SCH 4C1 Unit 2 Problem Set
Questions taken from Frank Mustoe et all, "Chemistry 11", McGraw-Hill Ryerson, 2001
1. A small pin contains 0.0178 mol of iron. How many atoms of iron are in the pin?
2. A sample contains 4.70 x 10-4 mol of gold. How many atoms of gold are in the
sample?
3. How many formula units are contained in 0.21 mol of Magnesium Nitrate
4. A litre of water contains 55.6 mol of water. How many molecules of water are in the
sample?
5. A typical bottle of nail polish remover contains 2.5 mol of ethyl acetate (C4H8O2).
a. How many molecules are in the bottle?
b. How many atoms are in the bottle?
c. How many carbon atoms are in the bottle?
6. Consider a 0.829 mol sample of sodium sulfate (Na2SO4)
a. How many formula units are in the sample?
b. How many sodium ions are in the sample?
7. A sample of Al2O3 contains 7.71 x 1024 molecules. How many moles is there?
8. A vat of cleaning solution contains 8.03 x 1026 molecules of NH4. How many moles
of ammonia are in the vat?
9. A sample of cyanic acid, HCN, contains 3.33 x 1022 atoms. How many moles of
cyanic acid are in the sample? HINT: Find the number of molecules of HCN first.
10. A sample of pure acetic acid, CH3COOH, contains 1.40 x 1023 carbon atoms. How
many moles of acetic acid are in the sample?
11. How many atoms make up the following compounds?
a. MgF2
b. Al(OH)3
c. Pb3(PO4)4
d. (NH4)2SO4
12. Find the Molar Mass of each compound
a. NH3
b. C6H12O6
c. K2Cr2O7
d. Fe2(SO4)3
e. SrSO4
13. Calculate the mass of each sample.
a. 103 moles of Mo
b. 1.32 x 104 moles of NaCl
c. 0.736 moles of MgO
d. 56.3 moles of H2O
14. How many moles of compound are in each sample?
a. 39.2 g of SiO2
b. 7.34 g of HNO2
c. 1.55 x 105 g of CF4
d. 8.11 x 10-3 g of C8H9I
15. Sodium Chloride can be used to melt snow. How many moles of sodium chloride are
in a 10 kg bag?
16. Octane, C8H18, is a principal ingredient in gasoline. Calculate the number of moles in
a 20.0 kg sample of octane.
17. Determine the mass of each sample.
a. 6.02 x 1024 formula units of ZnCl2
b. 7.38 x 1021 formula units of Pb3(PO4)2
c. 1.11 x 1023 molecules of C15H21N3O15
d. 1.20 x 1029 molecules of N2O5
18. Express the mass of a single atom of Ti in grams.
19. Vitamin B2, C12H20N4O6, is also called riboflavin. What is the mass, in grams, of a
single molecule of riboflavin?
20. Determine the number of molecules or formula units in each sample.
a. 10.0 g of water
b. 52.4 g of methanol, CH3OH
c. 23.5 g of disulphur dichloride, S2Cl2
d. 0.337 g of lead (II) phosphate, Pb3(PO4)2
21. How many atoms of hydrogen are in 5.3 x 104 molecules of sodium glutamate,
NaC5H8NO4?
22. How many molecules are in a 64.3 mg sample of tetraphosphorous decoxide,
P4O10?
23. a) How many formula units are in a 4.35 x 10-2 g sample of potassium chlorate,
KClO3?
b) How many oxygen atoms are in this sample?
24. A sample of a compound is analyzed and found to contain 0.90 g of calcium and
1.60 g of chlorine. The sample has a mass of 2.50 g. Find the percent composition
of the compound.
25. Find the percent composition of a pure substance that contains 7.22 g nickel, 2.53 g
phosphorous, and 5.25 g oxygen only.
26. A 650 mg sample of a compound is analyzed and found to contain 257 mg C and
50.4 mg H and an unknown element. What is the percentage composition?
27. A scientist analyses a 50.0 g sample and finds that it contains 13.3 g of potassium,
17.7 g of chromium, and another element. What is the mass percent of potassium in
this compound?
28. Calculate the mass percent of Nitrogen in each compound:
a. N2O
b. Sr(NO3)2
c. NH4NO3
d. HNO3
29. Sulfuric acid, H2SO4, is an important acid in laboratories and industries. Determine
the percent composition.
30. Potassium nitrate, KNO3, is used to make fireworks. What is the mass percent of
oxygen in potassium nitrate?
31. A compound consists of 17.6 % hydrogen and 82.4% nitrogen. Determine the
empirical formula of the compound.
32. Find the empirical formula of a compound that is 46.3% lithium and 53.7% oxygen.
33. What is the empirical formula of a compound that is 15.9% boron and 84.1%
fluorine?
34. Determine the empirical formula of a compound made up of 52.51% chlorine and
47.48% sulfur.
35. An oxide of chromium is made up of 68.4% chromium and 31.6% oxygen. What is
the empirical formula of this oxide?
36. Phosphorous reacts with oxygen to give a compound that is 43.7% phosphorous
and 56.4% oxygen. What is the empirical formula of the compound?
