Quiz Questions Flashcards
Which of the following factors determines whether a solute will dissolve in a solvent?
molecular dipoles, molecular geometry, intermolecular forces, electrostatic attraction
What are the strongest intermolecular forces that must be overcome when melting menthol?
hydrogen bonding
steps for using a digital balance in the correct order
- Determine the container to weigh chemicals into: small beaker, weighing paper, or weighing boat
- Place the weighing container on the balance pan and press “Tare” or “Zero”
- Use a spatula to transfer solid chemical into the container
- Close the draft shields and record the mass once the reading has stabilized
- Use a brush or paper towel to clean up spills in and around the balance
WHat effect do impurities or solutes have on the melting point of a substance?
impurities lower the melting point
when impurities lower the melting point what is the colligative property called
freezing point depression
A solution is created when a small amount of ______ dissolves in a larger amount of _______. When a solutions concentration is reported in moles of _____ per liter of solution, the concentration is reported as a _____. When a solution’s concentration is reported in moles of ____ per _____ of solvent, the concentration is reported as a _______
solute, solvent, solute, molarity, solute, kilogram, molality
molality equation
moles of solute/ kg of solvent
what is the freezing point depression constant folrmula
Tf(solvent)- Tf(solution)= Kf x molality
The most probable laboratory emergencies are chemical spills, minor burns and cuts, and fires. Which of the following statements are TRUE about responding to emergencies?
If possible turn off lab equipment before leaving lab for a fire alarm
Stay calm
Know where the stairwells are
All laboratories must have two exits
ALL ARE TRUE
Which of the following statements are true
Cinnamic Acid dissolves into melted menthol
Cinnamic acid does not stay dissolved in solid menthol
Cinnamic Acid solidifies when menthol freezes
Menthol dissolves when heated
None of these
Cinnamic Acid dissolves into melted menthol
Cinnamic acid does not stay dissolved in solid menthol
how to determine the molar mass of the unknown
Temp f (solvent)- Tempf(solution)= kf x ((mass of unknown/molar mass of unknown)/ kg of solvent)
Because the three possible unknowns (cinnamic acid, vanillin and 4-hydroxybenzaldehyde) have either carboxylic acid or phenol functional groups, they are all weak acids.
How will this weak acidity affect the freezing point depression?
the solution freezing point is lower than it should be
Because the three possible unknowns (cinnamic acid, vanillin and 4-hydroxybenzaldehyde) have either carboxylic acid or phenol functional groups, they are all weak acids.
What is the source of this effect?
more particles are in solution because of dissociation
Because the three possible unknowns (cinnamic acid, vanillin and 4-hydroxybenzaldehyde) have either carboxylic acid or phenol functional groups, they are all weak acids.
How will the calculated molecular mass differ from the actual value?
The calculated molecular mass is lower
Open Odyssey, go to the Miscellaneous tab, find the Solutions section and click on M I2 Molarity vs Molality. Follow the instructions on the screen and click on all the available buttons.
Why is molality used instead of molarity in this project?
Volume changes with temperature
Open Odyssey, go to the Miscellaneous tab, find the Solutions section and click on M I2 Molarity vs Molality. Follow the instructions on the screen and click on all the available buttons.
Under what conditions are the values of molarity and molality very different?
high concentrations
Open Odyssey, go to the Miscellaneous tab, find the Solutions section and click on M I2 Molarity vs Molality. Follow the instructions on the screen and click on all the available buttons.
Which value is higher?
molality
Which of the following common household products contain flammable chemicals?
gasoline, rubbing alcohol, nail polish remover, antifreeze
which of the following are ways to stop a fire?
remove ignition sources, place a beaker over a small flame to remove oxygen, ground metal container to prevent static electricity, limit quantities of flammable substances in work area
Which of the following statements are true about flammability?
