1. When taking a melting point, why is it important that the the temperature doe
ID: 800717 • Letter: 1
Question
1. When taking a melting point, why is it important that the the temperature does not rise too rapidly? Choose as many that apply
A. To prevent decomposition of the sample?
B. So that the sample will be at the temperature indicated by the instrument
C. So that the compound doesn't melt so rapidly you miss it
D.So that the melting point capillary doesn't break
2. When extracting an organic product into an organic solvent, which are not reasons to add brine to the aquesous layer or wash the organic layer with brine? (Choose as many as don't apply)
A. To reduce the amount of water dissolved in the organic layer
B. To decrease the amount of unwanted (Non-Product) polar compounds in the organic layer.
C. To decrease the amount of organic compounds in the organic layer
D. To help break or prevent emulsions
E. To increase the solubility of organic compounds in the organic layer.
F To neutralize any acids present, thus preventing them from entering the organic layer
3. When extracting an organic product into an organic solvent, which are reasons to wash the organic layer with 5% aquesous sodium bicarbonate? (Choose as many that apply)
A. To reduce the amount of water dissolved in the organic layer
B. To decrease the anmount of unwanted (non-product) polar compounds in the organic layer
C.To decrease the amount of organic compounds int he organic layer
D. To help break or prevent emulsions
E. To increase the solubility of organic compounds in the organic layer
F. To neutralize any acids present, thus preventing them from entering the organic layer
4. When Extracting an aquesous layer witha n organic layer, which of the following are true? (Choose as many that apply)
A. If the organic solvent used is dichloromethane, the desired layer will be on top
B. Multiple extractions are generally used to increase the efficiency and yield of the extraction process.
C. If the organic solvent used is hexanes,
D. When using multiple extractions, you leave some organic layer behind every time except the last, when you take a bit of the aquesous layer (If you have to)
E. The difference between an extraction and a wash is which layer you keep
5. Why are some steam baths often used to evaporate organic solvents? (Choose as many as apply)
A. To reduce the chance of igniting the solvent
B. To prevent the product from boiling away.
C. TO limit the temperature experienced by the organic solution
D. becasue it is faster and more convenient than a hot plate.
6. Which is a potential safety hazard when using a thermowell? (Choose as many as apply)
A. It could break the round bottom flask.
B. It could ignite the organic liquid
C. If plugged directly into the wall socket, it could overheat
D. If poorly maintaned, it could shock the user
7. Which are different categories of chemical waste used in organic chemistry? (Choose as many as apply)
A. Organic/Acid waste
B. Heavy metal waste
C. Permanganate waste
D. Halogenated solvent waste.
E. Ether waste
8. When subliming caffeine, why is the pressure inside the sublimination apparatus reduced? Choose as many that apply)
A. To increase the Vapor pressure of the caffeine
B. To prevent the chlorophyll from subliming
C. To decrease the surface are where the hydrogen gas contacts the organic solution
D. To allow the caffeine to condense on the cold finger
9. Why do you use a narrow-guage needle when hydrogenating? (Choose as many as apply)
A. To reduce the amount of organic solution sucked up by the needle.
B. To reduce the amount of time required to hydrogenate the compound.
C. To increase the surface area where the hydrogen gas contacts the organic solution.
D. To reduce the chance of clogging the needle with the catalyst
10. Which is a potential safety hazard when using 10% Pd/C? (Choose as many as apply)
A. It can spontaneously ignite on contact with glass.
B. It can spontaneously ignite on cantact with metal.
C. it can spontaneously ignite on contact with wet paper.
D. It makes the organic solution more flammable.
11. What causes infrared absorption peaks? ( Choose as many as apply)
A. Intermolecular Forces
B. Differences in molecular weight
C. Nuclear Spin
D. Molecular Vibrations
E. Chirality
Explanation / Answer
1. A,c
2. B,E,F
3.B,C,E
4.C,E
5.A,C,D
6.C,D
7.A,C
8.B,D
9.D
10.A,D
11.C,D
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