Chemistry Chapter 8 Chemical Equations

1
Chemistry Chapter 8 Chemical Equations

• Balancing Formula Equations

2
What is a Chemical Reaction?

• A chemical reaction occurs when two or more
  substances are changed into different substances.

3
What is a Chemical Equation?A chemical
equation represents, with symbols and formulas,
the identities and relative molecular or molar
amounts of the reactants and products in a
chemical reaction.
4
Indications of a Chemical Reaction

• Evolution of energy as heat and light.
• Production of a gas.
• Formation of a precipitate.
• Color change.

5
Characteristics of Chemical Equations

• The equation must represent known facts.
• The equation MUST contain the correct formulas
  for the reactants and products.
• The Law of Conservation of Mass must be
  satisfied. We can use coefficients to satisfy
  this law.
• coefficients- a small whole number that
  appears in front of a formula in a chemical
  equation

6
Word Formula Equations

• word equation- an equation in which the
  reactants and products of a reaction are
  represented by words
• formula equation- represents the reactants and
  products of a chemical reaction by their symbols
  formulas
• balanced formula equation- uses coefficients to
  allow conservation of mass

7
Examples of the Types of Equations

• word equation-
• iron II phosphate reacts with aluminum nitrate
  to produce iron II nitrate and aluminum phosphate
• formula equation-
• Fe3(PO4)2 Al(NO3)3 ? Fe(NO3)2 AlPO4
• balanced formula equation-
• Fe3(PO4)2 2 Al(NO3)3 ? 3 Fe(NO3)2 2 AlPO4

8
Symbols Used in Chemical Equations

• ? yields
• (s) solid
• (l) liquid
• (aq) aqueous
• (g) gas

9
Diatomic Elements

• There are seven common elements that are called
  the diatomic elements. Whenever they are pure
  elements and appear alone (NOT in a compound) in
  an equation, their symbol contains two atoms
  rather than one. They include
• hydrogen (H2) oxygen (O2) nitrogen
  (N2) fluorine (F2) chlorine
  (Cl2) bromine (Br2)
• iodine (I2)
• A simple mnemonic is halogens HON.

10
Practice Problems

• Do practice problems 1, 2, 3 on page 268 of
  the textbook.

11
Practice Problem 1 page 268

• 1a) Ca (s) S (s) ? CaS (s) already balanced
• 1b) H2 (g) F2 (g) ? HF (g)
• H2 (g) F2 (g) ? 2 HF (g) balanced
• 1c) Al (S) ZnCl2 (aq) ? Zn (s) AlCl3 (aq)
• 2 Al(S) 3 ZnCl2 (aq) ? 3 Zn(s) 2
  AlCl3(aq)

12
Practice Problem 2 page 268

• 2a) CS2(l) O2(g) ? CO2(g) SO2(g)
• liquid carbon disulfide reacts with oxygen gas
  to produce carbon dioxide gas and sulfur dioxide
  gas
• 2b) NaCl(aq) AgNO3(aq) ? NaNO3(aq) AgCl(s)
• aqueous sodium chloride reacts with aqueous
  silver nitrate to yield aqueous sodium nitrate
  and solid silver chloride

13
Practice problem 3 page 268

• N2H4 O2 ? N2 (g) H2O
• N2H4 O2 ? N2 (g) 2 H2O

14
Significance of a Chemical Equation

1. The coefficients of a chemical reaction indicate
   relative, not absolute, amounts of reactants and
   products.
2. The relative masses of the reactants and products
   of a chemical reaction can be determined from the
   reactions coefficients.
3. The reverse reaction for a chemical equation has
   the same relative amounts of substances as the
   forward reaction.

