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Chemistry I

Unit 6

Chemical Reactions and Equilibrium

Chapter 6

I. What are types of evidence that a chemical reaction has taken place?

II. Chemical equations are

a. Reactants vs. Products

b. Physical States

i. Solid

ii. Liquid

iii. Gas

iv. Aqueous

c. Practice Problems

III. Balancing Chemical Equations

a. Law of Conservation of Mass

b. Identities of compounds must never ________________________.

c. Use of Coefficients

d. See “How to Write and Balance Equations” on pg. 153

e. Practice Problems

Chapter 7

I. Predictions that a Reaction will Occur

a. Most Common Driving Forces

i.

ii.

iii.

iv.

II. Classification of Reactions

a. Acid/Base Reactions

b. REDOX Reactions

c. Double Displacement Reactions

d. Single Replacement Reactions

e. Combustion

f. Synthesis

g. Decomposition

h. Practice Problems

III. Precipitation Reactions are ________________________________

a. Strong electrolytes

b. Solubility Rules (see Table 7.1)

i. Soluble

ii. Insoluble

iii. Slightly soluble

c. Predicting Precipitates (see rules on pg. 172)

d. Practice Problems

IV. Aqueous Solutions

a. Molecular Equations

b. Ionic Equations

c. Spectator Ions

d. Net Ionic Equations

V. Acid/Base Reactions (see summary on pg. 180)

a. Practice Problems

VI. Oxidation-Reduction Reactions (REDOX)

a. Oxidations Numbers

b. Transfer of electrons

c. Reduction

d. Oxidation

e. Practice Problems

Chapter 17 Equilibrium

I. How exactly do reactions occur?

Collision Model –

II. Conditions that affect Reaction Rates

a. Concentration – The higher the concentration the faster the reaction occurs.

Why?

b. Temperature – Reactions speed up when the temperature increases.

Why?

c. Activation Energy –

d. Higher temp = Higher Speeds = More High-Energy collisions = More collisions that break bonds = Faster Reaction

e. Catalyst –

i. Example – Enzymes

III. Equilibrium

a. Balancing of two processes, which are opposite one another

b. Chemical Equilibrium –

i. Example: NO2

IV. Characteristic of an Equilibrium

a. An equilibrium is dynamic

b. Example : H2O(g) + CO(g)

V. Le Chatelier’s Principle

a. Definition:

b. Change in Concentration

i. If a reactant or product is added to an equilibrium, the system will shift away from the added component.

ii. If a reactant or product is taken from the equilibrium, the system will shift towards the removed component.

c. Change in Volume

i. Only applies to equilibriums involving gases.

ii. When pressure is increased the system will shift to the side with the smaller number of gas molecules.

d. Change in Temperature

i. If a reaction is exothermic, produces heat, the equilibrium will shift to the right if the temperature of the equilibrium is decreased.

1. Ex.

ii. If the reaction is endothermic, absorbs heat, the equilibrium will shift to the left if the temperature of the equilibrium is decreased.

1. Ex.

iii. Simply, treat temperature as a reactant or product.

Unit 6 Study Guide


1. All of the following are clues that a chemical reaction has taken place except

A) A color change occurs.

B) A solid forms.

C) The reactant is smaller.

D) Bubbles form.

E) A flame occurs.

2. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

Sn + NaOH Na2SnO2 + H2

A) 1

B) 2

C) 3

D) 4

E) 5

3. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

Na2S2O3 + I2 NaI + Na2S4O6

A) 1

B) 2

C) 3

D) 4

E) 6

4. You are asked to balance the chemical equation

H2 + O2 ® H2O. How many of the following ways are correct ways to balance this equation?

I. 2H2 + O2 ® 2H2O

II. H2 + O2 ® H2O

III. 4H2 + 2O2 ® 4H2O

IV. H2 + O2 ® H2O2

A) 0

B) 1

C) 2

D) 3

E) 4

5. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

Pb(NO3)2 + K2CO3 PbCO3 + KNO3

A) 5

B) 4

C) 3

D) 2

E) 1

6. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

Al + Fe3O4 Al2O3 + Fe

A) 1

B) 3

C) 6

D) 9

E) 12

7. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

CH3OH + O2 CO2 + H2O

A) 1

B) 2

C) 3

D) 4

E) 6

8. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

P4O10 + H2O H3PO4

A) 10

B) 6

C) 4

D) 2

E) 1

9. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

NO2 + H2O HNO3 + NO

A) 1

B) 2

C) 3

D) 4

E) 5

10. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

MnO2 + HCl MnCl2 + Cl2 + H2O

A) 5

B) 4

C) 3

D) 2

E) 1

11. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

PCl5 + H2O H3PO4 + HCl

A) 1

B) 2

C) 3

D) 4

E) 5

12. Balance the following equation in standard form and determine the sum of the coefficients.

LiAlH4(s) + AlCl3(s) ® AlH3(s) + LiCl(s)

A) 8

B) 9

C) 10

D) 11

E) 12

13. Which of the following statments is not true of balancing a chemical equation?

A) Subscripts in the reactants must be conserved in the products.

B) Coefficients are used to balance the atoms on both sides.

C) The law of conservation of matter must be followed.

D) Phases are often shown for each compound but are not critical to balancing an equation.

E) All of the above statements (a-d) are true.

14. Balance the following equation in standard form and determine the sum of the coefficients.

A) 3

B) 4

C) 6

D) 7

E) 14

16. Consider a reaction given by the equation aA + bB ® cC + dD. In this equation A, B, C, D represent chemicals, and a, b, c, d represent coefficients in the balanced equation. For a given reaction, how many values are there for the quantity “c/d”?