Inflammable is another word for flammable
A fire cannot start above or below a vapor’s flammability limits
The National Fire Protection Association (NFPA) diamond has a [A] section for flammability. If the number [B] appears in this section, the chemical is extremely flammable. If the number [C] appears in this section, the chemical is a combustible, it will catch fire when heated. The Global Harmonized System (GHS) symbol is a picture of a [D]. If the hazard category is [E], the chemical is extremely flammable. If the hazard category is [F], the chemical is combustible.
red, 4, 2, fire, HC1,HC4
A mixture of acetone and heptane is used in this project to create the TLC eluent. Only a small amount of liquid
(2−3mL)is needed for the development chamber, so the volume to volume ratios of heptane to acetone must be converted to reasonable quantities so that excess waste is not created. If the total volume is 2−3mL fill in the table to show how much of each chemical is needed to make the ratio.
Heptane : Acetone Ratio of 1:1
Heptane : Acetone Ratio of 1:2
Heptane : Acetone Ratio of 2:1
Heptane : Acetone Ratio of 3:2
1 mL Heptane : 1mL Acetone
1 mL Heptane : 2mL Acetone
2 mL Heptane : 1mL Acetone
1.5 mL Heptane : 1mL Acetone
A mixture of acetone and heptane is used in this project to create the TLC eluent. Only a small amount of liquid
(2−3mL)is needed for the development chamber, so the volume to volume ratios of heptane to acetone must be converted to reasonable quantities so that excess waste is not created. If the total volume is 2−3mL fill in the table to show how much of each chemical is needed to make the ratio.
The ratio between the solvents should be reasonably precise, but not as precise as when making standard solutions for a Beer’s Law plot. What is the best piece of glassware to measure out the above volumes?
graduated cylinder
Order the steps for preparing and developing a TLC plate.
- With a pencil, draw a baseline
- Use a capillary to deliver 1-2 drops of concentrated analyte solution
- Allow the analyte spots to dry
- Place plate in TLC chamber so that it doesnt touch the filter paper
- Cap TLC chamber
- Remove plate before solvent front reaches the top of the plate
- Mark the solvent front
- Measure distances to calculate Rf values
when looking at a TLC which compound is more polar?
the compound that moves the least
which compound is most attracted to the eluent
the compound that moves the most/ is closest to the solvent front
Match the TLC issue with the cause.
All the analyte spots are in the upper region of the TLC plate & close together
the eluent was too polar
Match the TLC issue with the cause.
Analyte spots moved up the plate diagonally instead of vertically
The TLC plate was touching the filter paper wick
Match the TLC issue with the cause.
While spotting the analyte spot became too large
The TLC plate was not allowed to dry between drops
Match the TLC issue with the cause.
Rf values differ for 2 identically spotted plates from the same developing chamber containing 2:1 acetone:heptane eluent
The developing chamber is not capped resulting in evaporation
Which of the following are true statements about fume hoods? (Select all that apply)
the window on the front of the fume hood is called a sash
a tissue paper held at the bottom of a sash should blow into the hood
All work should be done at least 6 inches inside the hood
room air should be drawn into the fume hood
PEL?
permissible exposure limit
odor threshold
gas concentration that 50% of the population can detect
odor fatigue
decreased sensitivity to odor over time
IDLH?
immediate dangerous to life and health
OEL?
occupational exposure limits
How can you tell if a chemical is hazardous after you smell it? Which of these chemicals will you smell after it becomes hazardous?
basically PEL has to be lower than odor threshold
hexane: 50 ppm (PEL), 130 ppm(odor threshold)
dichloromethane: 25ppm (PEL), 130 ppm(odor threshold)
methanol: 200ppm (PEL), 5900ppm (odor threshold)
what is the major underlying principle of chromatography?
separation will be achieved if one component adheres to the stationary phase more than the other component does
A student dissolved a product in acetone and spotted on a silica TLC plate to determine the purity of the product. A 2:1 mixture of heptane:acetone was placed in the developing chamber.
a) In this setup, silica is the:
stationary phase
A student dissolved a product in acetone and spotted on a silica TLC plate to determine the purity of the product. A 2:1 mixture of heptane:acetone was placed in the developing chamber.
b) The heptane/acetone mixture is the: (select all that apply)
mobile phase
eluent
you have a tlc where the standard C does move from the baseline
why didn’t C move from the baseline
C is strongly absorbed to the silica bc of its polarity
which of the following statements are true about the permanganate?
