CHEM 237 Prelab Quizzes for Exam Review

The electronic geometry of an sp3 carbon is:

tetrahedral

TLC spotters are capillary tubes and so they should be disposed of in the....

glass waste

For the Dehydration of Cyclohexanol Experiment: Put the following in order

highest boiling temperature pure cyclohexanol cyclohexanol/water azeotrope pure cyclohexene cyclohexene/water azeotrope lowest boiling temperature

Which of the following is a negative aspect of the method of recrystallization?

incompatible with oils

A student was given a sample of crude acetanilide to recrystallize. The initial mass of the crude acetanilide was 204 mg. The mass after recrystallization was 139 mg Calculate the percent recovery from recrystallization (one decimal place).

68.1

When equilibrating between conformations of cyclohexane (a chair-flip), axial substituents trade places and stay as axial substituents.

False

If your skin comes into contact with the sulfuric/phosphoric acid mixture, which of the following should you do?

Wash the affected area with sodium bicarbonate solution Wash the affected area with cold water Let your TA know

If an irritant makes contact with your skin, which of the following actions should you take?

Wash the area with water Alert your TA

Which of the following is not among the standard conformations of butane?

semi-eclipsed Standard: anti and gauche

For the TLC Experiment: Chromatography is a technique that is used to ________ different compounds

separate sort and mix Methods for identification, isolation, and purification. Can also monitor a reaction

The sample is dissolved in hot solvent then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. What effect will result if the filtrate solution is cooled too rapidly?

small impure crystals will form

The different geometries that a molecule can attain by bond rotations and bends are called conformations.

True

For a given molecule, when the molecule deviates from its non-ideal geometry, the non-ideal geometry is lower in energy than the ideal geometry

False

For the Recrystallization Experiment: Molecules of a pure compound tend to form the best crystal lattice

True

Distillation separates compounds on the basis of....

boiling point

Which of the following are representations of organic molecules?

plastic models skeletal structures computational models

Which of the following are possible vibrations associated with water?

symmetric stretching scissoring (bending) asymmetric stretching

For the Dehydration of Cyclohexanol Experiment: What is the most stable carbocation?

tertiary

As compared to pure compounds, impure compounds....

have a melting point that encompasses a wider temperature range

Mary ran a sample on a TLC plate. The spot associated with the sample travelled a distance of 1.00 cm while the difference between the origin and the solvent front was 4.95 cm. Calculate the Rf of the sample. Give your answer to two decimal places.

0.20

For the Kinetics Experiment: A reaction that has two molecules involved at the rate determining step normally has an overall reaction order equal to....

1

Match the component with its role in Thin-Layer Chromatography

Beaker or Bottle with Solvent - TLC Chamber Glass, Plastic, or Aluminum Plate - Solid Back Solvent - Moblie phase Silica Gel or Alumina - Stationary Phase

For the Extraction Experiment: Typically organic compounds will be soluble in the organic phase.

True

For the Phase Transfer Catalysis Experiment: Agents that can transfer reactants between the aqueous and organic phases are called phase transfer catalysts.

True

The Molecular mechanics model substitutes springs for bonds and balls for atoms

True

The computations based upon the quantum mechanics model take longer and are more rigorous.

True

When venting your separatory funnel, direct the spout at the hood.

True

Aqueous washes should be disposed of by pouring them down the drain.

True or False

Organic solvents can be poured down the drain.

True or False

While attempting to determine the structure of a compound using elemental analysis and functional group tests, you are generally able to recover your original sample.

True or False

Understanding the mechanism of a reaction can lead to:

Understanding the rate of reaction Possible development of a catalyst for the reaction Optimizing the number of fast and slow steps Optimizing the reaction conditions for improved yields

For the Recrystallization Experiment: Which of the following techniques are used in this experiment?

Vacuum Filtration Recrystallization

For the Phase Transfer Catalysis Experiment: When running a pipet column with silica gel, what is the correct order in which compounds will elute out of the column?

least polar compounds, medium polar compounds, most polar compounds

For the TLC Experiment: Compounds that have the _____ affinity for the stationary phase and _____ affinity for the mobile phase will travel the furthest.

lowest, greatest In a nonpolar solvent: low affinity to the stationary phase means they are nonpolar because they don't want to retain to the plate that is polar high affinity to the mobile phase (solvent) means they will retain with the solvent and move the most high affinity to the stationary phase means they are polar because they want to retain to the polar plate low affinity to the mobile phase (nonpolar solvent) means they won't retain to the solvent due to the different polarity making them travel the least = travels the least

For the Extraction Experiment: After benzocaine is mixed with sodium hydroxide, it will be _______ and soluble in the ________.

neutral, organic layer