A) 1

B) 2

C) 3

D) 4

E) an infinite number

Use the following to answer questions 17-23:

When the following equations are balanced using the smallest possible integers, what is the number in front of the underlined substance in each case?

17. Pb(s) + AgNO3(aq) ® Pb(NO3)2 + Ag(s)

A) 1

B) 2

C) 4

D) 5

E) 6

18. S(s) + O2(g) ® SO2(g)

A) 1

B) 2

C) 3

D) 4

E) 5

19. N2(g) + O2(g) ® N2O3

A) 1

B) 2

C) 3

D) 4

E) 6

20. Al2O3(s) + H2SO4(aq) ® Al2(SO4)3(aq) + H2O(l)

A) 1

B) 2

C) 3

D) 6

E) 9

21. Sr(s) + P4(s) ® Sr3P2(s)

A) 2

B) 3

C) 6

D) 12

E) 18

22. C2H6(g) + O2(g) ® CO2(g) + H2O(g)

A) 4

B) 7

C) 8

D) 10

E) 14

23. Li(s) + O2(g) ® Li2O(s )

A) 1

B) 2

C) 3

D) 4

E) 5

24. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

KClO3 KCl + KClO4

A) 1

B) 2

C) 3

D) 4

E) 5

25. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

NBr3 + NaOH N2 + NaBr + HOBr

A) 1

B) 2

C) 3

D) 4

E) 5

26. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

C2H6 + O2 CO2 + H2O

A) 1

B) 2

C) 4

D) 6

E) 7

27. When the following equation is balanced using the smallest possible integers, what is the number in front of the substance in bold type?

SiCl4 + H2O SiO2 + HCl

A) 1

B) 2

C) 3

D) 4

E) 5

Use the following to answer questions 30-32:

When the following equations are balanced using the smallest possible integers, what is the number in front of the underlined substance in each case?

30. Sb(s) + O2(g) ® Sb2O5(s)

A) 1

B) 2

C) 4

D) 6

E) 12

31. C4H10(g) + O2(g) ® CO2(g) + H2O(g)

A) 2

B) 4

C) 6

D) 8

E) 10

32. CH3OH(l) + O2(g) ® CO2(g) + H2O(g)

A) 1

B) 2

C) 4

D) 6

E) 12

33. Which of the following statements about chemical reactions is false?

A) In balancing a chemical equation, all subscripts must be conserved.

B) When one coefficient is doubled, the rest of the coefficients in the balanced equation must also be doubled.

C) The subscripts in a balanced equation tell us the number of atoms in a molecule.

D) An individual coefficient in a balanced equation is meaningless.

E) The phases in a chemical reaction tell us the nature of the reactants and products.

34. When the equation Si(s) + HF(aq) ® SiF4(g) + H2(g) is balanced, what is the coefficient for HF?

A) 0

B) 1

C) 2

D) 3

E) 4

35. The factors that most commonly cause chemical reactions to occur are all the following except

A) formation of a solid

B) formation of a gas

C) formation of water

D) transfer of electrons

E) a decrease in temperature

36. A substance that, when dissolved in water, produces a solution that conducts electric current very efficiently is called

A) a strong electrolyte

B) a weak electrolyte

C) a strong ion

D) an electrical solute

E) none of these

37. When a precipitation reaction occurs, the ions that do not form the precipitate

A) evaporate

B) are cations only

C) form a second insoluble compound in the solution

D) are left dissolved in the solution

E) none of these

38. An aqueous solution of ammonium sulfate is allowed to react with an aqueous solution of lead(II) nitrate.

Identify the solid product in the balanced equation.

A) (NH4)2SO4

B) Pb(NO3)2

C) PbSO4

D) NH4NO3

E) There is no solid formed when the two solutions are mixed.

39. An aqueous solution of ammonium sulfate is allowed to react with an aqueous solution of lead (II) nitrate.

What is the coefficient of the solid in the balanced equation (in standard form)?

A) 1

B) 2

C) 3

D) 4

E) 6

40. An aqueous solution of ammonium sulfate is allowed to react with an aqueous solution of lead (II) nitrate.

The complete ionic equation contains which of the following species (when balanced in standard form)?

A)

B)

C)

D)

E)

41. An aqueous solution of ammonium sulfate is allowed to react with an aqueous solution of lead (II) nitrate.

The net ionic equation contains which of the following species (when balanced in standard form)?

A)

B)

C)

D)

E)

42. Which drawing best represents the mixing of aqueous calcium chloride with aqueous potassium sulfate when they are mixed in stoichiometric amounts (neither reactant is limiting)?

A)

B)

C)

D)

E)

43. An aqueous solution of sodium carbonate is reacted with an aqueous solution of calcium chloride.

Identify the solid in the balanced equation.

A) Na2CO3

B) CaCl2

C) NaCl

D) CaCO3

E) There is no solid formed when the two solutions are mixed.

44. An aqueous solution of sodium carbonate is reacted with an aqueous solution of calcium chloride.

What is the coefficient of the solid in the balanced equation (in standard form)?

A) 5

B) 4

C) 3

D) 2

E) 1

45. An aqueous solution of sodium carbonate is reacted with an aqueous solution of calcium chloride.

The complete ionic equation contains which of the following species (when balanced in standard form)?