most of the plate turns pink because unreacted permanganate is pink
if a compound has a double binds its TLC spots turn yellow
Odyssey data:
Carvone dipole moment is 4.1
Dihydrocarveol dipole 2.1
Limonene: 0.2
Which compound will travel the furthest up the TLC plate?
limonene bc its the most nonpolar
The compound that travels the furthest up the TLC plate will have the ________ Rf Value
largest
Odyssey data:
Carvone dipole moment is 4.1
Dihydrocarveol dipole 2.1
Limonene: 0.2
c) View the electrostatic potential maps of each molecule by clicking on the
icon. Which molecule has the least amount of red and blue coloring?
limonene- bc its most nonpolar aka least polar
Odyssey data:
Carvone dipole moment is 4.1
Dihydrocarveol dipole 2.1
Limonene: 0.2
Do the dipoles in Odyssey correctly predict the Rf values of the other two compounds?
No, dihydrocarveol’s dipole should be larger
which statement about gloves is true?
no glove material protects against all chemicals
gloves should be removed when they come into contact with any hazardous chemicals
permeation
ability of a chemical to penetrate the glove material through small pores
degradation
destructive change in the glove material
breakthrough time
time for the first appearance of a chemical on the other side of the glove
rate of transfer
speed at which a chemical appears on the other side of the glove
which of the following are true about lab coats
sleeves should never be rolled up
Lab coats should never be worn outside of lab
nitrile gloves are used in general and organic chemistry laboratory. which of the following statements are TRUE about nitrile gloves
nitrile gloves protect well against an aliphatic hydrocarbons like heptane and limonene
Which of the following guidlines should be followed to protect your skin in the chemistry laboratory
use gloves when appropriate to do so
wear clothing that covers most of your body
wear a lab coat
wear sturdy closed toed and heel shoes
Order the steps if vacuum( or suction) filtration
- place thr Buchner funnel in a sied arm filter flask and attach the filter fask to the hose coming from the vacuum
- place the unfolded circular filter paper into the funnel and wet it with solvent
- open the vacuum valve on the fume hood or turn on the vacuum aspirator
- pour mixture into the funnel
- use a spatula to transfer solids to the funnel
- Rinse beaker that contained the mixture and spatula three times, add rinsings to the funnel
- close vacuum valve or turn off water aspirator before removing hose from the side arm flask
Place the steps listed below for using a Digi-Melt in Order
- Turn on the Digi-Melt
- Set starting temperature
- Set the stop temperature
- set the rate at which temperature should ramp up
- add solid to capillary tube
- Tap solid to bottom of capillary tube
- place filled capillary into top slots
- Press start/stop to start heating
- Watch sample for melting through eye piece
- record melting range
- press start/stop to end heating
Order the steps listed below in the proper order for taking an absorbance spectrum
- prepare a blank by filling a cuvette with solvent
- wipe outside of blank cuvette with tissue
- calibrate spectrometer with blank
- pre-rinse cuvette with a small portion of solution
- fill cuvette with solution
- wipe outside of solution cuvette with tissue
- place cuvette in spectrometer, push play and then stop
- dilute initial solution if absorbance is too high pr top of spectra is ragged or flatlines at the top. Repeat procedure
- Attach file to ELN
acute toxicity
ability of a chemical to do damage with a single dose
chronic toxicity
ability of a chemical to do damage after multiple doses
LC 50
lethal concentration that 50% of a population dies
LD50
lethal dose that kills 50% of a population
toxicant
chemical producing toxic effects
toxicity
ability of a chemical to damage an organ
toxicology
study adverse effects of chemicals
toxin
toxic substance made by plant, animal, fungi or bacterium
Which of the following statements are TRUE about the factors influencing toxicity?
animal models may not be a good representation of human response
the dose makes the poison
the very young and old are most susceptible to toxic effects
Acetaminophen (tylenol) fate in the human body
metabolized and removed by the liver
DDT fate in the human body
bioaccumulation- stored in fat
Ethylene glycol fate in the body
metabolized to calcium oxalate- forms crystals in kidneys
sensitizer?
formaldehyde
asphyxiant?
carbon monoxide
teratogen?