15
Rules for Balancing Chemical Equations

• Identify the names of the reactants and products
  and write a word equation.
• Write a formula equation by substituting correct
  formulas for the names of the reactants and
  products.
• Using coefficients, balance the formula equation
  according to the law of conservation of mass.
• Balance the different types of atoms one at a
  time.
• First balance atoms of elements that appear only
  once on each side.
• Balance polyatomic ions that appear on both sides
  as single units.
• Balance H and O atoms after atoms of other
  elements have been balanced.
• Count atoms to be sure the equation is balanced.

16
Balancing a Formula Equation

• hydrogen gas reacts with chlorine gas to produce
  hydrogen chloride gas
• _?_ H2(g) _?_ Cl2(g) ? _?_ HCl(g)
• H2(g) Cl2(g) ? 2 HCl(g)

17
Practice 1- Balance the following
formula equations.

• __CaF2 __Na2S ? __CaS __ NaF
• __FeS __ AlPO4 ? __Fe3(PO4)2 __Al2S3
• __Na __Cl2 ? __NaCl
• __H2 __O2 ? __H2O
• __C2H4 __O2 ? __CO2 __H2O
• __HBr __NaOH ? __NaBr __H2O
• __Na2SO4 __AlPO4 ? __Na3PO4 __Al2(SO4)3
• __N2 __O2 ? __N3O7
• __FePO4 __CaSO4 ? __Fe2(SO4)3 __Ca3(PO4)2
• __CuBr2 __NaF ? __CuF2 __NaBr

18
Balanced Formula Equation

• __CaF2 __Na2S ? __CaS __ NaF
• CaF2 Na2S ? CaS 2 NaF 1112
• __FeS __ AlPO4 ? __Fe3(PO4)2 __Al2S3
• 3 FeS 2 AlPO4 ? Fe3(PO4)2 Al2S3 3211
• __Na __Cl2 ? __NaCl
• 2 Na Cl2 ? 2 NaCl 212
• __H2 __O2 ? __H2O
• 2 H2 O2 ? 2 H2O 212
• __C2H4 __O2 ? __CO2 __H2O
• C2H4 3 O2 ? 2 CO2 2 H2O 1322

19
Practice

• __HBr __NaOH ? __NaBr __H2O
• HBr NaOH ? NaBr H2O 1111
• __Na2SO4 __AlPO4 ? __Na3PO4 __Al2(SO4)3
• 3 Na2SO4 2 AlPO4 ? 2 Na3PO4
  Al2(SO4)3 3221
• __N2 __O2 ? __N3O7
• 3 N2 7 O2 ? 2 N3O7 372
• __FePO4 __CaSO4 ? __Fe2(SO4)3 __Ca3(PO4)2
• 2 FePO4 3 CaSO4 ? Fe2(SO4)3
  Ca3(PO4)2 2311
• __CuBr2 __NaF ? __CuF2 __NaBr
• CuBr2 2 NaF ? CuF2 2 NaBr 1212

20
Practice Problems

• Do the following practice problems from the
  textbook
• practice 1 2 on page 272
• practice 1 (a, b, c) on page 274
• section review 2, 3, 4, 5 on
• page 274

21
Practice Problems page 272

• 1a) Mg HCl ? MgCl2 H2
• Mg 2 HCl ? MgCl2 H2
• 1b) HNO3 (aq) Mg(OH)2 (s) ? Mg(NO3)2 (aq) H2O
  (l)
• 2 HNO3 (aq) Mg(OH)2 (s) ? Mg(NO3)2 (aq) 2
  H2O (l)
• 2) Ca(s) H2O(l) ? Ca(OH)2 (aq) H2 (g)
• Ca(s) 2 H2O(l) ? Ca(OH)2 (aq) H2 (g)

22
Practice Problems page 274

• 1a) Na (s) Cl2 (g) ? NaCl (s)
• 2 Na (s) Cl2 (g) ? 2 NaCl (s)
• 1b) Cu (s) AgNO3 (aq) ? Cu(NO3)2 (aq) Ag (s)
• Cu (s) 2 AgNO3 (aq) ? Cu(NO3)2 (aq) 2 Ag
  (s)
• 1c) Fe2O3 (s) CO (g) ? Fe (s) CO2 (g)
• Fe2O3 (s) 3 CO (g) ? 2 Fe (s) 3 CO2 (g)