A)

B)

C)

D)

E)

46. An aqueous solution of sodium carbonate is reacted with an aqueous solution of calcium chloride.

The net ionic equation contains which of the following species (when balanced in standard form)?

A)

B)

C)

D)

E)

47. The scientist who discovered the essential nature of acids through solution conductivity studies is

A) Priestley

B) Boyle

C) Einstein

D) Mendeleev

E) Arrhenius

49. An aqueous solution of potassium chloride is mixed with an aqueous solution of sodium nitrate.

Identify the solid in the balanced equation.

A) KCl

B) NaNO3

C) KNO3

D) NaCl

E) There is no solid formed when the two solutions are mixed.

50. An aqueous solution of potassium chloride is mixed with an aqueous solution of sodium nitrate.

The molecular equation contains which one of the following terms (when balanced in standard form)?

A) KCl(s)

B) KNO3(aq)

C) KNa(aq)

D) ClNO3(aq)

E) NaCl(s)

51. An aqueous solution of potassium chloride is mixed with an aqueous solution of sodium nitrate.

The complete ionic equation contains which of the following species (when balanced in standard form)?

A)

B)

C)

D)

E)

52. An aqueous solution of potassium chloride is mixed with an aqueous solution of sodium nitrate.

The net ionic equation contains which of the following species (when balanced in standard form)?

A)

B)

C)

D)

E) No net ionic equation exists for this reaction.

53. The reaction 2K(s) + Br2(l) ® 2KBr(s) is a(n) ______________ reaction.

A) precipitation

B) acid-base

C) oxidation-reduction

D) double-displacement

E) single-replacement

54. The reaction AgNO3(aq) + NaCl(aq) ® AgCl(s) + NaNO3(aq) is a(n) ______________ reaction.

A) precipitation

B) acid-base

C) oxidation-reduction

D) single-replacement

E) none of these

55. The equation 2C2H6 + 7O2 ® 4CO2 + 6H2O is an oxidation-reduction reaction. True or false, and why?

A) True; the carbon is oxidized, and the oxygen is reduced.

B) True; the carbon is reduced, and the oxygen is oxidized.

C) True; the carbon is oxidized, and the hydrogen is reduced.

D) True; the oxygen is reduced, and the hydrogen is oxidized.

E) False

56. The reaction HCl(aq) + KOH(aq) ® H2O(l) + KCl(aq) is a(n) ______________ reaction.

A) precipitation

B) acid-base

C) oxidation-reduction

D) single-replacement

E) none of these

57. How many electrons are transferred in the following oxidation-reduction reaction?

Zn(s) + 2AgNO3(aq) ® Zn(NO3)2(aq) + 2Ag(s)

A) 1

B) 2

C) 3

D) 4

E) 5

58. How many of the following are oxidation-reduction reactions?

I. reaction of a metal with a nonmetal

II. synthesis

III. combustion

IV. precipitation

V. decomposition

A) 1

B) 2

C) 3

D) 4

E) 5

59. In what type of reaction is water always a product?

A) precipitation

B) acid-base

C) oxidation

D) decomposition

E) synthesis

60. Classify the following reaction:

2Mg(s) + O2(g) ® 2MgO(s)

A) oxidation-reduction

B) combustion

C) synthesis

D) two of the above

E) a-c are all correct.

61. Classify the following reaction:

HNO3(aq) + KOH(aq) ® KNO3(aq) +H2O(l)

A) oxidation-reduction

B) combustion

C) precipitation

D) acid-base

E) two of the above

63. A reaction that involves a transfer of electrons is called a(n) ______________ reaction.

A) precipitation

B) acid-base

C) oxidation-reduction

D) double-displacement

E) none of these

64. Which of the following statements is not true?

A) When a metal reacts with a nonmetal, an ionic compound is formed.

B) A metal-nonmetal reaction can always be assumed to be an oxidation-reduction reaction.

C) Two nonmetals can undergo an oxidation-reduction reaction.

D) When two nonmetals react, the compound formed is ionic.

E) A metal-nonmetal reaction involves electron transfer.

65. The equation 2Al(s) + 2Br2(l) ® 2AlBr3(s) is a(n) ______________ reaction.

A) oxidation-reduction and decomposition

B) oxidation-reduction only

C) synthesis only

D) decomposition

E) combustion

66. The equation 2Ag2O(s) ® 4Ag(s) + O2(g) is a(n) ______________ reaction.

A) oxidation-reduction

B) synthesis

C) decomposition

D) combustion

E) two of these

67. CH4(g) + 2O2(g) ® CO2(g) + 2H2O(g)

A) oxidation-reduction

B) synthesis

C) decomposition

D) combustion

E) two of these


Name ____________________________________
Write a balanced chemical equation, using symbols and formulas, to represent each of the following chemical reactions:

