you use to ensure a quantitative separation? Note: Assume this theoretical separation is done using water. Select all that apply. a. Carefully rinse the flask into the filter funnel with a small amount of water b. Wet the filter paper before pouring the mixture into the filter funnel c. Wash the solid on the filter paper with a small amount of water d. Dry the solid on the filter paper after the separation

a. Carefully rinse the flask into the filter funnel with a small amount of water b. Wet the filter paper before pouring the mixture into the filter funnel c. Wash the solid on the filter paper with a small amount of water and d. Dry the solid on the filter paper after the separation Explanation: To ensure quantitative separation, you need to make sure that all the solid is caught on the filter paper and that all the solute makes it through the filter paper to the filtrate. The first important step is to wet the filter paper before pouring the mixture into the filter funnel. This will make sure that the filter paper adheres to the filter funnel so that no solid makes it under the filter paper to the filtrate. Then, after decanting the mixture into the filter funnel, rinse the flask containing the mixture into the filter funnel. The rinse makes sure that none of the mixture gets left behind in the original flask. Next, rinse the solid on the filter paper to make sure that no solute remains in the wet solid on the filter paper. Finally, leave the solid on the filter paper for a while to make sure that all the liquid is pulled into the filtrate and that the solid is thoroughly dry.

What should you do every time you are setting up glassware for a vacuum filtration? Select all that apply. a. Check that there are no cracks or defects in the glassware. b. Inspect the tubing for any holes c. Dry the outside of all the glassware. d. Ensure that the glassware is designed for use with a vacuum

a. Check that there are no cracks or defects in the glassware. b. Inspect the tubing for any holes and d. Ensure that the glassware is designed for use with a vacuum

Why is it necessary for the recrystallization solvent to be maintained at high temperature while dissolving the crude benzoic acid while Prepping for Recrystallization? Select all that apply. a. Having the solvent hot allows recrystallization to occur as the solution cools as long as the solution was saturated at the hot temperature. b. A hot solvent prevents saturation c. A hot solvent reduces crystallization during hot gravity filtration d. A hot solvent allows the benzoic acid to melt e. A hot solvent lowers the kinetic energy of the molecules, helping them remain calm without medication f. A hot solvent allows for increased solute solubility

a. Having the solvent hot allows recrystallization to occur as the solution cools as long as the solution was saturated at the hot temperature. c. A hot solvent reduces crystallization during hot gravity filtration and f. A hot solvent allows for increased solute solubility

While Preparing Analgesic TLC Standard, why does the chemist transfer methanol from the 4 L bottle into the 50 mL beaker and then from the 50 mL beaker into the graduated cylinder rather than transferring methanol directly from the 4 L bottle into the graduated cylinder? Select all that apply. a. It is safer to pour into an intermediate container that has a larger mouth so that methanol is less likely to spill when filling the 10 mL graduated cylinder. b. The chemist should have directly transferred from the 4 L container, they just made a technique error. c. A 50 mL beaker has a pour spout that will allow for neater transfer to the graduated cylinder d. It is better to use as much glassware as possible to prevent cross-contamination of chemicals.

a. It is safer to pour into an intermediate container that has a larger mouth so that methanol is less likely to spill when filling the 10 mL graduated cylinder. and c. A 50 mL beaker has a pour spout that will allow for neater transfer to the graduated cylinder

In a steam bath used in Pitt Teaching Labs, which statements are true? Select all that apply. a. Steam enters through a hose in the top inlet of the steam bath from the steam line. b. Condensed steam drains out the bottom hose as water into a cup sink c. Steam is generated by boiling water inside the bath.

a. Steam enters through a hose in the top inlet of the steam bath from the steam line. and b. Condensed steam drains out the bottom hose as water into a cup sink

While Prepping Eluent Chambers and TLC Plates, why does the chemist carefully trace a baseline with a pencil straight across the plate at least 1-2 cm from the bottom of the plate? Check all that are true. a. The baseline must be above the solvent level in the TLC chamber so that the baseline spots do not dissolve into the mobile phase at the bottom of the chamber. b. The baseline needs to be the same distance from the bottom of the plate for all of the spots in order to calculate accurate Rf. c. The baseline does not need to be straight; the mobile phase will move the spots along the stationary phase regardless of where the baseline starts. You can spot wherever you want. d. A pencil is used instead of a pen because a pen will result in ink streaking across the plate, making analysis of the plate difficult or impossible.

a. The baseline must be above the solvent level in the TLC chamber so that the baseline spots do not dissolve into the mobile phase at the bottom of the chamber. b. The baseline needs to be the same distance from the bottom of the plate for all of the spots in order to calculate accurate Rf. and d. A pencil is used instead of a pen because a pen will result in ink streaking across the plate, making analysis of the plate difficult or impossible.

Consider the boiling stones added to the mixture (and solvent) before heating during Solid Liquid Extraction and Filtration. Which statements are true? Select all that apply. a. The ether-insoluble cellulose could have served the role (prevent bumping) of the boiling stones b. It is good practice to be in the habit of adding boiling stones to all liquids that are going to be heated in the laboratory. c. The boiling stones lower the boiling point of ether. d. The boiling stones prevent hot pockets of vapor from building up in the heated solvent, which if left unchecked, can lead to violent bumping, splashes, and boil overs.

a. The ether-insoluble cellulose could have served the role (prevent bumping) of the boiling stones b. It is good practice to be in the habit of adding boiling stones to all liquids that are going to be heated in the laboratory. and d. The boiling stones prevent hot pockets of vapor from building up in the heated solvent, which if left unchecked, can lead to violent bumping, splashes, and boil overs.