23
Section Review page 274

• 2) H2SO4 (aq) NaOH (aq) ? Na2SO4 (aq) H2O
  (l)
• H2SO4 (aq) 2 NaOH (aq) ? Na2SO4 (aq) 2 H2O
  (l)
• 3a) solid potassium plus liquid water produce
  aqueous potassium hydroxide and hydrogen gas
• 3b) solid iron metal plus chlorine gas yields
• solid iron (III) chloride
• 4) H2S (g) O2 (g) ? SO2 (g) H2O (g)
• 2 H2S (g) 3 O2 (g) ? 2 SO2 (g) 2 H2O (g)

24
Section Review page 274

• 5) VO Fe2O3 ? V2O5 FeO
• 2 VO 3 Fe2O3 ? V2O5 6 FeO

25
QUIZ 1- Balancing chemical equations

• Balance the following formula equations.
• 1- ___C3H8 ___O2 ? ___CO2 ___H2O
• 2- ___Al2(SO4)3 ___Fe3(PO4)2 ? ___AlPO4
  ___FeSO4
• 3- ___Na ___Cl2 ? ___NaCl
• 4- ___N2 ___O2 ? ___N3O7
• 5- ___NaNO3 ___Al2(CO3)3 ? ___Na2CO3
  ___Al(NO3)3

26
Types of Chemical Reactions

• synthesis reaction- also known as a composition
  reaction, two or more substances combine to form
  a new compound.
• A X ? AX
• Could be called the Boy Meets Girl reaction.

27
Types of Chemical Reactions

• decomposition reaction- a single compound
  undergoes a reaction that produces two or more
  simpler substances.
• AX ? A X
• The Boy Loses Girl reaction.

28
Types of Chemical Reactions

• single-displacement reaction- also known as a
  replacement reaction, one element replaces a
  similar element in a compound.
• A BX ? AX B
• The Boy Loses Girl to Best Friend reaction.

29
Types of Chemical Reactions

• double-displacement reaction- also known as a
  double replacement reaction, the ions of two
  compounds exchange places in an aqueous solution
  to form two new compounds.
• AX BY ? AY BX
• The Best Friends Trade Girlfriends Reaction.

30
Types of Chemical Reactions

• combustion reaction- a substance combines with
  oxygen, releasing a large amount of energy in the
  form of light and heat
• A O2 ? AO fire
• The Where Theres Smoke Theres Fire reaction.

31
Reaction Types Summary

• Synthesis A X ? AX
• Decomposition AX ? A X
• Single Displacement A BX ? AX B
• Double Replacement AX BY ? AY BX
• Combustion A O2 ? AO fire

32
QUIZ 2- Balance the following formula
equations then identify the reaction type.

• __Na __Br2 ? __NaBr
• reaction type
• __Fe2O3 ? __Fe __O2
• reaction type
• __CuI __F2 ? __CuF __I2
• reaction type
• __FeSO4 __Ca3(PO4)2 ? __Fe3(PO4)2 __CaSO4
• reaction type
• __C4H8 __O2 ? __CO2 __H2O (fire)
• reaction type

33
QUIZ 2- Balance the following formula
equations then identify the reaction type.

• __Na __Br2 ? __NaBr
• 2 Na Br2 ? 2 NaBr
• synthesis (composition)
• __Fe2O3 ? __Fe __O2
• 2 Fe2O3 ? 4 Fe 3 O2
• decomposition
• __CuI __F2 ? __CuF __I2
• 2 CuI F2 ? 2 CuF I2
• single replacement (single displacement)
• __FeSO4 __Ca3(PO4)2 ? __Fe3(PO4)2 __CaSO4
  