1. iron + sulfur à iron (II) sulfide
2. zinc + copper (II) sulfate
à zinc sulfate + copper
3. silver nitrate
+ sodium bromide à sodium nitrate + silver bromide
4. potassium chlorate (heated)
à potassium chloride + oxygen
5.
methane (CH4) + oxygen à carbon dioxide + water
6. mercuric oxide (heated) à mercury + oxygen
7. potassium iodide + lead (II) nitrate à lead (II) iodide + potassium nitrate
8. aluminum
+ oxygen à aluminum oxide
9. magnesium chloride
+ ammonium nitrate à magnesium nitrate + ammonium chloride
10. iron (II) chloride
+ ammonium hydroxide à iron (II) hydroxide + ammonium chloride
11. ethane (C2H6) + oxygen
à carbon dioxide + water
12. iron (III) oxide + carbon à iron + carbon monoxide
13. iron
+ water à hydrogen + iron (III) oxide
14. iron (III) chloride + potassium hydroxide à potassium chloride + iron (III) hydroxide
15. aluminum
+ sulfuric acid à aluminum sulfate + hydrogen gas
16. sodium carbonate + calcium hydroxide à sodium hydroxide + calcium carbonate
17. carbon dioxide
+ water à carbonic acid (H2CO3)
18. phosphorus
+ oxygen à phosphorus pentoxide
19. sodium
+ water à sodium hydroxide + hydrogen
20. zinc
+ sulfuric acid (H2SO4)à zinc sulfate + hydrogen
21. aluminum sulfate
+ calcium hydroxide à aluminum hydroxide + calcium sulfate
22. calcium oxide
+ water à calcium hydroxide
23.
iron + cuprous nitrate à ferrous nitrate + copper
24. ferrous sulfide + HCl à hydrogen sulfide + ferrous chloride
25. potassium oxide + water à potassium hydroxide
26. ammonium sulfide
+ lead nitrate à ammonium nitrate + lead sulfide
27. mercuric hydroxide + phosphoric acid (H3PO4) à mercuric phosphate + water
28. potassium hydroxide + phosphoric acid à potassium phosphate + water
29. calcium chloride
+ nitric acid (HNO3) à calcium nitrate + hydrochloric acid
30. potassium carbonate
+ barium chloride à potassium chloride + barium carbonate
31. magnesium hydroxide
+ sulfuric acid à magnesium sulfate + water
33. sodium carbonate + hydrochloric acid (HCl) à sodium chloride + water + carbon dioxide
34. magnesium
+ nitric acid à magnesium nitrate + hydrogen
35. aluminum
+ ferric oxide à aluminum oxide + iron
36. potassium phosphate
+ magnesium chloride à magnesium phosphate + potassium chloride
37. ammonia (NH3)
+ oxygen à nitrogen + water
38. calcium carbonate (heated)
à calcium oxide + carbon dioxide
39. sodium chloride
+ sulfuric acid à sodium sulfate + hydrochloric acid (HCl)
40. fluorine
+ sodium hydroxide à sodium fluoride + oxygen + water
41. magnesium nitrate
+ calcium iodide à calcium nitrate + magnesium iodide
42. aluminum sulfate
+ ammonium bromide à aluminum bromide + ammonium sulfate
43. potassium fluoride
+ barium bromide à barium fluoride + potassium bromide
45. sodium nitrate (heated) à sodium nitrite + oxygen
46. lead hydroxide (heated)
à lead monoxide + water
47. ammonia
+ sulfuric acid (H2SO4)à ammonium sulfate
48. hydrochloric acid (HCl)
+ ammonia à ammonium chloride
49. cupric sulfate
+ iron à ferrous sulfate + copper

50. aluminum + hydrochloric acid (HCl) à aluminum chloride + hydrogen
51. carbon
+ oxygen à carbon dioxide
52. calcium bicarbonate
+ calcium hydroxide à calcium carbonate + water
53. hydrogen sulfide
+ oxygen àwater + sulfur
54. sodium hydroxide
+ calcium nitrate à sodium nitrate + calcium hydroxide
55. potassium iodide
+ chlorine à potassium chloride + iodine
56. sulfuric acid (H2SO4)
+ potassium hydroxide à potassium sulfate + water
57. carbon dioxide
+ carbon à carbon monoxide
58. calcium sulfate
+ sodium carbonate à calcium carbonate + sodium sulfate
60. aluminum + phosphoric acid (H3PO4) à hydrogen + aluminum phosphate
61. ammonium chloride
+ sodium nitrite à sodium chloride + nitrogen + water
63. lead nitrate (heated)
à lead monoxide + nitrogen dioxide + oxygen
64. mercurous oxide
+ oxygen à mercuric oxide
65. calcium oxide
+ magnesium chloride à magnesium oxide + calcium chloride
66. calcium
+ water à calcium hydroxide + hydrogen
67. chromium chloride + sulfuric acid (H2SO4) à chromium sulfate + hydrochloric acid
68. ferric nitrate
+ ammonium hydroxide à ferric hydroxide + ammonium nitrate
69. aluminum chloride
+ potassium phosphate à aluminum phosphate + potassium chloride
70. aluminum oxide
+ carbon + chlorine à carbon monoxide + aluminum chloride
71. cuprous oxide + hydrochloric acid (HCl) à cuprous chloride + water
72. magnesium bicarbonate
+ hydrochloric acid (HCl) à magnesium chloride + water + carbon dioxide
73. iron
+ oxygen à ferric oxide
74. silicon
+ water (heat) à silicon dioxide + hydrogen
75. ferric oxide
+ carbon monoxide à iron + carbon dioxide
76. calcium chloride
+ chromium nitrate à calcium nitrate + chromium chloride
77. zinc sulfide
+ oxygen à zinc oxide + sulfur dioxide
78. calcium phosphate
+ sulfuric acid (H2SO4) à calcium sulfate + phosphoric acid
79. ferric hydroxide (heated)
à ferric oxide + water
80. aluminum sulfate
+ sodium bicarbonate à aluminum hydroxide + sodium sulfate + carbon dioxide
81. calcium phosphate
+ silicon dioxide + carbon à phosphorus + calcium silicate + carbon monoxide
82. calcium oxide
+ sulfur dioxide à calcium sulfite