37. An inorganic salt is composed of 17.6% sodium, 39.7% chromium, and 42.8%
oxygen. What is the empirical formula of this salt?
38. The empirical Formula of butane is C2H5. In an experiment, the molar mass of
butane was determined to be 58 g/mol. What is the molecular formula?
39. Oxalic acid has the empirical formula CHO2. Its molar mass is 90 g/mol. What is the
molecular formula of oxalic acid?
40. The empirical formula of codeine is C18H21NO3. If the molar mass of codeine is 299
g/mol, what is its molecular formulas?
41. A 1.00 mol sample with a mass of 29.88 g contains 13.88 g Li and 16.00 g of O.
What is the molecular formula?
42. A compound’s molar mass is 240.28 g/mol. Its percent composition is 75.0% carbon,
5.05% hydrogen, and 20.0% oxygen. What is the compound’s molecular formula?
43. A fat used in making soap contains 76.5% carbon, 12.2% hydrogen and 11.3%
oxygen. Determine the molecular formula if the fat’s molar mass is 706.3 g/mol.
44. A substance contains 26.65% potassium, 35.33% chromium and 38.02% oxygen. Its
molar mass is 294.20 g/mol. Determine the molecular formula of the compound.
45. The percent composition of nicotine is 74.0% carbon, 8.7% hydrogen and 17.3%
nitrogen. Its molar mass is 162.26 g/mol. What is the molecular formula?
46. Compound X contains 69.9% carbon, 6.86% hydrogen and 23.3% oxygen.
Determine the empirical formula of compound X.
47. Consider the following reaction:
2H2(g) + O2(g)  2H2O(l)
a) Write the all the mole ratios
b) How many moles of O2 are required to react with 100 moles of H2?
c) How many moles of water are formed when 2478 moles of O2 react?
d) How many moles of H2 are required to react completely with 6.02 x 1023 moles of
O2?
48. Aluminum bromide can be prepared by reacting small pieces of aluminum foil with
liquid bromine at room temperature. The reaction is accompanied by flashes of red
light.
a) Write a balanced chemical equation of the above reaction.
b) How many moles of bromine are needed to produce 5.0 mol of aluminum bromide?
c) How many moles of aluminum are needed to react?
49. Ammonium sulfate, (NH4)2SO4, is used as a source of nitrogen in some fertilizers. It
reacts with sodium hydroxide to produce sodium sulfate, water and ammonia.
(NH4)2SO4(s) + 2NaOH(aq)  Na2SO4(aq) + 2NH3(g) + 2H2O(l)
What mass of sodium hydroxide is required to react completely with 15.4 g of
(NH4)2SO4?
50. Iron (III) oxide, also known as rust, can be removed from iron by reacting it with
hydrochloric acid to produce iron (III) chloride and water.
Fe2O3(s) + 6HCl(aq)  2FeCl3(aq) + 3H2O(g)
What mass of hydrogen chloride is required to react with 1.00 x 102 g of rust?
51. Iron reacts slowly with hydrochloric acid to produce iron (II) chloride and hydrogen
gas.
Fe(s) + 2HCl  FeCl2(aq) + H2(g)
What mass of HCl is required to react with 3.56 g of iron?
52. Dinitrogen pentoxide is a white solid. When heated it decomposes to produce
nitrogen dioxide and oxygen.
2N2O5(s)  4NO2(g) + O2(g)
How many grams of oxygen will be produced in this reaction when 2.34 g of NO 2 are
made?
53. Powdered zinc reacts rapidly with powdered sulfur in the following reaction:
8Zn(s) + S8(s)  8ZnS(s)
What mass of zinc sulfide is expected when 32.0 g of S8 reacts?
54. Aluminum carbide is a yellow powder that reacts with water to produce aluminum
hydroxide and methane.
Al4C3(s) + 12H2O(l)  4Al(OH)3(s) + 3CH4(g)
What mass of water is required to completely react with 25.0 g of aluminum carbide?
55. Nitrogen gas is produced in an automobile air bag. It is generated by the
decomposition of sodium azide:
2NaN3(s)  3N2(g) + 2Na(s)
To inflate the air bag on the driver’s side of a certain car, 1.72 x 1024 molecules of N2
are required. What mass of NaN3 is needed to produce this many molecules of N2?
56. The following balanced chemical equation shows the reaction of aluminum with
copper(II) chloride. If 0.25 g of aluminum reacts with 0.51 g of copper(II) chloride,
determine the limiting reactant.
2Al(s) + 3CuCl2(aq)  3Cu(s) + 2AlCl3(aq)
57. Hydrogen fluoride is a highly toxic gas. It is produced by the double displacement
reaction of calcium fluoride with concentrated sulfuric acid.
CaF2(s) + H2SO4(l)  2HF(g) + CaSO4(s)
Determine the limiting reactant when 10.0 g of CaF2 reacts with 15.5 g of H2SO4.
58. 3.76 g of zinc reacts with 8.93 x 1023 molecules of hydrogen chloride. Which reactant
is limiting?