• 3 FeSO4 Ca3(PO4)2 ? Fe3(PO4)2 3 CaSO4
• double replacement (double displacement)
• __C4H8 __O2 ? __CO2 __H2O (fire)
• C4H8 6 O2 ? 4 CO2 4 H2O (fire)
• combustion

34
Types of Chemical Reactions

• synthesis reaction- also known as a composition
  reaction, two or more substances combine to form
  a new compound.
• A X ? AX

35
Journal Investigation- Synthesis Reaction

1. Get a strip of magnesium ribbon and an iron
   crucible from the front.
2. Roll the magnesium strip into a loose ball.
3. Weigh record the mass of the magnesium
   crucible on a scale.
4. Heat the crucible and magnesium using your burner
   until the magnesium begins to glow. Turn off the
   burner.
5. Allow the crucible to cool at least five minutes.
6. Weigh and record the new mass of the crucible
   magnesium oxide product.
7. Add three or four drops of tap water to the
   crucible. Waft the gas produced to attempt to
   smell the odor of ammonia.

36
Safety Precautions

• Burner equipment become very hot. DO NOT
  touch. Handle with crucible tongs.
• Eye protection MUST be worn due to possible
  sparks in the crucible.
• Safety apron is to be worn to protect skin
  clothing.
• Use a wafting technique when trying to detect
  ammonia smell.
• Rinse dry the cool crucible after lab is
  finished.

37
Journal Investigation- Synthesis ReactionANALYSIS

1. Using the recorded masses, show how this proves a
   synthesis reaction occurred.
2. The magnesium (Mg) combined with oxygen (O2) in
   the air to form a magnesium oxide (MgO) product.
   Write a balanced formula equation for this
   reaction.
3. When you added water, you should have smelled
   ammonia (NH3). The formula equation for this
   reaction would be Mg3N2 H2O ? Mg(OH)2 NH3.
   Balance this formula equation.
4. Where did the nitrogen come from to form the
   Mg2N3 as another product of this synthesis
   reaction?

38
Types of Chemical Reactions

• decomposition reaction- a single compound
  undergoes a reaction that produces two or more
  simpler substances.
• AX ? A X

39
Lab Investigation- Decomposition Reaction

1. Get a test tube with 5 10 mL of fresh hydrogen
   peroxide (H2O2) from the rack in the front of the
   room.
2. Add a match-head size amount of manganese dioxide
   (MnO2) to the test tube to act as a catalyst (a
   substance that speeds up a reaction without
   becoming part of it).
3. Observe the hydrogen peroxide for signs of a
   chemical reaction.
4. While the reaction is still taking place, set the
   end of a wooden splint on fire then blow it out.
5. While the splint is still glowing, lower it into
   the top of the test tube without touching the
   liquid. Observe the result. You can repeat this
   step several times until the reaction in the test
   tube stops.

40
Lab Investigation- Decomposition ReactionANALYSIS

1. Use your textbook to find the definition of a
   catalyst. Write the definition in the log.
2. What was the indication in the test tube that a
   chemical reaction was taking place?
3. Hydrogen peroxide decomposed into oxygen gas and
   liquid water. Write the balanced formula
   equation for this reaction.
4. What test was used to demonstrate that oxygen gas
   was a product of the reaction?
5. Write a balanced formula equation for the
   reaction between the carbon in the wood and the
   oxygen gas being produced. What type of chemical
   reaction is this?

41
Types of Chemical Reactions

• single-displacement reaction- also known as a
  replacement reaction, one element replaces a
  similar element in a compound.
• A BX ? AX B

42
Lab Investigation- Single Replacement Reaction

1. Get a small beaker with 20-25 mL. of silver
   nitrate (AgNO3). BE CAREFUL- silver nitrate will
   cause burn on your skin clothing.
2. Record in your journal the color of the silver
   nitrate solution.
3. Get a penny from your instructor.
4. Gently lower the penny into the beaker of silver
   nitrate making sure there is no splash.
5. Record observation of the penny in your journal
   for 10 minutes at 1 minute intervals.
6. Use a piece of tape to identify your beaker
   penny. Place the beaker in the fume hood
   overnight.
7. Record your observations after 24 hours. Be sure
   to include the color of the liquid in the beaker.

