Chemistry Exam
Percent Composition and Molecular Formula
Lab Date: Friday 2/6/2011
PRE-LAB
A 3.45 g sample of Titanium (Ti) is burned in the presence of oxygen to produce
5.76 g of Titanium Oxide.
1.)
Determine the % composition of each of the elements in TixOy
2.)
Determine the Empirical Formula for TixOy
3.)
Determine the Molecular Formula TixOy.
is 79.88 g/mol.
4.)
Write the balanced equation for the combustion of Titanium.
5.)
Determine the limiting reagent
6.)
Determine the theoretical yield of the product.
7.)
Determine the % yield of the product.
8.)
On a separate sheet of paper, develop a flow cart for your lab using the
procedures outlined in the lab.
9.)
On a separate sheet of paper, develop a data collection table for
your lab. Be sure to include thorough labels and a ruler for neatness.
Also, include a space for a clean-up and safety signature.
the molar mass for titanium oxide
10.) A single replacement reaction occurs between copper chloride and zinc
metal. What is the solid precipitate that is produced? (You do not know the
charge of the copper metal, so therefore you cannot write a balanced equation,
but you can predict the precipitate. Use CuxCly for the formula for Copper
Chloride.
MRS. PHELAN’S ROLE IN YOUR EXAM
Ensure safety
Supply materials and/or chemicals
Time management
Not to provide instruction as to how to collect data and complete equations.
PROCEDURE
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15.)
Obtain approximately 5.0 grams of Copper Chloride and place it
in a clean, dry beaker. Record the exact mass in a data table.
Add 25 ml of distilled water to the Copper Chloride
Measure the mass of a small sample of Zinc metal. The mass should be
approximately 5.0 grams. Record the mass in a data table.
Add the Zinc metal to the Copper Chloride Solution. Stir with a stir
rod until the reaction stops.
Carefully add 5 drops of Hydrochloric Acid (CAUTION- May cause burns!)
Carefully remove the Zinc metal using a tweezers. Rinse the Zinc into
the beaker using distilled water.
Using paper towel, dry the Zinc metal and record the mass in a
data table.
Carefully decant the remaining liquid from the beaker into another
beaker. Try not to lose the precipitate. Rinse the precipitate with
distilled water and decant again.
Rinse the precipitate with acetone and decant the acetone into
the organic wastes container.
Repeat the acetone rinse one more time and decant the acetone.
Obtain a clean, dry evaporating dish. Record the mass in a data
table.
Using a rubber spatula, transfer the precipitate into an evaporating
dish. Use acetone to rinse any remaining precipitate into the
evaporating dish.
Heat and dry the precipitate in the evaporating dish over a beaker of
hot water. Be sure the precipitate is completely dry. This may take
up to 5-10 minutes.
Record the mass of the evaporating dish and the precipitate.
Clean up your area. Wash all the dishes and place them on a
clean paper towel to dry. Wash your counter space with spray
and make sure the sink is clean too. The supernatant from step 8 can
go into the drain. Fold your aprons and return them to the corner of
your workspace.
HINTS FROM MRS. PHELAN
Use the percent composition to determine the amount of chlorine in copper
chloride.
The molar mass of the copper chloride compound produced is 134.45 g/mol.
Remember that adding water turns the copper chloride into an aqueous
solution. This does NOT affect your reaction!
The mass of the Copper you record at the end includes the evaporating dish!
SHOW ALL YOUR WORK FOR FULL CREDIT!!!!!!!!
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