CHEM 235 Written Examination

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Chewing gum in the lab can cause absorption of fumes from the air into your mouth.

Why is chewing gum inadvisable in the organic chemistry laboratory?

Fire.

What is considered the greatest danger in undergraduate organic laboratories?

Workplace Hazardous Materials Information System

What does WHMIS stand for?

Compressed Gas; Flammable and Combustible Material; Oxidizing Material; Poisonous and Infections Material - Materials causing immediate and serious toxic effect and Materials causing other toxic effects; Biohazardous Infectious material; Corrosive Material; Dangerously Reactive Material

What are the WHMIS hazard classes?

Hazardous Ingredients; Product Information; Physical Data; Fire or Explosion Information; Reactivity Data; Toxicological Properties; Preventive Measures; First Aid Measures; MSDS Preparation Information

What information does MSDS provide?

In distillation, the condensate (distillate) is collected in a separate vessel called the receiver, whereas in refluxing, the condensate returns to the original container.

How is distillation different from refluxing?

When the components of the mixture have different boiling points.

When is distillation useful for separating a mixture?

When at least one component in the mixture is volatile and the components must not form an azeotrope.

When is distillation appropriate?

A mixture of two (or more) liquids that distills at a constant temperature with a constant composition.

What is an azeotrope?

The temperature at which the total vapour pressure is equal to the atmospheric pressure.

What is the definition of a boiling point?

The measure of change in the light path as light paces at an angle from one medium to another.

What is a refractive index?

Wavelength of light and temperature.

What is refractive index dependent upon?

n(T1) = n(Tobs) + (0.00045) (Tobs -T1)

How do you correct an observed refractive index?

Placing the thermometer in a beaker containing a well-stirred slurry of crushed ice and water, ensuring that the immersion line on the thermometer is covered by the liquid. Check the temperature reading on the thermometer after a few minutes and note if the thermometer does not read zero degrees celsius.

What is the correct way to calibrate a thermometer?

Use a boiling chip.

How do you avoid bumping?

Boling chips are alundum granules that have trapped air inside. When heated, they release the air, allowing boiling to occur in a liquid without bumping

What is a boiling chip and how does it work?

One drop per second.

What is a good rate for refluxing or distillation?

The first solvent should complete dissolve both compounds. The second solvent must be immiscible with the first solvent and should dissolve only one component of the mixture.

What are qualities of good extraction solvents?

No more than two-thirds the volume of the funnel.

How much liquid may be added to a separatory funnel?

A finely dispersed suspension of one liquid layer in another.

What is an emulsion?

Wait for a few minutes or, if water is one of the solvents, adding saturated NaCl.

How do you get rid of an emulsion?

Drying agents are inorganic salts that can form hydrates used to dry organic liquids. They can include magnesium sulfate or sodium sulfate.

What is a drying agent and what are some examples?

Evaporation on a steam or hot water bath; evaporation at reduced pressure; distillation or by use of the rotary evaporator.

What are some ways of removing an organic solvent from a desired compound?

Must dissolve the compound only sparingly or not at all at room temperature but readily at the boiling point. Cannot react chemically with the compound. Should dissolve impurities exceedingly well or not at all. Should have a boiling point lower than the meling point of the solid to be purified.

What are the requirements for a good recrystallization solvent?

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