acrylonitrile
carcinogen?
benzene
organ toxiant?
ethanol
neurotoxin?
acetone
poison?
cyanide
If a solid does not melt when placed in a capillary in a Digi-Melt, which of the following assumptions may be true
the Digi-melt doesn’t go up to a high enough temperature to melt the solid
The digi-melti is broken
there are three TLC plates the 1st one has three spots very close to the solvent front, the second as all three spots equally distance away from each other, the third has all three spots close to the baseline
which plate demonstrates the best separation of the mixture
2
there are three TLC plates the 1st one has three spots very close to the solvent front, the second as all three spots equally distance away from each other, the third has all three spots close to the baseline
Which eluent mixture was the molar polar?
1
there are three TLC plates the 1st one has three spots very close to the solvent front, the second as all three spots equally distance away from each other, the third has all three spots close to the baseline
Which eluent mixture has an intermediate polarity in comparison to the other two mixtures
2
Which of the following results indicates the product of the synthesis is vanillic acid? Note: The actual result may or may not be vanillic acid.
Rf from TLC is same as vanillic acid TLC from FS
solid is soluble in water
KNOW reduction half reaction and oxidation half reaction between vanillin/divanillin and hydrogen peroxide
know that the reduction half reactions are the same but the oxidation half difffers
what is the role of vanillin
limiting reagent
What is the role of acetic acid?
source of H+ for redox balance
What is the role of hydrogen peroxide?
oxidizing agent
What is the role of horeradish peroxidase?
catalyst
A student combined the following and stirred the solution for 10 minutes:
1.031 g of vanillin
2.20 mL 0.010 M acetic acid
9.0 mg horseradish peroxidase
7.5 mL of 3% H2O2
The precipitate which formed was collected by vacuum filtration and dried in the oven. Once the solid reached room temperature it is massed.
Answers should have the correct number of significant figures.
What is the theoretical yield (in grams) of: vanillin AND divanillin
VA: 1.139
DIV: 1.024
A student combined the following and stirred the solution for 10 minutes:
1.031 g of vanillin
2.20 mL 0.010 M acetic acid
9.0 mg horseradish peroxidase
7.5 mL of 3% H2O2
The precipitate which formed was collected by vacuum filtration and dried in the oven. Once the solid reached room temperature it is massed.
If 0.856 g of product is collected, what is the percent yield of:
VA: 75.1%
DIV: 83.6%
If the mass of the product is 1.374 g, the product is (more than one answer might be correct):
theoretical is (1.139 or 1.024)
wet and needs to be dried further in the oven
wet and needs to be dried further in the Buchner funnel
more than the theoretical
hazard?
potential source of danger
risk?
probability of suffering harm?
risk level?
hazard severity times exposure limit
risk assesment?
identification of sources of danger and probability of harm
risk management?
wearing personal protective equipment, avoiding spark sources, using smaller amounts
what are the factors that affect the probability of a lab accident?
how chemicals are used?
how other people behave?
how the physical environment is controlled?
which of the following must be assessed to reduce the probability of expose to a hazard
amount of chemical used, containment of chemicals, personal knowledge of chemicals, routes of exposure, type of personal protective equipment needed
While pouring 1 M of an aqueous potassium permanganate solution from a 1L reagent bottle, a student’s hand slipped and the bottle fell and broke open. A small amount of solution splashed onto the student’s eyes. The solution also spilled across the bench top and dripped down to create a pool on the floor.
a) If no safety precautions are followed the severity of the hazard is:
moderate
While pouring 1 M of an aqueous potassium permanganate solution from a 1L reagent bottle, a student’s hand slipped and the bottle fell and broke open. A small amount of solution splashed onto the student’s eyes. The solution also spilled across the bench top and dripped down to create a pool on the floor.
b) The probability of the event happening is:
possible
While pouring 1 M of an aqueous potassium permanganate solution from a 1L reagent bottle, a student’s hand slipped and the bottle fell and broke open. A small amount of solution splashed onto the student’s eyes. The solution also spilled across the bench top and dripped down to create a pool on the floor.
