Solid and Melting Point

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Solubility, Crystallization, and Melting Point Determination Pre-Lab Questions

(2pts) Indicate the correct waste container for the following compounds:

a. hexane - non-halogenated organic
b. 10% NaOH - aqueous
c. methylene chloride (dichloromethane) - halogenated organic
d. magnesium sulfate - solid
e. sodium hypochlorite - halogenated organic

2. (1pt) Describe the proper way to separate ground glass joints if they become stuck.
The proper way to separate ground glass joints is to hold the two pieces of glassware with paper towels so that your hands are touching as close to the joint as possible and pull with a firm grip. Try to loosen with a slight twisting motion. If that does not work try to tap with a wooden handle and try to pull apart. Lastly you can heat the joint with hot water or steam bath, but to be careful not to over heat.

3. (1pt) What is a solute? What is a solvent?

A solute is the solid that is dissolved in a liquid. The solvent is the liquid in which something is dissolved.

4. (1pt) What is the purpose of a water trap (used during vacuum filtration)?

The purpose of a water trap is to prevent filtrate from being sucked into the vacuum system.

5. (2pts) What is the difference between crystallization and precipitation of a product? List three differences.

Crystallization forms crystalline solids while precipitation produces amorphous solids. Crystallization is slow and a pure compound comes out of solution and precipitation is fast and a mixture of compounds falls out of solution. Crystals have an ordered structure than amorphous solids and are harder to produce.

6. (1pt) What will happen if you choose a solvent whose boiling point is higher than the melting point of the compound to be crystallized?

The solvent would boil out before the compound could melt.

7. (1pt) How does the melting point of a product help determine its purity?

The purer the material the higher its...
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