Chem Lab Skills Assessment prep

How to record a volume with of a beaker

No decimal points

“Approximately 10 mL”

How many decimals to record for an Erlenmeyer flask

No decimals

How to record volume of a graduated cylinder

Nearest .1mL

How to record volumetric pipet volume

• Record poppet volume with 2 places right of the decimal 10.00 mL

Precision for volumetric flask

Hundredths 50.00 mL

Percent error equation

| Experimental - actual | / actual times 100%

Melting point of a pure solid

2 degrees

How does the presence of an impurity affect the observed melting point range of a solid?

1. Broads the range

2. Lowers the range

Two steps to determine an accurate melting point reading

1. Obtain an approx melting point heating 5-10 degree per minute

2. Then do this more accurately increase fast until you are 20 degrees below the MP and then reduce the heating rate to 1-3 degree Celsius per minute

What happens when you heat a solid sample too quickly

-range will be higher

-range will be broader

Most to least precise glassware

Volumetric flask, vol burst, and pipet are most precise

Then grad cylinder and E. Flask

The least precise is a beaker

What would a mixture look like that you would describe as soluble?

If a solid dissolves in a liquid, resulting in a clear liquid with no visible solid, this is a homogenous mixture (solution)