Ch. 6 Chemistry Examples (Blue)
1. Calculate the number of copper atoms present in a sample that has a mass of 1779.4 amu.
2. Calculate the number or argon atoms present in a sample that has a mass of 3755.3 amu.
3. Calculate the number of moles of atoms and the number of atoms in a 25.0 g sample of calcium.
4. Calculate the number of moles of atoms and the number of atoms in a 57.7 g sample of sulfur.
5. Calculate the number of atoms in a 23.6 mg sample of zinc.
6. Calculate the number of atoms in a 128.3 mg sample of silver.
7. Find the mass of:
a. 0.25 mol of Al
b. 0.500 mol Au
c. 5.0 mol Fe
d. 25 mol S
7. Find the molar mass for each of the following:
a. Water, H2O e. CaSO4
b. Ammonia, NH3 f. Na2CO3
c. Propane, C3H8 g. Ba(OH)2
d. Glucose, C6H1206
8. Calculate the mass of 1.48 mol of potassium oxide.
9. Calculate the mass of 4.85 mol of acetic acid HC2H3O2. Vinegar is a dilute solution of acetic
10. Formaldehyde, which in the past was used to preserve biological samples, has the formula
H2CO. How many moles of formaldehyde does a 7.55 g sample represent?
11. How many moles of tetraphosphorus decoxide does a 250.0 g sample represent?
12. How many water molecules are in a 10.0 g sample of water?
13. Sucrose, or table sugar, has the formula C12H22O11. How many molecules of sugar are in a 5.00
lb bag of sugar?
13. Determine the mass percent of each element in sulfuric acid.
14. Rubbing alcohol is an aqueous solution of isopropyl alcohol. Isopropyl alcohol has the formula
C3H7OH. Determine the mass percent of each element in isopropyl alcohol.
15. Determine the empirical formula from each of the following molecular formulas.
a. H2O2, hydrogen peroxide, a substance commonly diluted with water and used as a
b. C4H10, butane, commonly used in lighters
c. CCl4, carbon tetrachloride, an organic solvent
16. A 1.500 g sample of a compound containing only carbon and hydrogen is found to contain 1.198
g of carbon. Determine the empirical formula for this compound.
17. A 3.450 g sample of nitrogen reacts with 1.970 g of oxygen. Determine the empirical formula
for this compound.
18. When a 2.000 g sample of iron metal is heated in air, it reacts with oxygen o achieve a final
mass of 2.573g. Determine the empirical formula for this iron oxide.
19. A 4.550 g sample of cobalt reacts with 5.475 g chlorine to form a binary compound.
Determine the empirical formula for this compound.
20. Phosphoric acid is found in some soft drinks. A sample of phosphoric acid contains 0.3086 g
of hydrogen, 3.161 g of phosphorus, and 6.531 g of oxygen. Determine the empirical formula
for phosphoric acid.
21. Para-dichlorbenzene is often used in chemistry labs when studying melting points. A sample
of para-dichlorbenzene contains 5.657 g of carbon, 0.3165 g of hydrogen, and 5.566 g of
chlorine. Determine the empirical formula for this coumpound.
22. The simplest amino acid, glycine, has the following mass percents: 32.00% carbon, 6.714%
hydrogen, 42.63% oxygen, and 18.66% nitrogen. Determine the empirical formula for glycine.
23. A compound has been analyzed and found to have the following mass percent composition:
66.75% copper, 10.84% phosphorus, and 22.41% oxygen. Determine the empirical formula for this