Instructions:
 Here's How to .....make a solution of a particular molarity.
CONCEPT: Molarity defines the
concentration of a solution. To make molarity measurable one needs to
convert formula weight of the chemical substance into grams. The weight of this
unit is known as a mole (Avogadro's Number). Unlike the mole pictured to
the left, in a chemical mole there are 6.02 x 10 23
atoms.
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Wear your
gloves and goggles and label all solutions! |
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To make a 1Molar
solution of a compound... Determine the mass required for
one
liter of the solution as follows:
- To determine the mass, find the formula weight for the
compound. Ex. for NaCl the FW is 58, combine the atomic mass of
Na (23) and Chlorine(35) = 58 grams
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| Balances need to
be zeroed - with the empty weighing pan on the balance, push the
tare button. Weigh
out the required mass (in the example above 58 grams of NaCl is necessary for an 1 molar solution).
Place desired mass into a
beaker or flask.
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Add about 80%
of the total amount of distilled water to the beaker, stir and
heat until dissolved. |
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To finish, add enough distilled water to the beaker to reach the
final volume needed. Reduce mass proportionally to the amount of volume needed.
Example: If you need 100ml of solution, mass would be 5.8 grams of NaCl
50 ml solution, mass = 2.9 grams of NaCl
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