43
Lab Investigation- Single Replacement
ReactionANALYSIS

1. What were the indications that a chemical
   reaction had taken place?
2. What were the products of the single replacement
   reaction between copper (Cu) and silver nitrate
   (AgNO3)? (Assume the product contains the copper
   I ion.)
3. Write the balanced formula equation for the
   reaction between copper and silver nitrate.
4. Based on your observations, which element, copper
   or silver would appear higher on an activity
   series of metals? Why?

44
Types of Chemical Reactions

• double-displacement reaction- also known as a
  double replacement reaction, the ions of two
  compounds exchange places in an aqueous solution
  to form two new compounds.
• AX BY ? AY BX

45
Lab Investigation- Double Replacement Reaction

1. Get a test tube with 5 mL. of silver nitrate
   (AgNO3). BE CAREFUL- silver nitrate will cause
   burns on your skin clothing.
2. Record in your journal the color of the silver
   nitrate solution.
3. Get a test tube of sodium chloride (NaCl)
   solution. Record your observations of the
   solution.
4. Gently pour the sodium chloride into the test
   tube of silver nitrate making sure there is no
   splash.
5. Record your observation of the mixtures of the
   two aqueous solutions.
6. Take the test tubes to the front for disposal.

46
Lab Investigation- Double Replacement
ReactionANALYSIS

1. What were the indications that a chemical
   reaction had taken place?
2. What were the products of the double replacement
   reaction between sodium chloride (NaCl) and
   silver nitrate (AgNO3)?
3. Which of these products is the precipitate?
4. Write the balanced formula equation for the
   reaction between aqueous sodium chloride and
   aqueous silver nitrate.

47
Types of Chemical Reactions

• combustion reaction- a substance combines with
  oxygen, releasing a large amount of energy in the
  form of light and heat
• A O2 ? AO fire

48
Just for Fun- The Kandy Killer

• This will be a demonstration ONLY.
• We will be heating potassium chlorate (KClO3).
  This will cause it to undergo a decomposition
  reaction that produces potassium chloride and
  oxygen.
• A glowing splint will be used to confirm that
  oxygen is being produced.
• Candy will be dropped into the test tube. A
  rapid chemical reaction should be seen. YEA!!!

49
Practice Problems

• section review problems
• 1 through 5 on page 284 of the textbook.

50
Section Review page 284

• 1- List 5 types of reactions identified in this
  chapter.
• synthesis
• decomposition
• single displacement (replacement)
• double displacement (replacement)
• combustion
• 2a- N2 3H2 ? 2 NH3 synthesis
• b- 2Li 2H2O ? 2LiOH H2 single
  displacement
• c- 2NaNO3 ? 2NaNO2 O2 decomposition
• d- 2C6H14 19O2 ? 12CO2 14H2O combustion

51

• 3a-

52
QUIZ 3- Chemistry Chapter 8 Test Review

• Balance the following equations identify the
  reaction type.
• __Ca(NO3)2 __Na3PO4 ? __Ca3(PO4)2 __NaNO3
  reaction type
• __C4H8 __O2 ? __CO2 __H2O fire
  reaction type
• __H2 __Br2 ? __HBr reaction type
• __K __HBr ? __KBr __H2 reaction type
• __CaCO3 ? __CaO __CO2 reaction type

53
Activity Series of the Elements

• The activity of an element describes how it can
  react under specific conditions
• An activity series is a list of elements
  organized according to the ease with which
  elements undergo certain chemical reactions.

