Lab Quizzes Q+A

Question 1

What is the main purpose of recrystallization in organic chemistry?

Answer 1

To purify organic solids by removing impurities

Question 2

What is the significance of slower cooling during the recrystallization process?

Answer 2

It produces larger and purer crystals

Question 3

What is the role of vacuum filtration in recrystallization?

Answer 3

To dry the crystals by removing residual solvent

Question 4

Why is water chosen as the solvent for recrystallization in this experiment?

Answer 4

It has ideal solubility properties for acetanilide

Question 5

In melting point analysis, what happens if the sample is wet?

Answer 5

The observed melting point is lower and inaccurate

Question 6

Google the structure of thebaine. If added to a biphasic mixture of diethyl ether and 1.0M NaOH, where would thebaine partition?

Answer 6

Preferentially into the organic layer

Question 7

How does the rotovap efficiently evaporate solvents?

Answer 7

It reduces pressure, heats, and spins the sample

Question 8

Can excess diethyl ether be disposed of in the sink?

Answer 8

NO

Question 9

Was diethyl ether removed by vacuum filtration in the extraction lab?

Answer 9

No

Question 10

Is diethyl ether flammable?

Answer 10

Oui

Question 11

Magnesium sulfate (MgSO4) was used in the extraction lab to absorb trace amounts of water from the organic layer (diethyl ether). How much magnesium sulfate was added?

Answer 11

Correct amount was determined by observation. MgSO4 was added until the salt no longer clumped and there was no visible water in the flask

Question 12

What was the purpose of performing a melting point analysis of the unknown carboxylic acid in the unknown carboxylic acid lab?

Answer 12

To identify the acid by comparing its melting point with known values

Question 13

In the unknown carboxylic acid lab, what observation indicated the presence of nitrogen in the unknown acid following sodium fusion?

Answer 13

A deep blue precipitate that appeared after adding ferrous ammonium sulfate and sulfuric acid

Question 14

Was the use of an open flame to heat the apparatus a direct hazard associated with the sodium fusion process in the unknown carboxylic acid lab?

Answer 14

Yes

Question 15

Was the handling of hot glassware during and after the operation a direct hazard associated with the sodium fusion process in the unknown carboxylic acid lab?

Answer 15

Yes

Question 16

Was the generation or use of a strongly acidic solution, specifically 6M sulfuric acid (H2SO4) a direct hazard associated with the sodium fusion process in the unknown carboxylic acid lab?

Answer 16

No, it was in indirect hazard

Question 17

Was the reactivity of sodium metal used in the fusion process a direct hazard associated with the sodium fusion process in the unknown carboxylic acid lab?

Answer 17

Yes

Question 18

Why was it necessary to acidify the filtrate before performing the chemical tests for sulfur, nitrogen, and halogen in the unknown carboxylic acid lab?

Answer 18

To adjust the pH to a level suitable for each specific test reaction

Question 19

What was the correct method for disposing of test tube contents after performing the chemical tests for sulfur, nitrogen, and halogen in the unknown carboxylic acid lab?

Answer 19

Test tubes were emptied into specifically labeled collection vessels

Question 20

In gas chromatography, what serves as the mobile phase?

Answer 20

An inert gas

Question 21

True or false: when handling the syringe for injecting the sample into the gas chromatography apparatus, the syringe should be rinsed thoroughly with water before each injection

Answer 21

False

Question 22

True or false: when handling the syringe for injecting the sample into the gas chromatography apparatus, the syringe needle should be inserted slowly into the injection port to avoid damaging the septum

Answer 22

True

Question 23

True or false: when handling the syringe for injecting the sample into the gas chromatography apparatus, the plunger should be rapidly pushed down when injecting the sample

Answer 23

False

Question 24

True or false: when handling the syringe for injecting the sample into the gas chromatography apparatus, the syringe should be reused multiple times without rinsing

Answer 24

False

Question 25

If a gas chromatogram shows a broad, poorly resolved peak, what is the most likely cause?

Answer 25

The sample was overloaded or injected improperly

Question 26

What is the function of the detector in a gas chromatography apparatus?

Answer 26

To identify and record compounds as peaks on a chromatogram

Question 27

Why was it important to rinse the syringe multiple times before injecting a new sample into the gas chromatography apparatus?

Answer 27

To remove residue from the previous sample, preventing contamination

Question 28

In the distillation lab, what technique was used to analyze the composition of the distillate?

Answer 28

Gas chromatography

Question 29

Why should the distillation apparatus be inspected before turning on the heat source?

Answer 29

To verify the setup is safe and there are no leaks

Question 30

What should be done if the distillation rate is too fast?

Answer 30

Lower the hot plate temperature

Question 31

At the beginning of the distillation, what is the nature of the vapor phase compared to the nature of the liquid phase?

Answer 31

The vapor phase is richer in the component with the lower boiling point

Question 32

What is the role of the condenser in the distillation apparatus?

Answer 32

To cool and condense the vapor back into liquid form

Question 33

What is the primary purpose of TLC?

Answer 33

To separate and identify components of a mixture

Question 34

How does a polar compound behave on a silica TLC plate with a nonpolar mobile phase?

Answer 34

It stays near the baseline

Question 35

Which type of compound is most likely to travel the farthest up a silica TLC plate when using a nonpolar solvent?

Answer 35

A nonpolar hydrocarbon with only carbon and hydrogen atoms

Question 36

What is the function of iodine vapor in TLC analysis?

Answer 36

It stains compounds to make them visible

Question 37

For TLC, if the mobile phase is made more polar, what will likely happen to the Rf values of polar compounds?

Answer 37

They will increase

Question 38

What is the primary purpose of performing distillation in the IUAK lab?

Answer 38

To obtain a pure sample and determine the boiling point

Question 39

Which test specifically identifies methyl ketones?

Answer 39

Iodoform test

Question 40

What indicates a positive Tollens' test?

Answer 40

Formation of a silver mirror or black precipitate

Question 41

In the TLC lab, what was the purpose of using the vacuum filtration setup in the semicarbazone preparation?

Answer 41

To dry and collect the crystalline derivative

Question 42

True or false: boiling point of the compound was directly determined during the TLC lab procedure

Answer 42

True

Question 43

True or false: melting point of the semicarbazone was directly determined during the TLC lab procedure

Answer 43

True

Question 44

True or false: molecular weight of the unknown was directly determined during the TLC lab procedure

Answer 44

False

Question 45

True or false: results of chemical tests (Tollens' and iodoform) was directly determined during the TLC lab procedure

Answer 45

True