Orgo Lab Exam #1

For a liquid, density is generally expressed in units of grams per ___________

Milliliter

Crushing a solid compound into a fine powder results in a _____ melting point range than melting one large crystal.

More accurate

While directly measuring a melting point in the lab, you should use a setting on the apparatus so that the temperature rises ___________ than ___ to ___ degrees per minute

No more; 2 to 3

Measuring the boiling point of a compound can be used to ________

confirm the compound's identity; assess the compound's purity

A mixture consisting of 50 mL of cylohexene and 50 mL of xylene is boiling in a round bottom flask. The vapors above the boiling liquid are

enriched in cyclohexene

An extraction __________ is a convenient way to display each of the steps of a reactive (or acid-base) extraction.

flow-chart

In the iodoform test, formation of a yellow precipitate indicates the presence of ___

Methyl Ketones

In a TLC test, if there is a presence of dark spots, then you know your compound contains __

Aromatic Ring

Rank the following possible types of intermolecular forces in organic compounds from lowest strength (1) to highest (4). A. 3 B. 1 C. 4 D. 2 1. ionic bonding 2. hydrogen bonding 3. dipole-dipole interactions 4. van der Waals dispersion forces

1. C 2. A 3. D 4. B

Beakers and Erlenmeyer flasks are good pieces of equipment to use for measuring an accurate volume. (T/F)

False

Water boils at _______ °C at sea level, but in Denver (5,000 ft) it boils at ______°C while on Mt. Everest (29,029 ft), boiling water only reaches ________°C.

100 °C, 93 °C , 72 °C.

Which size round bottom flask would be the best to use to perform a simple distillation on 25 mL of liquid?

100mL

Maleic acid and malonic acid have very similar names, and coincidentally, very similar melting point ranges. Maleic acid melts between 134-136 °C, and malonic acid melts between 135-137 °C. If a student inadvertently returned some malonic acid to the maleic acid jar, which of the following melting point ranges would you expect to find of the maleic acid mixture now?

130-135

If one is attempting to separate the components of a 50:50 mixture of benzene and xylene by simple distillation, around what temperature would one expect to collect the higher boiling component?

135?

How many fire extinguishers are located in the organic chemistry lab?

2

How many safety showers are located in the organic chemistry lab?

2

How many eye wash stations are located in the organic chemistry lab?

4

How many large sinks for washing hands and glassware are located in the organic chemistry lab?

4

Which size round bottom flask would be the best to use to perform a simple distillation on 25 mL of liquid?

50mL

At which of the following temperatures would benzoic acid be LEAST soluble in water?

??

By a linear extrapolation from the boiling points of methanol (64.7 ºC), ethanol (78.37 ºC), 1-propanol (97 ºC), 1-butanol (117.4 ºC), and 1-pentanol (137 ºC), predict the boiling point of 1-hexanol in degrees Celsius. _________________ Hint: The correct answer is slightly different from the measured, literature value of the boiling point.

??

The refractive index for a given compound depends on what? A. temperature B. pressure C. water D. wavelength

A,D

What is the name of the instrument that will be used in the lab to measure refractive index?

Abbe refractometer

Which of the following are we NOT performing a chemical test to confirm?

Alcohol

The boiling point of a liquid is defined as the temperature where the liquid's vapor pressure matches the _______________ pressure

Applied

Which of the following compounds has the highest boiling point? (BP&Density Lab) A. hexane B. 2-hexanol C. 2-methyl-2-pentanol D. 2-hexanone

B) 2-hexanol

Place the following four compounds in order of boiling point from lowest to highest. A. 1-pentanol B. 1-propanol C. 1-hexanol D. 1-butanol

B,D,A,C

What test would yield a positive result for 2-bromopentane?

Beilstein Test

What test would yield a positive result for 3-chloropentane?

Beilstein Test

The impure benzoic acid sample we will use in lab contains which of the following components?

Benzoic acid and Sodium Acetate

Which test would yield a positive result for 3-octene?

Bromination

What test(s) would give a positive result for methyl vinyl ketone?

Bromination Test; Iodoform Test

To perform a melting point determination, a small amount of powdered sample is placed inside a melting point ___________ tube.

Capillary

Where was the neutral component of the mixture at the end of your extraction?

Crystallized on the watch glass as solvent evaporated.