83. carbon dioxide + magnesium hydroxide à magnesium carbonate + water
84. calcium oxide
+ hydrochloric acid (HCl) à calcium chloride + water
85. calcium carbonate
+ silicon dioxide à calcium silicate + carbon dioxide
86. antimony
+ chlorine à antimony trichloride
87. magnesium nitride
+ water à magnesium hydroxide + ammonia
89. ammonium bicarbonate (heated)
+ ammonia à water + carbon dioxide
90. cupric oxide
+ ammonia à copper + water + nitrogen
92. hydrogen sulfide
+ cadmium nitrate à nitric acid + cadmium sulfide
93. barium bromide
+ sodium phosphate à barium phosphate + sodium bromide
94. aluminum chloride
+ ammonium fluoride à aluminum fluoride + ammonium chloride
95. silver nitrate
+ potassium sulfate à silver sulfate + potassium nitrate
96. bismuth nitrate
+ calcium iodide à bismuth iodide + calcium nitrate
97. aluminum chromate
+ ammonium sulfate à ammonium chromate + aluminum sulfate
98. zinc nitrate
+ ammonium bromide à zinc bromide + ammonium nitrate
99. bismuth nitrate
+ ammonium hydroxide à bismuth hydroxide + ammonium nitrate

Writing Chemical Reactions Additional Practice


46. Many ships are built with aluminum superstructures to save weight. Aluminum, however, burns in oxygen if there is a sufficiently hot ignition source, which has led to several tragedies at sea. Write the unbalanced chemical equation for the reaction of aluminum with oxygen, producing aluminum oxide as product.


47. Crude gun powders often contain a mixture of potassium nitrate and charcoal (carbon). When such a mixture is heated until reaction occurs, a solid residue of potassium carbonate is produced. The explosive force of the gunpowder comes from the fact that two gases are also produced (carbon monoxide and nitrogen), which increase in volume with great force and speed. Write the unbalanced chemical equation for the process.


48. The sugar sucrose, which is present in many fruits and vegetables, reacts in the presence of certain yeast enzymes to produce ethyl alcohol (ethanol) and carbon dioxide gas. Balance the following equation for this reaction of sucrose.
C12H22O11(aq) +H2O(l) — C2H5OH(aq) + CO2(g)

49. Methanol (methyl alcohol), CH3OH, is a very important industrial compound. Formerly, methanol was prepared by heating wood to high temperatures in the absence of air. The complex compounds present in wood are degraded by this process into a charcoal residue and a volatile portion that is rich in methanol. Today, methanol is instead synthesized from carbon monoxide and elemental hydrogen. Write the balanced chemical equation for this latter process.

50. The Hall process is an important method by which pure aluminum is prepared from its oxide (alumina, A12O3) by indirect reaction with graphite (carbon). Balance the following equation, which is a simplified representation of this process

Al2O3(s) + C(s) à Al(s) + CO2

51. Iron oxide ores, commonly a mixture of FeO and Fe2O3, are given the general formula Fe3O4. They yield elemental iron when heated to a very high temperature with either carbon monoxide or elemental hydrogen. Balance the following equations for these processes.
Fe3O4(s) + H2(g) —> Fe(s) + H2O(g)

Fe3O4(s) + CO(g) —> Fe(s) + CO2(g)

52. The elements of Group 1 all react with sulfur to form metal suflides. Write balanced chemical equations for the reactions of the Group 1 elements with sulfur.


53. When steel wool (iron) is heated in pure oxygen gas, the steel wool bursts into flame and a fine powder consisting of a mixture of iron oxides (FeO and Fe2O3) forms. Write separate unbalanced equations for the reaction of iron with oxygen to give each of these products.

54. One method of producing hydrogen peroxide to add barium peroxide to water. A precipitate of barium oxide forms, which may then be filtered off to leave a solution of hydrogen peroxide. Write the balanced chemical equation for this process.

55. When elemental boron, B, is burned in oxygen gas, the product is diboron trioxide. If the diboron trioxide is then reacted with a measured quantity of water, it reacts with the water to form what is commonly known as boric acid, B(OH)3. Write a balanced chemical equation for each of these processes.

56. A common experiment in introductory chemistry courses involves heating a weighed mixture of potassium chlorate, KClO3, and potassium chloride. Potassium chlorate decomposes when heated, producing potassium chloride and evolving oxygen gas. By measuring the volume of oxygen gas produced in this experiment, students can calculate the relative percentage of KClO3 and KCl in the original mixture. Write the balanced chemical equation for this process.

57. A common demonstration in chemistry courses involves industrial chemical adding a tiny speck of manganese (IV) oxide to a concentrated hydrogen peroxide, H2O2 solution. Hydrogen peroxide is unstable, and it decomposes quite spectacularly under these conditions to produce oxygen gas and steam (water vapor). Manganese (IV) oxide is a catalyst for the decomposition reaction of hydrogen peroxide and is not consumed in the reaction.. Write the balanced equation for the decomposition of hydrogen peroxide

58. The benches in many undergraduate chemistry laboratories are often covered by a film of white dust. This may be due to poor housekeeping, but the dust is usually ammonium chloride, produced by the gaseous reaction in the laboratory of hydrogen chloride and ammonia; most labs have aqueous solutions of these. Write the balanced chemical equation for the reaction of gaseous ammonia (NH3) and hydrogen chloride to form solid ammonium chloride.

