Transcript Chemical Reactions Section 9.1 Section 9.2 Section 9.3
Chemical Reactions
Reactions and Equations
Classifying Chemical Reactions
Reactions in Aqueous Solutions
Click a hyperlink or folder tab to view the corresponding slides.
Exit Chapter Menu
Section 9.1 Reactions and Equations
• • •
Recognize
evidence of chemical change.
Represent
chemical reactions with equations.
Balance
chemical equations.
chemical change:
a process involving one or
into a new substance
Chemical reactions are represented by balanced chemical equations.
chemical reaction reactant product chemical equation coefficient Section 9-1
Chemical Reactions
• The process by which one or more substances are rearranged to form different substances is called a
chemical reaction
.
• Evidence of a chemical reaction – Change in temperature (hot or cold) – Change in color (but not from dilution or mixing of colored solutions) – Odor, gas, or bubbles may form .
– Formation of a precipitate liquids) (solid from two Section 9-1
Representing Chemical Reactions
• Chemists use statements called equations to represent chemical reactions.
•
Reactants
are the starting substances.
•
Products
reaction.
are the substances formed in the • Reactants Products Section 9-1
• This table summarizes the symbols used in chemical equations.
Representing Chemical Reactions (cont.)
• In word equations ,
aluminum(s) + bromine(l) → aluminum bromide(s)
reads as: • “ aluminum and bromine react to produce aluminum bromide ”.
• Skeleton equations use symbols and formulas to represent the reactants and products.
Al(s) + Br(l) → AlBr 3 (s) • Skeleton equations lack many atoms information about are involved in the reaction.
how
Representing Chemical Reactions (cont.)
• A
chemical equation
is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.
Balancing Chemical Equations (cont.)
• The most fundamental law in chemistry is the law of conservation of mass .
• Balanced equations show this law.
• A
coefficient
in a chemical equation is the number written in front of a reactant or product, describing the lowest whole-number ratio of the amounts of all the reactants and products.
Describing Equations
Describing Coefficients
:
individual atom = “atom”
covalent substance = “molecule”
ionic substance = “unit” 3CO
2
2Mg
4MgO
3 molecules of carbon dioxide 2 atoms of magnesium 4 units of magnesium oxide
Balancing Chemical Equations
• This figure shows the balanced equation for the reaction between aluminum and bromine.
•
• • • • • •
Balancing Steps
Write the unbalanced equation.
Count atoms on reactant side.
Count atoms on product side.
Add coefficients to make #s equal.
Coefficient
subscript = # of atoms
Reduce coefficients to lowest whole # ratio, if necessary.
Double check your work!!!
Helpful Tips
• Balance one element at a time.
• Update ALL atom counts after adding a coefficient.
• If an element appears more than once per side, balance it last.
• Balance polyatomic ions as single units.
– “1 SO 4 ” instead of “1 S” and “4 O”
Balancing Example
Aluminum and copper(II) chloride react to form copper and aluminum chloride.
2
Al + CuCl
2
3
Cu + AlCl
3 2
1 1
2 3
3 6
6
Balancing Chemical Equations (cont.)
Section 9-1
• Balance the following:
Section 9.1 Assessment Which of the following is NOT a chemical reaction?
A.
a piece of wood burning
B.
a car rusting
C.
an ice cube melting into water
D.
red litmus paper turning blue
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Section 9-1
Section 9.1 Assessment What is the coefficient of bromine in the equation 2Al(s) + 3Br 2 (l) → 2AlBr 3 (s)? A.
1
B.
2
C.
3
D.
6
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Section 9-1
End of Section 9-1
Section 9.2 Classifying Chemical Reactions
•
Classify
chemical reactions.
•
Identify
the characteristics of different classes of chemical reactions.
metal:
an element that is a solid at room temperature, a good conductor of heat and electricity, and is generally shiny Section 9-2
Section 9.2 Classifying Chemical Reactions (cont.)
synthesis reaction combustion reaction decomposition reaction single-replacement reaction double-replacement reaction precipitate
There are five types of chemical reactions: synthesis, combustion, decomposition, single and double replacement reactions.
Section 9-2
Types of Chemical Reactions
• Chemists classify reactions in order to organize the many types.
• A
synthesis reaction
is a reaction in which two or more substances react to produce a single product .
Section 9-2
Types of Chemical Reactions (cont.)
• In a
combustion reaction
, oxygen combines with a substance and releases energy in the form of heat and light.
• Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.
Section 9-2
Types of Chemical Reactions (cont.)
• The burning of any substance in O 2 heat • Reactants Products to produce • Metal + Oxygen = Oxide • Nonmetal + Oxygen = of the metal Oxide of the nonmetal • Compound + Oxygen = Two or more oxides
A + O
2
AO
Decomposition Reactions
• A
decomposition reaction
is one in which a single compound breaks down into two or more elements or new compounds.
• Decomposition reactions often require an energy source , such as heat, light, or electricity, to occur.
AB
A + B
Section 9-2
Replacement Reactions
• A reaction in which the atoms of one element replace the atoms of another element in a compound is called a
single replacement reaction
.