For a solid, density is generally expressed in units of grams per _____________

Cubic Centimer

Which of the following compounds has the highest boiling point? (BP&Density Lab) A. methanol B. ethanol C. 1-propanol D. 1-butanol

D) 1-butanol (117.5)

Which of the following compounds has the highest boiling point? (BP&Density Lab) A. 1-pentanol B. 2-pentanol C. 3-pentanol D. cyclopentanol

D) cyclopentanol

When measuring the volume or mass of an organic liquid, which of the following represents POOR laboratory practice? Select all that apply. A. Placing a disposable pipette directly into the stock bottle to obtain the liquid. B. Pouring the liquid to the approximate volume first, then adjusting with a disposable pipette. C. Inverting the disposable pipette to made sure no liquid drains out during the transfer. D. Using beakers or Erlenmeyer flasks for volume determination. E. Returning any excess to the stock bottle in order to prevent waste. F. Determining the mass of a container and then removing it from the balance before transferring a liquid into it.

D, E (another answer what is it?)

Branching in the hydrocarbon chain of an alcohol __________ the boiling point compared to an alcohol with a linear hydrocarbon portion.

Decreases?

Impure samples have melting point ranges that are both ___________________ and ____________ compared to a pure sample.

Depressed; Broadened

f 25 mL of dichloromethane is mixed with 25 mL of water, two layers will form and the _____________ layer will be on the bottom.

Dicholormethane

What types of intermolecular interactions are present in alkanes?

Dipole-Dipole?

A student performs a recrystallization similar to how we did it in lab to purify salicylic acid from sodium chloride using warm water as the solvent. After heating the mixture until all of the material dissolves, the solution cools and a white precipitate forms. The student then performs a vaccum filtration to separate the white precipitate from the solution. Where can the student find the sodium chloride?

Dissolved in the water filtrate

The boiling points in this experiment will be measured using a ____________ setup

Distillation

If 25 mL of ethyl acetate is mixed with 25 mL of aqueous sodium hydroxide, two layers will form and the ____________ layer will be on the top.

Ethyl Acetate

The phenomenon of melting point depression is used in every-day life during the winter whenever roads are salted. Ice and salt are mixed together to lower the melting point of water, making roads less slippery until colder temperatures. The precise composition of salt and ice to yield the lowest melting point temperature is with 23 wt% salt. This value is called the _________ point for a mixture

Eutectic

When organic molecules absorb radiant energy in the IR region, specific bonds within the molecule become __________ and ____________ .

Excited; Vibrate

Because the boiling points are within 40 °C of each other, it is possible to use simple distillation to completely purify the hexane from the toluene from the 50/50 mixture. (T/F)

False

Chewing gum is allowed in the lab. (T/F)

False

Eating and drinking is allowed in the lab. (T/F)

False

Given the same number of carbons, the general trend is that linear alcohols have lower boiling points than branched alcohols. (T/F)

False

Given the same number of carbons, the general trend is that primary alcohols have lower boiling points than secondary alcohols. (T/F)

False

Halogenated organic waste can be poured down the sink. (T/F)

False

If one accidentally takes too much reagent during an experiment, the excess amount should be returned to the container from which it came. (T/F)

False

If you mix compound A (melting point range: 43-44 °C) with compound B (melting point range: 44-45 °C), then you will observe the mixture to have a melting point range of 43-45 °C. (T/F)

False

If you take too much of a starting material, it is okay to put the excess back into the container from which it came. (T/F)

False

In the lab, melting points are measured as single temperature values. (T/F)

False

Non-mercury thermometers are just as accurate as mercury thermometers. (T/F)

False

The four chemical tests must be done in a specific order in order to work properly. (T/F)

False

In a Beilstein Test, if the color changes to green, then you know your compound contains ___.

Halogens

When distilling a 50/50 mixture of hexane and toluene, which of the two components in the mixture will you distill off first?

Hexane

A primary alcohol will have a __________ boiling point than a secondary alcohol with the same number of carbon atoms.

Higher

A primary organic alcohol will typically have a ______________ boiling point than the corresponding alkane with the same number of carbon atoms.

Higher

What is the source of the strongest intermolecular attractions in a sample of 1-heptanol?

Hydrogen Bonding

What is the source of the strongest intermolecular attractions in a sample of heptane?

