Orgo 1 Lab Final

NFPA Dimond sections

blue - health
red - flammability
yellow - reactivity
white - special hazards

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

How to properly remove your gloves:

1. grasp the exterior of one glove with gloved hand
2. peel off the first glove
3. insert a bare finger between the interior edge of the second glove and the skin
4. remove the second glove

PPE protection: While pulling an empty beaker off the shelf at the beginning of lab, it slips out of your hand onto the floor.

closed-toed shoes

PPE protection: While transferring a solution from a flask to a beaker, the solution accidentally spills down the front of the lab bench.

lab coat

PPE protection: While picking up a buret, an unknown solution left by a previous solution drips onto your hand.

gloves

PPE protection: While checking on a stirring solution, the solution splashes up towards your face.

goggles

Determine when you should remove your goggles in the lab room

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

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

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

Determine when to put on disposable gloves for work in the lab

before handling any glassware or chemicals for the experiment

Determine 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

T/F: beverages are allowed in lab as long as they are in containers with lids

false

T/F: chewing gum is okay in the lab as long as you don't blow bubbles

false

T/F: food items should not be brought into the lab

true

T/F: tobacco products of all kinds are prohibited in lab

true

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

many organic materials are flammable and could cause a fire

What is the difference between a hazard and a risk?

A hazard is something that has the potential to cause harm, while a risk is a probability that that hazard will cause harm.

What is a hazard associated with water?

Hazard: Water can freeze and turn into ice, which can be hazardous on the roads while driving

What is the difference in risk between drinking water and swimming in water?

Difference: The difference is that there is more risk when swimming in water that could potentially have chemicals in it versus drinking clean/filtered

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

The risk is quite high, so goggles are worn as proper PPE to protect your eyes in case a chemical splashes up into them into the fume hood as well

How may sections are in a SDS?

16

Which section includes GHS pictograms and precautionary statements?

hazard(s) identification

Which section provides information about PPE?

exposure controls/personal protection

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

physical and chemical properties

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

first-aid measures

Briefly describe the difference between acute and chronic exposure

acute exposure is when you are in short contact with a chemical, while chronic exposure is when you are exposed to a chemical for a longer period of time. Both can cause health problems, skin irritation, etc.

How is a flammable liquid defined?

Flammable liquids are liquids that have a flash point of 100 degrees Fahrenheit or less. A flash point is the minimum temperature at which a liquid forms a vapor above its surface in sufficient concentration that it can be ignited

What is a flash point?

The flash point is the minimum temperature at which a liquid forms a vapor above its surface in a sufficient concentration that it can be ignited

What is a signal word?

Signal words include: DANGER, CAUTION, or WARNING and are used to mark toxic chemicals/pesticides to describe the short-term toxicity of an element. (DANGER = more toxic and CAUTION = less toxic).

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

An irritant chemical causes reversible inflammatory effect on living tissue by chemical site of contact, whereas a corrosive chemical tat causes visible destruction of or irreversible alterations in living tissue by chemical action at the site of contact

What are the purposes of a Safety Data Sheet?

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

When should lab participants look at the SDS of a substance?

before using the substance

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

your lab partner

What is proton NMR?

a technique that uses nuclear magnetic resonance to study the hydrogen atoms in a sample

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

Shielding can be decreased by:

the presence of more electronegative groups around the nucleus

A shielded nucleus appears:

further upfield

A deshielded nucleus appears:

further downfield

Splitting

the appearance of multiple peaks for a single nucleus due to neighboring nuclei

Chemical shift

the frequency at which a nucleus absorbs and resonates with a magnetic field

Integration

the area of a signal that corresponds to the number of nuclei at that frequency

Upfield

the end of the NMR spectrum close to the reference signal

Downfield

the end of the NMR spectrum far from the reference signal

In an NMR experiment, shielding refers to the reduced impact of the ____________ on a nucleus due to the presence of ___________ around the nucleus

1. applied magnetic field
2. electrons

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

decreased

A shielded nucleus appears further ______ whereas a deshielded nucleus appears further _______ in an NMR spectrum

1. upfield
2. downfield

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

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

In a steam bath used in Pitt Teaching Labs, which statements are true?

1. condensed steam drains out the bottom hose as water into a cup sink
2. steam enters through a hose in the top inlet of the steam bath from the steam line

After mixing the solutions in a separator 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.

1. removed
2. drained through the stopcock
3. get eye level with
4. slow the draining
5. switch to a new flask

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

1. do not mix
2. non-polar
3. polar

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

1. placing the glassware on the balance
2. press the Tare/Zero button
3. add your sample to the glassware

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

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

1. a flask under the separator funnel
2. a stopcock in the closed position
3. a funnel in the top of the separator funnel

Identify the best support for a separator funnel

iron ring clamped to a ring stand

Identify the characteristics of a good recrystallization solvent

1. dissolves a chemical sample well at high temperatures
2. does not dissolve a chemical sample well at low temperatures

Which property is the basis of the purification technique recrystallization?

solubility

Hot filtration is a type of _____ filtration in which the glassware _________. Hot filtration is useful to _________ in processes like recrystallization, in which solubility of the desired compound is dependent on _________

1. gravity
2. used at a high temperature
3. remove solid impurities
4. temperature

Which statements are true regarding a chemical mixture?