54
Activity Series of Metals

• Most reactive
• Li
• Rb React with cold water and acids,
• K replacing hydrogen.
• Ba React with oxygen forming oxides
• Sr
• Ca
• Na

55
Activity Series of Metals

• 2nd most reactive set
• Mg
• Al React with steam (but not cold
• Mn water) and acids, replacing
• Zn hydrogen. React with oxygen,
• Cr forming oxides.
• Fe
• Cd

56
Activity Series of Metals

• 3rd most reactive set
• Co Do not react with water.
• Ni React with acids, replacing hydrogen.
• Sn React with oxygen, forming oxides.
• Pb

57
Activity Series of Metals

• 4th most reactive set
• H2
• Sb React with oxygen, forming oxides.
• Bi
• Cu
• Hg

58
Activity Series of Metals

• Least reactive set
• Ag Fairly unreactive, forming oxides only
• Pt indirectly.
• Au

59
Activity of Halogen Non-metals

• The following halogens will replace any other
  halogen below it in a single replacement
  reaction.
• F2
• Cl2
• Br2
• I2

60
Practice Problems

• Use table 3 on page 286 of the textbook to answer
  Practice Problems 1 through 3 on page 287.

61
Practice problems page 287

• 1a- ____ Cr ____H2O (l) ? ?
• cannot occur- Cr will not react with water,
  only steam
• b- ____Pt ____O2 ? ?
• cannot occur-Pt does not form oxides directly
• c- ____Cd 2 HBr ? ? (HBr is an acid)
• can occur Cd reacts with acids to form hydrogen
• Cd 2 HBr ? CdBr2 H2
• d- ____Mg ____H2O(g) ? ? H2O (g) is
  steam
• can occur, Mg will react with steam to form
  hydrogen
• Mg(s) 2 H2O(g) ? Mg(OH)2 (aq) H2 (g)

62
Practice Problems page 287

• 2- Identify the element that replaces hydrogen
  from acids but does not replace tin from its
  compounds.
• Lead (Pb) replaces hydrogen from acids, but is
  below tin (Sn) in the activity series so it
  cannot replace tin (Sn).
• 3- According to table 3, what is the most active
  transition metal?
• As you go down the activity series of metals,
  manganese (Mn) is the first transition metal in
  the list, so it is the most reactive transition
  metal.

63
QUIZ 4- Chemistry Chapter 8 Test Review

• Use the activity series to determine if the
  following reactions are possible.
• 1) Sb HCl (an acid)?
• 2) K ZnCl2 ?
• 3) 2 HF Cl2 ?
• 4) 2 H2O (l) 2 Na ?
• 5) MgBr2 Cl2 ?

64
Chemistry Chapter 8 Test

• 25 multiple choice questions
• definition of a precipitate
• identify diatomic elements when used in chemical
  equations
• rules for balancing equations
• identify a word equation
• symbols used in equations (eg. aq)
• determine coefficients needed to balance
  equations
• identify reaction types by definition balanced
  formula equations
• definitions of activity activity series and how
  they are used

65
Honors Chemistry Chapter 8 Test

• 35 multiple choice questions
• chemical reactions law of conservation of mass
• indicators of chemical reactions
• definition of a precipitate and symbols used in
  equations
• identify a word equation a formula equation
• diatomic elements how they are written in an
  equation
• Identify coefficients needed to balance formula
  equations
• rules for balancing formula equations
• reaction types by definition balanced equations
• identifying predicting products of reactions
• definitions of activity activity series
• use activity series to predict products formed

66
Honors Chemistry Chapter 8 Test

• 1 short answer question
• When balancing a formula equation, why must the
  formula subscripts remain unchanged?
• 1 essay question
• Consider an equation. How does the equation
  violate the law of conservation of mass? How can
  the equation be rewritten to conform to the law
  of conservation of mass?
• 3 problems
• Write a balanced formula equation for a synthesis
  reaction when given the reactants product.
• Use an activity series to predict if a reaction
  can occur. If yes, write the balanced formula
  equation. (2 of these)