J5: Supplemental Problems Worksheet
Mole Calculations, Percentage Composition, Empirical And Molecular Formula
Determination
MOLE CALCULATIONS (J-2 WRITTEN ASSIGNMENT):
In order to answer the following questions, you must first calculate the molar mass, and write the full
three-part equivalency. Make sure to show all work (equivalencies, set-ups, cancellation of units). All
answers should be in the correct units, with the correct number of significant figures.
1.
A)
2.
A)
3.
How many moles of compound are there in the following?
6.60 g (NH4)2SO4
B)
4.5 kg Ca(OH)2
B)
125 g C12H22O11
How many molecules are there in the following?
25.0 g H2SO4
Ibubrofen, C13H18O2, is the active ingredient in many nonprescription pain relievers
A) If the tablets in a bottle contain a total of 33.00 g of ibuprofen, how many moles of ibuprofen are in the
bottle?
B) How many molecules of ibuprofen are in the bottle?
C) What is the total mass in grams of carbon in 33.00 g of ibuprofen?
PERCENTAGE COMPOSITION PROBLEMS
4.
A 40-gram iron oxide sample is analyzed and found to contain 28 g of iron, and 12 g of oxygen. What
is the percentage composition of this iron oxide sample?
5.
A sample of a compound is found to contain 53.0 g of sodium and 37.0 g of oxygen. What is the
percentage composition of this compound?
6.
Determine the percentage composition of the compound silver nitrate (you must know how to write the
formula to do this).
7.
Determine the percentage composition of magnesium hydroxide (you must know how to write the
formula to do this).
EMPIRICAL AND MOLECULAR FORMULA PROBLEMS
8.
What is the empirical formula for a compound sample if it consists of 14.0 g of nitrogen, and 8.00 g of
oxygen?
9.
An iron-oxygen compound is analyzed and found to contain 112 g of iron, and 48.0 g of oxygen.
Determine the empirical formula of this compound.
10. Chemical analysis of citric acid shows that it contains 37.51% C, 4.20% H, and 58.29% O. Determine
the empirical formula of this compound.
11. The percentage composition of chromium-oxygen compound is 68.4 % chromium, and 31.6% oxygen.
Determine the empirical formula of this compound.
12. Oleic acid has the empirical formula C9H17O. If the experimental molar mass is 282 g, what is the
molecular formula of oleic acid?
13. The molar mass of the compound nicotine is 162.1 g. A sample of nicotine contains 74.0% C, 8.7% H,
and 17.3% N.
A) Determine the empirical formula of nicotine.
B) Determine the molecular formula of nicotine.