Chemistry Problem Solving 10.1 Measuring Matter
1. Calculate the number of molecules in 15.7 mol carbon dioxide.
2. Calculate the number of molecules in 0.0544 mol H2O.
3. Calculate the number of moles in 9.221023 atom iron.
4. Calculate the number of moles of sucrose in a sample that contains 2.051022 sucrose molecules.
5. A student uses 0.0850 mol copper sulfate to carry out a reaction. If the reaction uses up 0.0832 mol copper sulfate, how
many formula units are left unreacted?
Chemistry Problem Solving 10.2 Mass and the Mole
6. Calculate the mass of 6.89 mol antimony.
7. A chemist needs 0.0700 mol selenium for a reaction. What mass of selenium should the chemist use?
8. A sample of sulfur has a mass of 223 g. How many moles of sulfur are in the sample?
9.A tank of compressed helium contains 50.0 g helium. How many moles of helium are in the tank?
10. A nickel coin is 25.0% nickel and 75.0% copper. If a nickel has a mass of 5.00 g, how many moles of Ni are in a nickel
coin?
11. Calculate the number of atoms in 2.00 g of platinum.
12. How many sulfur atoms are in a metric ton (1.00×106 g) of sulfur?
13. How many grams of mercury are in 1.191023 atoms of mercury?
14. What is the mass in grams of 3.011019 atoms of iodine?
15. The EPA limit for lead in the water supply is 15 parts per billion by mass. Calculate the number of lead ions present in
1.00 kg of water that is at the EPA limit for lead.
Chemistry Problem Solving 10.3 Moles of Compounds
16. Calculate the number of moles in 17.2 g of benzene (C6H6).
17. Calculate the number of moles in 350.0 g of potassium chlorate (KClO3).
18. Determine the mass of 0.187 mol of tin(II) sulfate (SnSO4).
19. A chemist needs 1.35 mol of ammonium dichromate for a reaction. The formula for this substance is (NH4)2Cr2O7. What
mass of ammonium dichromate should the chemist measure out?
20. A student needs 0.200 mol each of zinc metal and copper(II) nitrate (Cu(NO 3)2) for an experiment. What mass of each
should the student obtain?
Chemistry Problem Solving 10.4 Empirical and Molecular Formulas
21. Calculate the percent composition of aluminum oxide (Al 2O3).
22. Determine the percent composition of magnesium nitrate, which has the formula Mg(NO 3)2.
23. Calculate the percent oxygen in potassium chlorate (KClO3).
24. Calculate the percent nitrogen in ammonium hexacyanoiron(II), which has the formula (NH 4)4Fe(CN)6.
25. Acetylene gas has the molecular formula C2H2. How does the percent composition of acetylene compare with that of
benzene (C6H6)?
26. The composition of acetic acid is 40.00% carbon, 6.71% hydrogen, and 53.29% oxygen. Calculate the empirical formula
for acetic acid.
27. An unknown compound is analyzed and found to be composed of 14.79% nitrogen, 50.68% oxygen, and 34.53% zinc.
Calculate the empirical formula for the compound.
28. Calculate the empirical formula for a compound whose analysis is 74.97% aluminum and 25.03% carbon.
29. The composition of ascorbic acid (vitamin C) is 40.92% carbon, 4.58% hydrogen, and 54.50% oxygen. What is the
empirical formula for vitamin C?
30. Ricinine is one of the poisonous compounds found in the castor plant. The composition of ricinine is 58.54% carbon,
4.91% hydrogen, 17.06% nitrogen, and 19.49% oxygen. Ricinine’s molar mass is 164.16 g/mol. Determine its molecular
formula.
31. The compound borazine consists of 40.29% boron, 7.51% hydrogen, and 52.20% nitrogen, and its molar mass is 80.50
g/mol. Calculate the molecular formula for borazine.
32. The composition of silver oxalate is 71.02% silver, 7.91% carbon, and 21.07% oxygen. If the molar mass of silver oxalate
is 303.8 g/mol, what is its molecular formula?
33. A compound of phosphorus and sulfur contains 27.87% phosphorus and 72.13% sulfur. The molar mass of the compound
is 222.3 g/mol. Calculate its molecular formula.
34. Triethylenemelamine is used in the plastics industry and as an anticancer drug. Its analysis is 52.93% carbon, 5.92%
hydrogen, and 41.15% nitrogen. The molar mass of triethylenemelamine is 204.2 g/mol. Determine its molecular
formula.
Chemistry Problem Solving 10.5 Hydrates
35. Cerium(III) iodide (CeI3) occurs as a hydrate with the composition 76.3% CeI3 and 23.7% H2O. Calculate the formula for
the hydrate.
36. Cobalt(II) nitrate (Co(NO3)2) is used in ceramic glazes and produces a blue color when the ceramic is fired. This
compound exists as a hydrate whose composition is 37.1% water and 62.9% Co(NO3)2 by mass. Write the molecular
formula for this hydrate.
37. Lead(II) acetate (Pb(C2H3O2)2) exists as a crystalline hydrate that is 14.25% water by mass. What is the molecular
formula for this hydrate?
38. A 17.44-g sample of a hydrate of zinc sulfate (ZnSO4) is heated strongly in a crucible to drive off all water of hydration.
After heating, the sample has a mass of 9.79 g. Calculate the molecular formula for this hydrate. (Hint: The mass lost
represents water. First determine the moles of water lost from the hydrate.)
Chemistry Problem Solving 10 Review
39. Explain in detail how it is possible to count atoms, ions, formula units, and molecules by measuring mass.
40. Why must a chemist be able to count particles of matter?
41. How is the molar mass of a compound related to the atomic masses of the atoms in the compound?
42. The atomic mass of nitrogen is 14.007 amu. What is the mass in grams of a mole of N2 molecules?
43. An analysis of silicon dioxide (SiO2) found in beach sand in California shows that it is 46.74% silicon and 53.26% oxygen.
Can you assume that silicon dioxide found in a quartz rock in Michigan will have the same analysis? Explain your answer.
44. The empirical formula for a certain compound is found to be C2H4O. From this information, what can you predict about
the molecular formula for the compound?
45. The formula for magnesium bromide hexahydrate is MgBr2 • 6H2O. This compound could be represented by the formula
MgBr2H12O6. Explain why this formula is almost never used.