• Metals replace metals (and Hydrogen) • Nonmetals replace 17 elements) nonmetals (usually group A + B X → A X + B Section 9-2
Replacement Reactions (cont.)
• A metal will not always replace a metal in a compound dissolved in water because of differing reactivities.
• An activity series can be used to predict if reactions will occur.
Section 9-2
Replacement Reactions (cont.)
•
Double replacement reactions
occur when ions exchange between two compounds.
Section 9-2
Replacement Reactions (cont.)
• The solid product produced during a chemical reaction in a solution is called a
precipitate
.
• All double replacement reactions produce either water, a precipitate, or a gas .
Section 9-2
Replacement Reactions (cont.)
Section 9-2
Replacement Reactions (cont.)
• Synthesis = A + B AB • Combustion = A + O 2 • Decomposition = AB AO A + B • Single-Replace = A + BX AX + B • Double-Replace = AX + BY AY + BX Section 9-2
Section 9.2 Assessment Which of the following is NOT one of the four types of reactions?
A.
deconstructive
B.
synthesis
C.
single replacement
D.
double replacement
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Section 9-2
Section 9.2 Assessment The following equation is what type of reaction?
KCN(aq) + HBr(aq) → KBr(aq) + HCN(g) A.
deconstructive
B.
synthesis
C.
single replacement
D.
double replacement
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Section 9-2
End of Section 9-2
Section 9.3 Reactions in Aqueous Solutions
•
Describe
aqueous solutions.
•
Write
complete ionic and net ionic equations for chemical reactions in aqueous solutions.
•
Predict
whether reactions in aqueous solutions will produce a precipitate, water, or a gas.
solution:
a uniform mixture that might contain solids, liquids, or gases Section 9-3
Section 9.3 Reactions in Aqueous Solutions (cont.)
aqueous solution solute solvent complete ionic equation spectator ion net ionic equation
Double-replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases.
Section 9-3
Aqueous Solutions
• An
aqueous solution
contains one or more dissolved substances (called
solutes
) in water.
• The
solvent
a solution.
is the most plentiful substance in Section 9-3
Aqueous Solutions (cont.)
• Water is always the solvent in an aqueous solution.
• There are many possible solutes—sugar and alcohol are molecular compounds that exist as molecules in aqueous solutions.
• Compounds that produce hydrogen ions in aqueous solutions are acids.
Section 9-3
Aqueous Solutions (cont.)
• Ionic compounds can also be solutes in aqueous solutions.
• When ionic compounds dissolve in water, their ions separate in a process called dissociation.
Section 9-3
Types of Reactions in Aqueous Solutions
• When two solutions that contain ions as solutes are combined, the ions might react.
• If they react, it is always a double replacement reaction.
• Three products can form: precipitates, water, or gases.
Section 9-3
Types of Reactions in Aqueous Solutions (cont.)
• Aqueous solutions of sodium hydroxide and copper(II) chloride react to form the precipitate copper(II) hydroxide.
2NaOH(aq) + CuCl 2 (aq) → 2NaCl(aq) + Cu(OH) 2 (s) • Ionic equations that show all of the particles in a solution as they actually exist are called
complete ionic equations
.
2Na + (aq) + 2OH – (aq) + Cu 2+ (aq)+ 2Cl – (aq) → 2Na + (aq) + 2Cl – (aq) + Cu(OH) 2 (s) Section 9-3
Types of Reactions in Aqueous Solutions (cont.)
• Ions that do not participate in a reaction are called
spectator ions
and are not usually written in ionic equations.
• Formulas that include only the particles that participate in reactions are called
net ionic equations
.
2OH – (aq) + Cu 2+ (aq) → Cu(OH) 2 (s) Section 9-3
Types of Reactions in Aqueous Solutions (cont.)
• Some reactions produce more water molecules.
• No evidence of a chemical reaction is observable.
HBr(aq) + NaOH(aq) → H 2 O(l) + NaBr(aq) • Without spectator ions H + (aq) + OH – (aq) → H 2 O(l).
Section 9-3
Types of Reactions in Aqueous Solutions (cont.)
• Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide.
2HI(aq) + Li 2 S(aq) → H 2 S(g) + 2LiI(aq) Section 9-3
Types of Reactions in Aqueous Solutions (cont.)
• Another example is mixing vinegar and baking soda, which produces carbon dioxide gas.
HCl(aq) + NaHCO 3 (aq) → H 2 CO 3 (aq) + NaCl(aq) • H 2 CO 3 (aq) decomposes immediately.
H 2 CO 3 (aq) → H 2 O(l) + CO 2 (g) Section 9-3
Types of Reactions in Aqueous Solutions (cont.)
• Two reactions can be combined and represented by a single chemical reaction.