59. Glass is a mixture of several compounds, but a major constituent of most glass is calcium silicate, CaSiO3. Glass can be etched by treatment with hydrogen fluoride: HF attacks the calcium silicate of the glass, producing gaseous and water-soluble products (which can be re move by washing the glass). For example, the volumetric glassware in chemistry laboratories is often graduated by using this process. Balance the following equation for the reaction of hydrogen fluoride with calcium silicate.

CaSiO3(s) + HF(g) à CaF2(aq) + SiF4(g) + H2O(1)

60. You decided to toast some English muffins, but left the muffins in the toaster too long so that they began to char. Is there evidence that a chemical reaction has taken place?

61. If you had a “sour stomach,” you might try an over-the-counter antacid tablet to relieve the problem. Can you ink of evidence that the action of such an antacid is a chemical reaction?

62. When iron wire is heated in the presence of sulfur, the iron soon begins to glow, and a chunky, blue-black mass of iron (II) sulfide is formed. Write the unbalanced chemical equation for this reaction.

63. When finely divided solid sodium is dropped into a flask containing chlorine gas, an explosion occurs and a fine powder of sodium chloride is deposited on the walls of the flask. Write the unbalanced chemical equation for this process.

64. If aqueous solutions of potassium chromate and barium chloride are mixed, a bright yellow solid (barium chromate) forms and settles out of the mixture, leaving potassium chloride in solution. Write a balanced chemical equation for this process.

65. When hydrogen sulfide, H2S, gas is bubbled through a solution of lead (II) nitrate, Pb(NO3)2, a black precipitate – lead (II) sulfide, PbS, forms, and nitric acid, HNO3, is produced. Write the unbalanced chemical equation for his reaction.

66. If an electric current is passed through aqueous solutions sodium chloride, sodium bromide, and sodium iodide, elemental halogens are produced at one electrode in each case, with hydrogen gas being evolved at the other electrode. If the liquid is then evaporated from the mixture, a residue of sodium hydroxide remains. Write balanced chemical equations for these electrolysis reactions.

67. When a strip of magnesium metal is heated in oxygen, into an intensely white flame and produces a finely powdered dust of magnesium oxide. Write the unbalanced chemical equation for this process.


68. When small amounts of acetylene gas are needed, a common process is to react calcium carbide with water. Acetylene gas is evolved rapidly from this combination even at room temperature, leaving a residue of calcium hydroxide. Write the balanced chemical equation for this process.

69. When solid red phosphorus, P4, is burned in air, the phosphorus combines with oxygen, producing a choking cloud of tetraphosphorus decoxide. Write the unbalanced chemical equation for this reaction.

70. When copper (II) oxide is boiled in an aqueous solution sulfuric acid, a strikingly blue solution of copper (II) sulfate forms along with additional water. Write the unbalanced chemical equation for this reaction.

71. When lead (II) sulfide is heated to high temperatures in a stream of pure oxygen gas, solid lead (II) oxide forms with the release of gaseous sulfur dioxide. Write the unbalanced chemical equation for this reaction.

72. When sodium sulfite is boiled with sulfur, the sulfite ions, SO32-, are converted to thiosulfate ions, S2O32-, resulting in a solution of sodium thiosulfate, Na2S2O3. Write the unbalanced chemical equation for this reaction.

73. Balance each of the following chemical equations.
a. Cl2(g) + KBr(aq)
à Br2(l) + KCl(aq)
b.
Cr(s) + O2(g)
à Cr2O3(s)
c. P4(s) + H2(g)
à PH3(g)
d. Al(s) + H2SO4(aq)
à Al2(SO4)3(aq) + H2(g)
e. PCl3(l) + H2O(l)
à H3PO3(aq) + HC1(aq)
f. SO(g) + O2(g)
à SO3(g)
g. C7H16(l) + O2(g)
à CO2(g) + H2O(g)
h. C2H6(g) + O2(g)
à CO2(g) + H2O(g)

74. Balance each of the following chemical equations.
a. ZnCl2(aq) + Na2CO3(aq)
à ZnCO3(s) + NaCl(aq)
b. Al(s) + H2SO4(aq)
à Al2(SO4)3(aq) + H2(g)
c. Mn(s) + S(s)
à MnS2(s)
d. C5H12(l) + O2 (g)
à CO2(g) + H2O(g)
e. H2O(l) + Br2(l)
à HBr(aq) + HOBr(aq)
f. MnS(s) + O2(g)
à MnO2(s) + SO2(g)
g.
PbC12(aq) + K2CrO4(aq)
à PbCrO4(s) + KC1(aq)
h. AgNO3(aq) + H2SO4(aq)
à Ag2SO4(s) + HNO3(aq)

75. Balance each of the following chemical equations.
a. SiCl4(1) + Mg(s)
à Si(s) + MgCl2(s)
b. NO(g) + Cl2(g)
à NOCl(g)
c. MnO2(s) + Al(s)
à Mn(s) + A12O3(s)
d.
Cr(s) + S8(s) à Cr2S3(s)
e. NH3(g) + F2(g)
à NH4P(s) + NF3g)
f.
AgS(s) + H2(g)
à Ag(s) + H2S(g)
g. 02(g)
à 03(g)
h. Na2SO3(aq) + S5(s)
à Na2S203(aq)

