300 Chemistry Problems
Molar Relationships
Do on separate paper or in your notebook
1. Determine the molar mass of each of the following compounds:
a. KMnO4
b. KCl
c. Na2SO4
d. Mg3(PO4)2
e. H2CO3
f. Hg2Cr2O7
g. Ba(ClO3)2
h. CuSO4 · 5 H2O
i. Calcium nitrate
j. Aluminum sulfate
k. Ammonium phosphate
l. Zinc acetate dihydrate
m. Iron(III) sulfite
n. Ammonium acetate
2. Determine the percent composition of all elements in each of the following
compounds:
a. (NH4)2SO3
b. Al(C2H3O2)3
c. NaBr
d. Cu(OH)2
e. MgCO3
f. Fe3(PO4)2
g. Be3N2
h. Potassium cyanide
i. Manganese(III) nitrate
j. Lithium phosphide
k. Nickel(III) sulfate
l. Silver nitrate
m. Copper(I) chloride
n. Water
o. Calcium phosphate
p. Ammonium phosphate
3. How many grams of oxygen can be produced from 100. g of KClO3?
4. How many grams of iron can be recovered from 25.0 g of Fe2O3?
5. What mass of silver can be produced from 125 g of Ag2S?
6. What percentage of water is found in CuSO4·5H2O?
7. What percentage of water is found in Na2S·9H2O?
8. A 5.00 g sample of a hydrate of BaCl2 was heated, and only 4.35 g of the
anhydrous salt remained. What percentage of water was in the hydrate?
9. A 3.24 g sample of Na2CO3·H2O is heated to constant mass. How much (g)
anhydrous salt remains?
10. How many molecules are in the quantities below?
a. 0.732 moles
b. 2.0 moles
c. 1.776 moles
d. 15.89 moles
11. How many moles are in the number of molecules below?
a. 1.56x1020 molecules
b. 1.204x1024 molecules
c. 3.425x1026 molecules
d. 7.51x1019 molecules
12. How many moles are in the quantities below?
a. 25.0 g of Na2SO4
b. 125 g of HCl
c. 105.98 g of KCl
d. 72.5 g of KMnO4
e. 3.12 g of CuSO4·5H2O
13. What is the mass of each of the following?
a. 2.54 moles of NaCl
b. 0.500 moles of H2SO4
c. 1.706 moles of KMnO4
d. 0.255 moles of KCl
e. 3.211 moles of CuSO4·5H2O
14. How many formula units are in there in 24.5 g of AlF3?
15. How many formula units are there in 454 g of K2SO4?
16. How many grams are there in 2.32x1024 atoms of iron?
17. How many grams are there in 7.34x1023 formula units of silver nitrate?
18. How many grams are there in 5.67x1020 molecules of carbon dioxide?
19. How many atoms are there in 5.67x1020 molecules of carbon dioxide?
20. How many silver ions are there in 7.34x1023 formula units of silver nitrate?
21. How many sodium ions are there in 454 g of Na2SO4?
22. How many moles are in 15.64 g of carbon?
23. How many grams are in 2.4 moles of oxygen (careful!)?
24. How many moles are in 68.00 g of copper(II) chloride?
25. How many formula units are in 68.00 g of copper(II) chloride?
26. How many chloride ions are in 68.00 g of copper(II) chloride?
27. How many copper ions are in 68.00 g of copper(II) chloride?
28. How many grams are in 1.34 moles of potassium sulfide?
29. How many molecules are in 69.37 g of sulfur dioxide?
30. How many atoms are in 62.17 g of sulfur dioxide?
31. How many moles are in 1.23x1025 molecules of sodium chloride?
32. How many atoms are in 5.00 g of gold?
33. What is the empirical formula of the compounds with the percents composition
shown below?
a. 75% carbon, 25% hydrogen
b. 52.7% potassium, 47.3% chlorine
c. 22.1% aluminum, 25.4% phosphorous, 52.5% oxygen
d. 13% magnesium, 87% bromine
e. 32.4% sodium, 22.5% sulfur, 45.1% oxygen
f. 25.3% copper, 12.9% sulfur, 25.7% oxygen, 36.1% water (Careful: This
one is a hydrate!)
34. The empirical formula of a compound is NO2. Its molecular mass is 92 g/mol.
What is its molecular formula?
35. The empirical formula of a compound is CH2. Its molecular mass is 70 g/mol.
What is its molecular formula?
36. The empirical formula of a compound is C2OH4, and its molar mass is 88 g/mol.
What is its molecular formula?
37. The empirical formula of a compound is C4H4O, and its molar mass is 136 g/mol.
What is its molecular formula?
38. The empirical formula of a compound is CFBrO, and its molar mass is 254.7
g/mol. What is its molecular formula?
39. The empirical formula of a compound is C2H8N, and its molar mass is 46 g/mol.
What is its molecular formula?
40. A compound is found to be 40.0% carbon 6.70% hydrogen, and 53.5% oxygen.
Its molecular mass is 60.0 g/mol. What is its molecular formula?
41. A compound is found to be 64.9% carbon 13.5% hydrogen, and 21.6% oxygen.
Its molecular mass is 74.0 g/mol. What is its molecular formula?
42. A compound is found to be 54.5% carbon 9.10% hydrogen, and 36.4% oxygen.
Its molecular mass is 88.0 g/mol. What is its molecular formula?
43. Find the empirical and molecular formulas of a compound containing 65.5%
carbon, 5.50% hydrogen, and 29.0% oxygen and having a molar mass of 110
g/mol.
44. Find the empirical and molecular formulas of a compound containing 18.7%
lithium, 16.3% carbon, and 65.0% oxygen and having a molar mass of 73.8
g/mol.
For additional practice:
Relevant sections in textbook are 6.3-6.8
Practice problems are p. 188 (14-16, 19), p. 189 (20-29, 33, 34), p. 190 (35, 37, 39, 4250)