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

What are the best practices while sharing a lab balance with other students?

1. appropriately clean the balance area after use
2. alert your TA or instructor about any issues with the balance

Why do you need to support a vacuum filtration apparatus with a clamp?

1. the thick-walled vacuum tubing makes the flask tippy
2. the filter funnel makes the apparatus top-heavy

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

1. adding a small amount of water
2. slowly decant
3. into the middle of the filter paper

What should you do every time you are setting up glassware for a vacuum filtration?

1. inspect the tubing for any holes
2. ensure that the glassware is designed for use with a vacuum
3. check that there are no cracks or defects in the glassware

When using vacuum filtration to separate two solids, what techniques should you use to ensure a quantitative separation?

1. wash the solid on the filter paper with a small amount of water
2. dry the solid on the filter paper after the separation
3. wet the filter paper before pouring the mixture into the filter funnel
4. carefully rinse the flask into the filter funnel with a small amount of water

What liquid is added to the Benzoic Acid mixture in Activity 3?

diethyl ether

Why was the mixture swirled and heated upon adding the solvent in Activity 3?

to more fully dissolve the methyl orange and benzoic acid

Consider the boiling stones added to the mixture (and solvent) before heating. Which statements are true?

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

When using a separator 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

To determine the layers in a separation of organic and aqueous solutions, you ca add a small amount of _____ to the top. If the top layer is aqueous, the addition with _______ the top layer. If the bottom layer is aqueous, the addition will ______ the top layer and _______ the bottom layer.

1. water drops
2. combine with
3. travel through
4. combine with

Activity 3: Which statement(s) are true when aqueous sodium hydroxide is added to the filtrate solution (that has been transferred to the separatory funnel)?

1. an aqueous solution with a high pH was added to the funnel
2. as the benzoate ion was formed, hydroxide ion was consumed
3. benzoic acid was converted into water-soluble benzoate ions

Which property is the basis of the purification technique recrystallization?

solubility

Identify the characteristics of a good recrystallization solvent

1. dissolves a chemical sample well at high temperatures
2. does not dissolve a chemical sample well at low temperatures

In order to dissolve a chemical samples in a recrystalization 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.

1. just until it covers the sample
2. a low setting and increasing gradually
3. pipet
4. as little solvent as possible

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

Why is it necessary for the recrystallization solvent to be maintained at high temperature while dissolving the crude benzoic acid?

1. having the solvent hot allows recrystallization to occur as the solution cools as long as the solution was saturated at the hot temperature
2. a hot solvent allows for increased solute solubility
3. a hot solvent reduces crystallization during hot gravity filtration

Charcoal is often times added to a recrystallization solution that

has a colored impurity

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.

1. flute the filter paper before heating the funnel
2. use a shot-stemmed funnel in the filtration

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.

1. add a seed crystal
2. scratch the bottom of the flask gently with a stirring rod

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

1. large
2. crystals
3. slowly

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?

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

What is chromatography?

a technique to separate mixtures based on the molecular properties of the involved chemicals

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

1. Rf
2. mobile phase
3. stationary phase
4. chromatography

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 a _______. 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.

1. pencil
2. small
3. solvent
4. cover
5. solvent

What will happen if the solvent line is not marked after the TLC plate is removed from the chamber?

accurate Rf values cannot be determined

What will happen if the TLC plate remains in the chamber even after the solvent has reached the top of the plate?

accurate Rf values cannot be determined

What will happen if the mobile phase used does not move any of the spots at all?

there can be no separation of components

What will happen if pen is used rather than pencil to draw the lines on the plate?

there will be smears on the TLC plate

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

filter paper, watch glass, and beaker

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

use a UV lamp

What is the purpose of crushing the Excedrin tablet?

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

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?

1. a 50 mL beaker has a pour spout that will allow for neater transfer to the graduated cylinder
2. 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

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?

1. 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
2. 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
3. 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

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 value

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

What type of gloves were used when handling dichloromethane (DCM)?

chemically-resistant

What is the best reason for the glove choice used to handle DCM?

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

Once the ground Excedrin tablet is dissolved in DCM, why is the solution gravity-filtered?

1. to isolate the solid extract, which can then be dissolved in a different solvent and analyzed as well
2. to remove insoluble compounds like acetaminophen from the DCM extract
3. to remove binding reagents from the DCM extract

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?

Ethyl acetate extract ("EA") - aspirin, acetaminophen, and caffeine. Methanol extract ("M") - acetaminophen

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

Forgetful Fran forgot to place the cover on her developing chamber during her TLC experiment. How will this impact the development of her TLC plate?

if the cover is not placed on the developing chamber, some of the solvent could potentially escape the chamber, which could affect the composition of the mixture