76. Balance each of the fo1lowg chemical equations.

a. Pb(NO3)2(aq) +K2CrO4(aq) à PbCrO4(s) + KNO3(aq)
b. BaCl2(aq) + Na2SO4(aq)
à BaSO4(s) + NaC1(aq)
c. CH3OH(l) +O2(g)
à CO2(g) + H2O(g)
d. Na2CO3(aq) + S(s) + SO2(g)
à CO2(g) + Na2S2O3(aq)
e. Cu(s) + H2SO4(aq)
à CuSO4(aq) + SO2(g) + H2O(l)
f. MnO2(s) + HCl(aq)
à MnCl2(aq) + Cl2(g) + H2O(l)
g. As2O3(s) + KI(aq) + HCl(aq)
à AsI3(s) + KCl(aq) + H2O(1)
h.
Na2S2O3(aq) + I2(aq) à Na2S406(aq) + NaI(aq)

Writing Chemical Reactions Additional Practice


46. Many ships are built with aluminum superstructures to save weight. Aluminum, however, burns in oxygen if there is a sufficiently hot ignition source, which has led to several tragedies at sea. Write the unbalanced chemical equation for the reaction of aluminum with oxygen, producing aluminum oxide as product.


47. Crude gun powders often contain a mixture of potassium nitrate and charcoal (carbon). When such a mixture is heated until reaction occurs, a solid residue of potassium carbonate is produced. The explosive force of the gunpowder comes from the fact that two gases are also produced (carbon monoxide and nitrogen), which increase in volume with great force and speed. Write the unbalanced chemical equation for the process.


48. The sugar sucrose, which is present in many fruits and vegetables, reacts in the presence of certain yeast enzymes to produce ethyl alcohol (ethanol) and carbon dioxide gas. Balance the following equation for this reaction of sucrose.
C12H22O11(aq) +H2O(l) — C2H5OH(aq) + CO2(g)

49. Methanol (methyl alcohol), CH3OH, is a very important industrial compound. Formerly, methanol was prepared by heating wood to high temperatures in the absence of air. The complex compounds present in wood are degraded by this process into a charcoal residue and a volatile portion that is rich in methanol. Today, methanol is instead synthesized from carbon monoxide and elemental hydrogen. Write the balanced chemical equation for this latter process.

50. The Hall process is an important method by which pure aluminum is prepared from its oxide (alumina, A12O3) by indirect reaction with graphite (carbon). Balance the following equation, which is a simplified representation of this process

Al2O3(s) + C(s) à Al(s) + CO2

51. Iron oxide ores, commonly a mixture of FeO and Fe2O3, are given the general formula Fe3O4. They yield elemental iron when heated to a very high temperature with either carbon monoxide or elemental hydrogen. Balance the following equations for these processes.
Fe3O4(s) + H2(g) —> Fe(s) + H2O(g)

Fe3O4(s) + CO(g) —> Fe(s) + CO2(g)

52. The elements of Group 1 all react with sulfur to form metal suflides. Write balanced chemical equations for the reactions of the Group 1 elements with sulfur.


53. When steel wool (iron) is heated in pure oxygen gas, the steel wool bursts into flame and a fine powder consisting of a mixture of iron oxides (FeO and Fe2O3) forms. Write separate unbalanced equations for the reaction of iron with oxygen to give each of these products.

54. One method of producing hydrogen peroxide to add barium peroxide to water. A precipitate of barium oxide forms, which may then be filtered off to leave a solution of hydrogen peroxide. Write the balanced chemical equation for this process.

55. When elemental boron, B, is burned in oxygen gas, the product is diboron trioxide. If the diboron trioxide is then reacted with a measured quantity of water, it reacts with the water to form what is commonly known as boric acid, B(OH)3. Write a balanced chemical equation for each of these processes.

56. A common experiment in introductory chemistry courses involves heating a weighed mixture of potassium chlorate, KClO3, and potassium chloride. Potassium chlorate decomposes when heated, producing potassium chloride and evolving oxygen gas. By measuring the volume of oxygen gas produced in this experiment, students can calculate the relative percentage of KClO3 and KCl in the original mixture. Write the balanced chemical equation for this process.

57. A common demonstration in chemistry courses involves industrial chemical adding a tiny speck of manganese (IV) oxide to a concentrated hydrogen peroxide, H2O2 solution. Hydrogen peroxide is unstable, and it decomposes quite spectacularly under these conditions to produce oxygen gas and steam (water vapor). Manganese (IV) oxide is a catalyst for the decomposition reaction of hydrogen peroxide and is not consumed in the reaction.. Write the balanced equation for the decomposition of hydrogen peroxide

58. The benches in many undergraduate chemistry laboratories are often covered by a film of white dust. This may be due to poor housekeeping, but the dust is usually ammonium chloride, produced by the gaseous reaction in the laboratory of hydrogen chloride and ammonia; most labs have aqueous solutions of these. Write the balanced chemical equation for the reaction of gaseous ammonia (NH3) and hydrogen chloride to form solid ammonium chloride.

59. Glass is a mixture of several compounds, but a major constituent of most glass is calcium silicate, CaSiO3. Glass can be etched by treatment with hydrogen fluoride: HF attacks the calcium silicate of the glass, producing gaseous and water-soluble products (which can be re move by washing the glass). For example, the volumetric glassware in chemistry laboratories is often graduated by using this process. Balance the following equation for the reaction of hydrogen fluoride with calcium silicate.

CaSiO3(s) + HF(g) à CaF2(aq) + SiF4(g) + H2O(1)

60. You decided to toast some English muffins, but left the muffins in the toaster too long so that they began to char. Is there evidence that a chemical reaction has taken place?

