Page 1 of 171
OCHEM LAB FINAL EXAM REVIEW EXAM TEST
BANK ALL WITH 450 QUESTIONS AND
CORRECT DETAILED SOLUTIONS JUST
RELEASED THIS YEAR
QUESTION: In the extraction lab, How will you recover the naphthalene from its solution at the
end of the extraction?
a. By adding an acid to the solution
b. Filter the solvent
c. Evaporate the solvent
d. By adding water to the solution - ANSWER✔✔Evaporate the solvent
QUESTION: True or False? During the extraction procedure, the organic layer will be on the top
layer. - ANSWER✔✔True
QUESTION: Benzoic acid (an organic acid) is soluble in which of the following organic solvents?
a. Diethyl ether
b. water
c. Sodium hydroxide (NaOH 6M)
d. all of the above - ANSWER✔✔Diethyl ether
, Page 2 of 171
QUESTION: Suppose, the weight of the unknown mixture you started with is 142.3 mg. The
weight of the extracted benzoic acid is 41.7 mg. The weight of the extracted naphthalene is 48.8
mg. You can combine the weights of the chemicals you isolated and compare that weight to the
weight you started with to determine a percent recovery. Calculate the extraction recovery
efficiency (i.e. percent recovery).
Equation: % recovery = (combined weight of the isolated compounds/weight of the starting
mixture) x 100
a. 93.5%
b. 83.5%
c. 73.5%
d. 63.5% - ANSWER✔✔63.5%
QUESTION: Your recovery is highly unlikely to be exactly 100%. Which of the following are
possible reasons why your recovery is less than 100%?
a. Mechanical losses (e.g. during transfers)
b. Incomplete deprotonation
c. incomplete reprotonation
d. All of the above are possible reasons! - ANSWER✔✔All of the above are possible reasons!
, Page 3 of 171
QUESTION: Suppose, after extraction, you did not allow enough time for the recovered benzoic
to dry. Therefore, it was still wet when you measured its weight and calculated the percent
recovery. Which of the following do you think might be your value for percent recovery?
a. <100%
b. >100%
c. Cannot be determined. Need more information. - ANSWER✔✔>100%
QUESTION: Which technique will you use to determine the purity of a solid sample?
a. mixed melting point
b. melting point
c. boiling point
d. mixed boiling point - ANSWER✔✔melting point
QUESTION: In the meling and boiling point lab, which technique did you use to determine the
identity of a solid sample?
a. mixed melting point
b. melting point
c. boiling point
, Page 4 of 171
d. mixed boiling point - ANSWER✔✔mixed melting point
QUESTION: will an impurity increase or decrease the melting point temperature of a pure
sample?
a. increase
b. decrease - ANSWER✔✔decrease
QUESTION: will an impurity increase or decrease the melting point range of a pure sample?
a. increase
b. decrease - ANSWER✔✔increase
QUESTION: Which technique will you use to determine the identity of a liquid sample?
a. mixed melting point
b. melting point
c. boiling point
d. mixed boiling point - ANSWER✔✔boiling point
QUESTION: What should the melting point range be for a pure substance?
a. 3-5 degrees C
OCHEM LAB FINAL EXAM REVIEW EXAM TEST
BANK ALL WITH 450 QUESTIONS AND
CORRECT DETAILED SOLUTIONS JUST
RELEASED THIS YEAR
QUESTION: In the extraction lab, How will you recover the naphthalene from its solution at the
end of the extraction?
a. By adding an acid to the solution
b. Filter the solvent
c. Evaporate the solvent
d. By adding water to the solution - ANSWER✔✔Evaporate the solvent
QUESTION: True or False? During the extraction procedure, the organic layer will be on the top
layer. - ANSWER✔✔True
QUESTION: Benzoic acid (an organic acid) is soluble in which of the following organic solvents?
a. Diethyl ether
b. water
c. Sodium hydroxide (NaOH 6M)
d. all of the above - ANSWER✔✔Diethyl ether
, Page 2 of 171
QUESTION: Suppose, the weight of the unknown mixture you started with is 142.3 mg. The
weight of the extracted benzoic acid is 41.7 mg. The weight of the extracted naphthalene is 48.8
mg. You can combine the weights of the chemicals you isolated and compare that weight to the
weight you started with to determine a percent recovery. Calculate the extraction recovery
efficiency (i.e. percent recovery).
Equation: % recovery = (combined weight of the isolated compounds/weight of the starting
mixture) x 100
a. 93.5%
b. 83.5%
c. 73.5%
d. 63.5% - ANSWER✔✔63.5%
QUESTION: Your recovery is highly unlikely to be exactly 100%. Which of the following are
possible reasons why your recovery is less than 100%?
a. Mechanical losses (e.g. during transfers)
b. Incomplete deprotonation
c. incomplete reprotonation
d. All of the above are possible reasons! - ANSWER✔✔All of the above are possible reasons!
, Page 3 of 171
QUESTION: Suppose, after extraction, you did not allow enough time for the recovered benzoic
to dry. Therefore, it was still wet when you measured its weight and calculated the percent
recovery. Which of the following do you think might be your value for percent recovery?
a. <100%
b. >100%
c. Cannot be determined. Need more information. - ANSWER✔✔>100%
QUESTION: Which technique will you use to determine the purity of a solid sample?
a. mixed melting point
b. melting point
c. boiling point
d. mixed boiling point - ANSWER✔✔melting point
QUESTION: In the meling and boiling point lab, which technique did you use to determine the
identity of a solid sample?
a. mixed melting point
b. melting point
c. boiling point
, Page 4 of 171
d. mixed boiling point - ANSWER✔✔mixed melting point
QUESTION: will an impurity increase or decrease the melting point temperature of a pure
sample?
a. increase
b. decrease - ANSWER✔✔decrease
QUESTION: will an impurity increase or decrease the melting point range of a pure sample?
a. increase
b. decrease - ANSWER✔✔increase
QUESTION: Which technique will you use to determine the identity of a liquid sample?
a. mixed melting point
b. melting point
c. boiling point
d. mixed boiling point - ANSWER✔✔boiling point
QUESTION: What should the melting point range be for a pure substance?
a. 3-5 degrees C