59. Use the following equations to answer the questions below:
6ClO2(g) + 3H2O(l)  5HClO3(aq) + HCl(aq)
a) If 71.00 g of ClO2 is mixed with 19.00 g of water, what is the limiting reactant?
b) What mass of HClO3 is expected in part a)?
c) How many molecules of HCl are expected in part a)?
60. A student performs the following reaction with 1.23 g of MnI2 and 25.0 g of F2.
2MnI2(s) + 13F2(g)  2MnF3(s) + 4IF5(l)
What mass of MnF3 is expected?
61. A student mixes 5.3 g of barium chloride and 6.9 g of sodium sulphate. What mass
of barium sulphate is produced?
62. 20.0 g of HBrO3 is reacted with excess HBr.
HBrO3(aq) + 5HBr(aq)  3H2O(l) + 3Br2(aq)
a) What is the theoretical yield of Br2?
b) If 47.3 g of Br2 is produced, what is the percentage yield for this reaction?
63. Barium sulphate forms as a precipitate in the reaction between barium nitrate and
sodium sulphate. When 35.0 g of barium nitrate is reacted with excess sodium
sulphate, 29.8 g of precipitate is recovered.
a) Calculate the theoretical yield
b) Calculate the percentage yield
64. Yeast can act on sugar to produce alcohol in the following reaction:
C6H12O6(aq)  2C2H5OH(l)+ 2CO2(g)
If 223 g of alcohol are recovered after 1.63 kg of sugar react, what is the percentage
yield?
65. The following reaction proceeds with a 70% yield:
C6H6(l) + NNO3(aq)  C6H5NO2(l) + H2O(l)
Calculate the mass of C6H5NO2 expected if 12.8 g of C6H6 reacts with excess NNO3.
66. Marble is made primarily of calcium carbonate. When calcium carbonate reacts with
hydrogen chloride, it reacts to form calcium chloride, carbon dioxide and water. If
this reaction occurs with 81.5% yield, what mass of carbon dioxide will be collected if
15.7 g of calcium carbonate is added to sufficient hydrogen chloride?
67. 50.8 g of copper (II) chloride react in a single displacement reaction with 19.3 g of
magnesium metal. If the reaction has a 54.3% yield, how much copper metal will be
recovered?
22
1.
2.
3.
4.
5a)
5b)
5c)
6a)
6b)
7.
8.
9.
10.
11a)
11b)
1.07 X10 atoms
20
2.83 x 10 atoms
23
1.3 x 10 fu
25
3.35 x 10 molecules
24
1.5 x 10 molecules
25
2.1 x 10 atoms
24
6.0 x 10 atoms
23
4.99 x 10 fu
23
9.98 x 10 ions
12.8 mol
3
1.33 x 10 mol
0.0184 mol
0.116 mol
3 atoms
7 atoms
17c)
17d)
18.
19.
20a)
20b)
20c)
20d)
21.
22.
23a)
23b)
24.
25.
26.
11c)
11d)
12a)
12b)
12c)
12d)
23 atoms
15 atoms
17.04 g/mol
180.18 g/mol
294.20 g/mol
399.88 g/mol
27.
28a)
28b)
28c)
28d)
29.
12e)
13a)
13b)
13c)
13d)
14a)
14b)
14c)
14d)
15.
16.
17a)
17b)
183.68 g/mol
3
9.88 x 10 g
5
7.71 x 10 g
29.7 g
3
1.01 x 10 g
0.652 mol
0.156 mol
3
1.76 x 10 mol
-5
3.49 x 10 mol
2
1.7 x 10 mol
175 mol
3
1.36 x 10 g
9.95 g
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
Unit 2 Problem Set Answers
89.1 g
43.
7
2.15 x 10 g
44.
-23
7.95 x 10 g
45.
-22
5.25 x 10 g
46.
23
3.34 x 10 molecules
47b)
23
9.84 x 10 molecules
47c)
23
1.05 x 10 molecules
47d)
20
2.50 x 10 fu
48b)
5
4.2 x 10 atoms
48c)
20
1.36 x 10 molecules
49.
20
2.14 x 10 fu
50.
20
6.42 x 10 atoms
51
Ca=36%, Cl=64%
52.
Ni=48.1%,P=16.9%, O=35.0% 53.
C=39.5%, H=7.75%,
54.
Unknown=52.8%
26.6%
55.
63.65%
56.
13.24%
57.
35.00%
58.
22.23%
59a)
H=2.06%, S=32.69%,
59b)
O=65.25%
47.47%
59c)
NH3
60.
Li2O
61.
BF3
62a)
SCl
62b)
Cr2O3
63a)
P2O5
63b)
Na2Cr2O7
64.
C4H10
65.
C2H2O4
66.
C18H21NO3
67.
Li2O
C15H12O3
C45H85O5
K2Cr2O7
C10H14N2
C12H14O3
50 mol
4956 mol
24
1.20 x 10 mol
7.5 mol
5.0 mol
9.32 g
137 g
4.65 g
0.407 g
97.3 g
37.6 g
124 g
CuCl2
CaF2
Zn
ClO2
74.11 g
23
1.06 x 10
0.446 g
5.9 g
74.4 g
63.6%
31.3 g
95.2%
26.7%
14.1 g
5.63 g
13.0 g
molecules