Chapter 3
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Textbook Problems:
Chapter 3 Page 134: 5, 7, 21, 27, 33, 35, 39, 53, 57, 61, 75, 79, 85, 95, 107, 117
Answers in back of textbook, page ANS-15
Additional Problems:
1. How many carbon atoms are there in a 1.00 g sample of stearic acid (C18H36O2)?
2. What is the mass percentage of each element in stearic acid?
3. A scientist has equal masses of C6H12 and C8H16. Which sample has more carbon atoms?
a. C6H12
b. C8H16
c. The number of carbon atoms in each sample is the same
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4. A scientist measures out 18.78 g of ethanol (C2H5OH). How many moles of ethanol is this?
5. Balance the following chemical equation:
HCl(aq) +
O2(g) →
H2O(l) +
Cl2(g)
6. Balance the following chemical equation:
C6H14(g) +
O2(g) →
CO2(g) +
H2O(l)
7. Aluminum metal reacts with chromium(III) oxide to form aluminum oxide and chromium
metal. If 38.64 g of chromium(III) oxide reacts with an excess of aluminum then what mass (in
grams) of chromium metal will form? The reaction goes to completion.
8. A 6.35 g sample of solid calcium carbonate is added to an excess of hydrochloric acid and
produces aqueous calcium chloride, liquid water, and carbon dioxide gas. Calculate the mass of
carbon dioxide produced AND the minimum number of moles of hydrochloric acid needed. The
reaction goes to completion.
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9. Consider the combustion of liquid heptane (C7H16(ℓ)). If 1.00 g of liquid heptane is combusted
in an excess of oxygen, calculate the mass of carbon dioxide and water that will be produced.
The reaction goes to completion.
10. A compound is 67.97% by mass vanadium and 32.03% by mass oxygen. What is its
empirical formula?
11. A hydrocarbon is combusted in an excess of air. 15.32 grams of carbon dioxide and 7.32
grams of water are produced. What is the empirical formula of the compound?
12. 11.00 grams of an organic compound containing only carbon, hydrogen, and oxygen is
combusted in an excess of air. 23.31 grams of carbon dioxide and 3.58 grams of water are
produced. What is the empirical formula of the compound?
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13. A compound's M+ peak has a value of 228 amu. Which of the following are possibilities for
the compound's empirical formula? Select all valid choices.
a. C6H10O2
b. C15H20N2
c. C3H5O
d. C15H20NO
14. Combustion analysis of 5.000 g of an organic molecule containing only carbon, hydrogen,
and nitrogen yields of 9.03 g of carbon dioxide and of 5.54 g of water. Determine the empirical
and molecular formula of the unknown: the mass spectrum is provided below.
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15. Consider the following reaction between niobium and iodine:
3 Nb(s) + 4 I2 (s) → Nb3I8(s)
When 25.00 grams of niobium is mixed with 95.00 grams of iodine the percent yield for
the product is 82.09%. What mass of product (in grams) formed?
16. Consider the reaction between iron(III) oxide and carbon monoxide:
Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g)
129g of iron(III) oxide reacts with 54.3 g of carbon monoxide. Calculate the final masses
of all reactants and products if the reaction goes to completion.
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17. Copper metal will react with oxygen gas to form copper (II) oxide.
a. Calculate the mass of copper (II) oxide that will form if 1.000 g of copper metal is
completely converted into copper (II) oxide.
b. A 1.000 g sample of copper metal is heated in a crucible and after 15 minutes the mass of
the crucible contents is 1.111 g. Calculate the mass of copper (II) oxide that was
produced.
18. When 2.95 g of Na2CO3•nH2O reacts with an excess of acid 0.662 g of carbon dioxide is
formed. What is the value of n? Round to the nearest whole number.
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Answers:
1. 3.81*1022 C atoms
2. 75.99% C, 12.76% H, 11.25% O
3. c
4. 0.4076 mol ethanol
5. 4,1,2,2
6. 2,19,12,14
7. 26.44 g Cr
8. 2.79 g CO2 , 0.127 mol HCl
9. 3.07 g CO2 ,1.44 g H2O
10.V2O3
11.C3H7
12.C4H3O2
13.b & c
14.C3H9N2 , C6H18N4
15.95.28 g Nb3I8(s)
16.Fe2O3(s) = 25.7 g
CO(g) = 0 g
Fe(s) = 72.3 g
CO2(g) = 85.4 g
17.1.252 g CuO, 0.552 g CuO
18.n= 5
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