Hydrogen Bonding

In the IR Spectroscopy test, you test for a presence of ___

Hydroxyl Group

What test would yield a positive result for 2-heptanone?

Iodoform Test

What tests would give a positive result for Tylenol?

Iodoform Test; TLC

What test(s) would give a positive result for benzylacetone?

Iodoform; TLC

In a Bromination Test, if the orange color fades and becomes colorless, then you know your compound contains __

Isolated Alkenes

The faster one performs a melting point determination, the _____ the melting point range will be.

Less accurate

In the Melting Point & Crystallization Lab, you will be using a ___________ apparatus to measure melting point ranges.

Mel-Temp

The ratio of concentrations of a solute in each layer is defined by the ____________ K.

Partition Coefficient

Where was the acidic component of the mixture at the end of your extraction?

Precipitated with HCl and vacuum filtered.

One should never heat a closed system due to the _______________________ that would build up, potentially leading to an _____________________ of the glassware.

Pressure; Explosion

Because the presence of impurities lowers the melting point, the melting point can be a good indicator of purity: the_________ the material, the ________ its melting point, and the __________ the melting point range.

Purer; Higher; Narrower

Melting points are always measured as a _________

Range

What piece of glassware is used to perform liquid-liquid extractions?

Separatory Funnel

Density is the ______ of the graph

Slope

In liquid-liquid extraction, separation of the compound of interest is based on its

Solubility

What physical property of organic compounds does recrystallization exploit to achieve purification?

Solubility

Crystals grow from _______________ solutions

Supersaturated

What test would yield a positive result for benzyl alcohol?

TLC Test

What piece of glassware will you use for the bromination test?

Test Tube

Why is benzoic acid more soluble in a basic aqueous solution than it is in neutral water?

The base deprotonates the carboxylic acid, and the anion form is more soluble than the neutral form.

Benzoic acid is more soluble in 5% aqueous sodium hydroxide than it is in water. (T/F)

True

If a separatory funnel contains benzene and water, the water will be the bottom layer. (T/F)

True

If a separatory funnel contains cyclohexene and water, the water will be the bottom layer. (T/F)

True

Impurities should be more soluble in the solvent than the desired material. (T/F)

True

No food or drink should ever be brought into the lab. (T/F)

True

One must always wear a lab coat and goggles while chemicals are out in the lab. (T/F)

True

The boiling point of a liquid is dependent on pressure. (T/F)

True

The general trend is that increasing number of carbon atoms leads to an increase in the boiling point of a compound. (T/F)

True

When working with chemicals in the lab, one should always wear socks that cover the ankles and closed-toed shoes. (T/F)

True

The major safety hazard with the Beilstein test is what?

Using the Bunsen burner with the highly flammable test compounds

What is the step we will use to physically separate and collect the recrystallized benzoic acid?

Vaccuum Filtration

What types of intermolecular interactions are present in alcohols?

Van Der Waals; Dipole-Dipole; Hydrogen

The boiling point of a liquid is defined as the temperature at which the ______________ of the liquid equals atmospheric pressure.

Vapor Pressure

The temperature of a pure boiling liquid is equal to the temperature of the ________ above the liquid

Vapors

Density is defined as mass per unit ______

Volume

When performing liquid-liquid extractions, the bottom layer should be removed through the _________ , and the top layer should be removed through the __________ .

bottom; top

The normal boiling point of a compound is measured at standard pressure, which is equal to 760 _____ or 1 ______.

mmHg; atm

Organic acids and bases in their _________ form are soluble in organic solvents, but the corresponding __________ are more water-soluble. Therefore, converting acids and bases to the corresponding _________ provides a convenient tool to separate acidic, alkaline and neutral organic compounds.

neutral; salts; salt

In terms of lab safety and lab rules, being aware of and taking precautions against potential hazards is the best way to ______________________________________ .

prevent accidents before they happen

In order to safely work in this organic chemistry lab, one should always wear:

protective eye wear, such as safety goggles or glasses; a full length laboratory coat; . closed-toed, closed-heel shoes; disposable nitrile gloves; full-length pants or skirt

A(n) ____________________ extraction involves changing the polarity (and therefore solubility) of a compound using acid/base chemistry.

reactive

Distillation is the process of __________ a liquid, _____________ the vapor, and _____________ the condensate in another container.

vaporizing; condensing; collecting