61. If you had a “sour stomach,” you might try an over-the-counter antacid tablet to relieve the problem. Can you ink of evidence that the action of such an antacid is a chemical reaction?

62. When iron wire is heated in the presence of sulfur, the iron soon begins to glow, and a chunky, blue-black mass of iron (II) sulfide is formed. Write the unbalanced chemical equation for this reaction.

63. When finely divided solid sodium is dropped into a flask containing chlorine gas, an explosion occurs and a fine powder of sodium chloride is deposited on the walls of the flask. Write the unbalanced chemical equation for this process.

64. If aqueous solutions of potassium chromate and barium chloride are mixed, a bright yellow solid (barium chromate) forms and settles out of the mixture, leaving potassium chloride in solution. Write a balanced chemical equation for this process.

65. When hydrogen sulfide, H2S, gas is bubbled through a solution of lead (II) nitrate, Pb(NO3)2, a black precipitate – lead (II) sulfide, PbS, forms, and nitric acid, HNO3, is produced. Write the unbalanced chemical equation for his reaction.

66. If an electric current is passed through aqueous solutions sodium chloride, sodium bromide, and sodium iodide, elemental halogens are produced at one electrode in each case, with hydrogen gas being evolved at the other electrode. If the liquid is then evaporated from the mixture, a residue of sodium hydroxide remains. Write balanced chemical equations for these electrolysis reactions.

67. When a strip of magnesium metal is heated in oxygen, into an intensely white flame and produces a finely powdered dust of magnesium oxide. Write the unbalanced chemical equation for this process.


68. When small amounts of acetylene gas are needed, a common process is to react calcium carbide with water. Acetylene gas is evolved rapidly from this combination even at room temperature, leaving a residue of calcium hydroxide. Write the balanced chemical equation for this process.

69. When solid red phosphorus, P4, is burned in air, the phosphorus combines with oxygen, producing a choking cloud of tetraphosphorus decoxide. Write the unbalanced chemical equation for this reaction.

70. When copper (II) oxide is boiled in an aqueous solution sulfuric acid, a strikingly blue solution of copper (II) sulfate forms along with additional water. Write the unbalanced chemical equation for this reaction.

71. When lead (II) sulfide is heated to high temperatures in a stream of pure oxygen gas, solid lead (II) oxide forms with the release of gaseous sulfur dioxide. Write the unbalanced chemical equation for this reaction.

72. When sodium sulfite is boiled with sulfur, the sulfite ions, SO32-, are converted to thiosulfate ions, S2O32-, resulting in a solution of sodium thiosulfate, Na2S2O3. Write the unbalanced chemical equation for this reaction.

73. Balance each of the following chemical equations.
a. Cl2(g) + KBr(aq)
à Br2(l) + KCl(aq)
b.
Cr(s) + O2(g)
à Cr2O3(s)
c. P4(s) + H2(g)
à PH3(g)
d. Al(s) + H2SO4(aq)
à Al2(SO4)3(aq) + H2(g)
e. PCl3(l) + H2O(l)
à H3PO3(aq) + HC1(aq)
f. SO(g) + O2(g)
à SO3(g)
g. C7H16(l) + O2(g)
à CO2(g) + H2O(g)
h. C2H6(g) + O2(g)
à CO2(g) + H2O(g)

74. Balance each of the following chemical equations.
a. ZnCl2(aq) + Na2CO3(aq)
à ZnCO3(s) + NaCl(aq)
b. Al(s) + H2SO4(aq)
à Al2(SO4)3(aq) + H2(g)
c. Mn(s) + S(s)
à MnS2(s)
d. C5H12(l) + O2 (g)
à CO2(g) + H2O(g)
e. H2O(l) + Br2(l)
à HBr(aq) + HOBr(aq)
f. MnS(s) + O2(g)
à MnO2(s) + SO2(g)
g.
PbC12(aq) + K2CrO4(aq)
à PbCrO4(s) + KC1(aq)
h. AgNO3(aq) + H2SO4(aq)
à Ag2SO4(s) + HNO3(aq)

75. Balance each of the following chemical equations.
a. SiCl4(1) + Mg(s)
à Si(s) + MgCl2(s)
b. NO(g) + Cl2(g)
à NOCl(g)
c. MnO2(s) + Al(s)
à Mn(s) + A12O3(s)
d.
Cr(s) + S8(s) à Cr2S3(s)
e. NH3(g) + F2(g)
à NH4P(s) + NF3g)
f.
AgS(s) + H2(g)
à Ag(s) + H2S(g)
g. 02(g)
à 03(g)
h. Na2SO3(aq) + S5(s)
à Na2S203(aq)

76. Balance each of the fo1lowg chemical equations.

a. Pb(NO3)2(aq) +K2CrO4(aq) à PbCrO4(s) + KNO3(aq)
b. BaCl2(aq) + Na2SO4(aq)
à BaSO4(s) + NaC1(aq)
c. CH3OH(l) +O2(g)
à CO2(g) + H2O(g)
d. Na2CO3(aq) + S(s) + SO2(g)
à CO2(g) + Na2S2O3(aq)
e. Cu(s) + H2SO4(aq)
à CuSO4(aq) + SO2(g) + H2O(l)
f. MnO2(s) + HCl(aq)
à MnCl2(aq) + Cl2(g) + H2O(l)
g. As2O3(s) + KI(aq) + HCl(aq)
à AsI3(s) + KCl(aq) + H2O(1)
h.
Na2S2O3(aq) + I2(aq) à Na2S406(aq) + NaI(aq)