c) This leads to a risk level that is:
medium
While pouring 1 M of an aqueous potassium permanganate solution from a 1L reagent bottle, a student’s hand slipped and the bottle fell and broke open. A small amount of solution splashed onto the student’s eyes. The solution also spilled across the bench top and dripped down to create a pool on the floor.
d) Which measure should be taken to manage the risk?
all of the above
( know what to do if a chemical gets in the eyes,
know what to do if spill occurs,
wear goggles)
What happens after the crystallization process shown below in the Fundamental Skills section of the cinnamon project? Select all that apply.
the crystals are collected by vacuum filtration
the mass and melting point is recorded
What volume (in milliliters) of
acetophenone is needed to synthesize a sunscreen with 0.30 mL of cinnamaldehyde?
0.29 mL
What is the theoretical yield (in grams) of the sunscreen created from 0.30 mL of cinnamaldehyde and
acetophenone?
0.56
What volume (in milliters) of
acetone is needed to synthesize a sunscreen with 0.30 mL of cinnamaldehyde?
0.0876mL
What is the theoretical yield (in grams) of the sunscreen created from 0.30 mL of cinnamaldehyde and
acetone?
0.34 g
What is the percent yield is 0.29 g of the sunscreen is collected from the reaction of 0.50 mL of cinnamaldehyde and acetone?
51.1%
Which of the following would help you determine the severity of a hazard?
NFPA fire ratings, GHS symbols, PELs, lethal dose 50 values, chemical amount used
zero risk?
no hazard present
balancing ?
risk allowed increases with benefit of chemical use
technology-based?
exposure level is set to level it can be reduce to
eye hazards?
cause irreversible damage to cornea or iris
sensitizers?
cause hypersensitivity to lungs or skin
mutagens?
produce genetic defects
carcinogens?
cause cancer or presumed to cause cancer in humans
reproductive toxicants ?
cause birth defects
target organ toxicants?
cause damage to certain organs, affecting their ability to carry out normal functions
aspiration hazards?`
can be fatal if swallowed or inhaled
acute toxicants?
are fatal if exposed to the smallest amount
corrosives?
causes serve skin burns and eyes damage
Quiz 4 Session #1 Question 6 MUST MEMORIZE
Heptane and hexane have many similar chemical properties and hexane could be used in place of heptane for the TLC procedure. Why is heptane used for the TLC process instead of hexane?
a) hexane has more GHS pictograms
b) Hexane is a reproductie toxicant, heptane is not
c) hexane has a high vapor below room temperature
d) hexane’s flash point is at a lower temperature than heptane’s
e) three of these
f) all of these
E) THREE OF THESES
Which of the following characteristics would make a good sunscreen? (select all that apply.)
melting point value,
broad absorbance of ultraviolet light
ambient reaction conditions (little to no heat or pressure needed)
color and feel
high percent yield
low hazard starting materials
filtration materials?
filtrate
vacuum
buchner funnel
TLC materials?
eluent, silica plates, solvent front
crystallization materials?
temperature dependent solubility, no agitation
Match the separation process to the type of mixture being separated.
Filtration:
heterogeneous mixture
Match the separation process to the type of mixture being separated.
TLC:
mixture with components of different polarities
Match the separation process to the type of mixture being separated.
Crystallization :
products with impurities
Match the separation process to the project it could be used in:
Project #2 (Essential Oil):
TLC
Match the separation process to the project it could be used in:
Project #3 (Vanilla):
filtration and TLC
Match the separation process to the project it could be used in:
Project #4 (Cinnamon):
filtration, TLC, crystalization
Which of the following statements apply to green chemistry? (Select all that apply.)
methods used to eliminate hazards in during chemical use and manufacturing
high yield reactions are desirable
recycle reagents and solvents
choose reactions that can be done at room temperature and pressure
use less hazardous reagents
Which of the following statements about the chemicals or processes in Chem 1LD follow the principles of green chemistry? (Select all that apply.)
use of starting reagents (eugenol, vanillin, cinnamaldehdye) from renewable feedstocks
sunscreen synthesis did not require heat
Calculate the atom economy of reaction between cinnamaldehyde and acetophenone in project 2. (See Figure 2). Report your answer with 2 significant figures.
93%