Once the ground Excedrin tablet is dissolved in DCM during the Solid-Liquid Extraction (Tablet-DCM), why is the solution gravity-filtered? Check all that apply. a. To remove insoluble compounds like acetaminophen from the dichloromethane extract b. To remove binding reagents from the dichloromethane extract c. To isolate the solid extract, which can then be dissolved in a different solvent and analyzed as well d. To remove aspirin and caffeine contaminants from the dichloromethane extract

a. To remove insoluble compounds like acetaminophen from the dichloromethane extract b. To remove binding reagents from the dichloromethane extract and c. To isolate the solid extract, which can then be dissolved in a different solvent and analyzed as well

Use the Proton NMR Characteristic Table to answer the following question. What is the predicted chemical shift (ppm) range for a tertiary alkyl hydrogen?

around 1.5 ppm

What are the best practices while sharing a lab balance with other students? Select one or more: a. Place samples directly onto the balance. b. Alert your TA or instructor about any issues with the balance c. Appropriately clean the balance area after use d. Leave a note when you have tared a balance for your glassware.

b. Alert your TA or instructor about any issues with the balance and c. Appropriately clean the balance area after use

While Prepping for Recrystallization, a hot filtration needs to be performed quickly to avoid crystallization in the glassware. Identify the appropriate practices you can use to prevent unwanted crystallization. Select one or more: a. Add a stir bar to the filter paper to stir the sample. b. Use a short-stemmed funnel in the filtration. c. Flute the filter paper before heating the funnel. d. Evaporate some solvent from the sample before filtering.

b. Use a short-stemmed funnel in the filtration. and c. Flute the filter paper before heating the funnel.

How is the risk of an eye injury when working with chemicals controlled in the laboratory?

by wearing goggles

When should you put on disposable gloves for work in the lab? a. Before entering the laboratory room b. After cleaning all the glassware for the experiment c. Before handling any glassware or chemicals for the experiment d. After setting up all the glassware but before handling chemicals

c. Before handling any glassware or chemicals for the experiment

What happened as aqueous hydrochloric acid was added to the combined aqueous layers that were drained out of the separatory funnel while Recovering Separated Benzoic acid? Select one or more. a. The solution became pink because benzoic acid is pink at low pH. b. Benzoate ion became less water soluble. c. Hydrochloric acid reacted with the benzoate ion to make benzoic acid. d. Benzoic acid precipitated out of the aqueous solution. e. Hydrochloric acid reacted with hydroxide ion to make water.

c. Hydrochloric acid reacted with the benzoate ion to make benzoic acid. d. Benzoic acid precipitated out of the aqueous solution. and e. Hydrochloric acid reacted with hydroxide ion to make water.

What type of information can be found in the Identification section of the SDS?

chemical name and formula

What type of gloves were used when handling dichloromethane (DCM) during the Solid-Liquid Extraction (Tablet-DCM)?

chemically-resistant

Why do you need to support a vacuum filtration apparatus with a clamp? Select all that apply. a. The filter funnel is held in place by the clamp. b. The side-arm flask does not work without a clamp. c. The side-arm flask cannot sit directly on the benchtop. d. The filter funnel makes the apparatus top-heavy e. The thick-walled vacuum tubing makes the flask tippy.

d. The filter funnel makes the apparatus top-heavy and e. The thick-walled vacuum tubing makes the flask tippy.

True or False: To obtain pure crystals, the crystal lattice structure should contain molecules of various types.

false

Charcoal is often times added to a recrystallization solution that:

has a colored impurity

What information is necessary to review in order to be considered familiar with the Safety Data Sheet (SDS) of a substance?

identification and description of substance, hazard warnings, personal protection and first aid recommendations, and handling, storage, and reactivity information

What type of information can be found in the Handling and Storage section of the Safety Data Sheet?

incompatibility or reactivity with other chemicals

What type of information can be found in the Hazards Identification section of the Safety Data Sheet?

possible dangers and health effects

What type of information can be found in the First-aid Measures section of the Safety Data Sheet?

recommendations in case of accidental contact with the chemical

What type of information can be found in the Exposure Controls/Personal Protection section of the SDS?

recommended personal protective equipment (PPE)

Why is it a good idea to use UV light to visualize the undeveloped TLC plate before developing it in the TLC chamber?

so you can tell if your spots are too big or too small and make another TLC plate if needed

Which property is the basis of the purification technique recrystallization?

solubility

What types of chemicals are hazardous?

strong acids, weak acids, strong bases, weak bases, water, inorganic salts, corrosive chemicals, strong oxidizers, flammable materials, pryophorics, highly toxic chemicals, irritants, organic solvents, explosives, and poisons

Suppose you are performing an extraction procedure with a carboxylic acid, like a benzoic or toluic acid. Which layer should contain the carboxylic acid in a two-layer mixture of water and an organic solvent, like diethyl ether? You then add a base to form the corresponding carboxylate. Which layer should contain the carboxylate in a two-layer mixture of water and an organic solvent, like diethyl ether?

the organic layer, then the aqueous layer

Identify the effect of this error during a thin layer chromatography experiment. The mobile phase used does not move any of the spots at all.

there can be no separation of components.

What is the purpose of crushing the Excedrin tablet while Preparing Analgesic TLC Standard?

to make it easier for the Excedrin components to dissolve in solution

What is the best listed approach for viewing spots that are not visible on a TLC plate?

use a UV lamp

Suppose you are going to perform a TLC experiment, which materials will you use to prepare the TLC development chamber?

watch glass, filter paper, and a beaker

What is NOT a good source of information about the hazards that affect waste disposal in a chemistry lab?

your lab partner