Section 9-3
Types of Reactions in Aqueous Solutions (cont.) Reaction 1
HCl(aq) + NaHCO 3 (aq) → H 2 CO 3 (aq) + NaCl(aq)
Reaction 2
H 2 CO 3 (aq) → H 2 O(l) + CO 2 (g)
Combined equation
HCl(aq) + NaHCO 3 (aq) + H 2 CO 3 (aq) → H 2 CO 3 (aq) + NaCl(aq) + H 2 O(l) + CO 2 (g)
Overall equation
HCl(aq) + NaHCO 3 (aq) → H 2 O(l) + CO 2 (g) + NaCl(aq) Section 9-3
Section 9.3 Assessment What is the solvent in an aqueous solution? A.
hydrogen
B.
sodium ions
C.
water
D.
alcohol
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Section 9-3
Section 9.3 Assessment An equation that includes only the particles that participate in a reaction is called: A.
net ionic equation
B.
spectator ions
C.
complete ionic equation
D.
reduced ionic equation
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Section 9-3
End of Section 9-3
Chemistry Online Study Guide Chapter Assessment Standardized Test Practice Image Bank Concepts in Motion Resources Menu
Section 9.1 Reactions and Equations Key Concepts
• Some physical changes are evidence that indicate a chemical reaction has occurred. • Word equations and skeleton equations provide important information about a chemical reaction.
• A chemical equation gives the identities and relative amounts of the reactants and products that are involved in a chemical reaction. • Balancing an equation involves adjusting the coefficients until the number of atoms of each element is equal on both sides of the equation.
Study Guide 1
Section 9.2 Classifying Chemical Reactions Key Concepts
• Classifying chemical reactions makes them easier to understand, remember, and recognize.
• Activity series of metals and halogens can be used to predict if single-replacement reactions will occur.
Study Guide 2
Section 9.3 Reactions in Aqueous Solutions Key Concepts
• In aqueous solutions, the solvent is always water. There are many possible solutes.
• Many molecular compounds form ions when they dissolve in water. When some ionic compounds dissolve in water, their ions separate. • When two aqueous solutions that contain ions as solutes are combined, the ions might react with one another. The solvent molecules do not usually react.
• Reactions that occur in aqueous solutions are double replacement reactions.
Study Guide 3
The law of conservation of mass requires what in a chemical reaction equation?
A.
both sides of the equation to contain the same substances
B.
C.
the reactants to have the same amount of molecules as the products both sides to have the same amount of atoms of each element
D.
the products to have fewer molecules than the reactants
0% A
A. A B. B C. C
B 0% 0%
D. D
C 0% D
Chapter Assessment 1
A reaction that gives off heat is what type of reaction?
A.
single replacement reaction
B.
double replacement reaction
C.
synthesis reaction
D.
combustion reaction
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Chapter Assessment 2
Ions that are present in a solution and do not participate in a chemical reaction when another substance is added are called ____. A.
spectator ions
B.
reactants
C.
products
D.
net ions
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Chapter Assessment 3
A double replacement reaction produces all of the following except ____. A.
gases
B.
solids
C.
light
D.
water
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Chapter Assessment 4
What type of reaction is the following?
2H 2 O(l) + energy → H 2 (g) + O 2 (g) A.
synthesis reaction
B.
decomposition reaction
C.
combustion reaction
D.
replacement reaction
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
Chapter Assessment 5
What type of reaction is the following?
2H 2 (g) + O 2 (g) → 2H 2 O(l) A.
replacement reaction
B.
synthesis
C.
combustion reaction
D.
double replacement reaction
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
STP 1
A precipitate forms in a double replacement reaction only if: A.
the reactivities of the compounds differ
B.
the new compound is denser than water
C.
the new compound is soluble in water
D.
the new compound is not soluble in water
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
STP 2
A ____ is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.
A.
word equation
B.
skeleton equation
C.
chemical equation
D.
balanced equation
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
STP 3
Predict the type of reaction.
LiBr 2 (aq) + 2NaOH (aq) → ____ A.
synthesis reaction
B.
combustion reaction
C.
single replacement reaction
D.
double replacement reaction
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
STP 4
Which reactions are essentially the opposite of synthesis reactions?
A.
single-replacement
B.
decomposition
C.
combustion
D.
double-replacement
A 0%
A. A B. B
B 0%
C. C
0%
D. D
C 0% D
STP 5
Click on an image to enlarge.
IB Menu
IB 1
IB 2
IB 3
IB 4
IB 5
IB 6
IB 7
IB 8
IB 9
IB 10
IB 11
IB 12
Table 9.2 Steps for Balancing Equations Figure 9.15 The Forming of a Precipitate Table 9.4 Types of Chemical Reactions CIM
Click any of the background top tabs to display the respective folder.
Within the Chapter Outline, clicking a section tab on the right side of the screen will bring you to the first slide in each respective section.
Simple navigation buttons will allow you to progress to the next slide or the previous slide.
The Chapter Resources Menu will allow you to access chapter specific resources from the Chapter Menu or any Chapter Outline slide. From within any feature, click the Resources tab to return to this slide.
The “Return” button will allow you to return to the slide that you were viewing when you clicked either the Resources or Help tab.
To exit the presentation, click the Exit button on the Chapter Menu slide or hit Escape [Esc] on your keyboards while viewing any Chapter Outline slide.
Help
This slide is intentionally blank.
End of Custom Shows