chemical equations & reactions chapter 8. objectives list observations that suggest that a...
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Chemical Equations & Reactions
Chapter 8
Objectives List observations that suggest that a
chemical reaction has taken place. List three requirements for a correctly
written chemical equation. Write a word equation and a formula
equation for a given chemical reaction. Balance a formula equation by inspection.
Chemical Reaction
Process by which one or more substances are changed into one or more different substances
Indications of a Chemical Reaction
1. Evolution of heat & light
Indications of a Chemical Reaction
2. Production of a gas
Indications of a Chemical Reaction
3. Formation of a precipitate
Precipitate
A solid that is produced as a result of a chemical reaction in solution & that separates from the solution
Indications of a chemical reaction
4. Change in color. (sumac leaves change color when chlorophyll is destroyed)
Chemical Equation
Representation, with symbols and formulas, of the identities and relative amounts of the reactants and products in a chemical reaction
Reactants Products
Follows the Law of Conservation of Mass
Characteristics of Chemical Equations
The equation must represent known facts
The equation must contain the correct formulas for the reactants & products
The law of conservation of mass must be satisfied- which means the same # and type of atoms are present on both sides of the equation.
Word Equation
Represents facts- only qualitative
Example:Methane + oxygen carbon dioxide + water
Writing Chemical EquationsWriting Chemical Equations
Example:
CH4(g) + O2(g) CO2(g) + H2O(g)
(not balanced)
Symbols you will see in equations pg.266
Formula Equation
Writing Chemical EquationsWriting Chemical Equations
Inserting Coefficients-small whole # that appears in front of a formula
Multiplies number of atoms of each element indicated in chemical formula
Example:
CH4(g) + 2O2(g) CO2(g) + 2H2O(g)
Balanced Formula Equation
Writing Chemical EquationsWriting Chemical Equations
Balancing Chemical Equations
Balance the formula equation according to the law of conservation of mass Balance the different types of atoms one at a
time Balance polyatomic ions that appear on both
sides of the equation as single units Balance H atoms and O atoms after atoms of
all other elements have been balanced
Examples
Mg + HCl MgCl2 + H2
Al2(SO4)3 + Ca(OH)2 Al(OH)3 + CaSO4
MgI2 + KNO3 KI + Mg(NO3)2
Writing and Balancing Equations from Word Equations
1. Write out correct chemical formulas and symbols.
2. Balance equation.
Solid aluminum metal combines with oxygen gas to produce solid aluminum oxide
Writing equations from word equations
Examples to try.1. Solid calcium metal reacts with water to form
aqueous calcium hydroxide and hydrogen gas.
2. Solid iron(III)oxide and carbon monoxide gas produces solid iron and carbon dioxide gas.
3. Solid copper reacts with aqueous silver nitrate to produce aqueous copper (II) nitrate and solid silver.
Objectives Define & give general equations for
synthesis, decomposition, single-replacement, and double-replacement reactions.
Classify a reaction as synthesis, decomposition, single displacement, double displacement or combustion.
Predict the products of simple reactions if given the reactants.
5 Basic Types of Reactions Synthesis Decomposition Single-replacement Double-replacement Combustion
Synthesis Reactions A reaction in which two or more
substances combine to form a new compound
A + X AX
A and X are elements or compounds
AX is a compound
Synthesis Reactions Examples:
magnesium + oxygen __________
iron + oxygen __________
calcium oxide + water __________
Decomposition Reactions A reaction in which a single compound
produces two or more simpler substances Opposite of synthesis reactions
AX A + X
AX is a compound
A and X are elements or compounds
Decomposition Reactions(Binary Compounds)
Decomposition of a binary compound into its elements.
Example:
water __________ + __________
Electrolysis
The decomposition of a substance by an electric current
Decomposition Reactions(Metal Carbonates)
Metal carbonates decompose to produce a metal oxide & carbon dioxide gas.
Example:
calcium carbonate ______ + ______
Decomposition Reactions(Metal Hydroxides)
Metal hydroxides (except group 1 metals) decompose to produce metal oxides & water.
Example:
calcium hydroxide ______ + ______
Single-Replacement Reactions A reaction in which one element replaces
a similar element in a compound
A + BX AX + B
- or –
Y + BX BY + X A, B, X, Y are elements AX, BX, BY are compounds
Single-Replacement Reactions(Replacement of a Metal or Nonmetal)
Example:
aluminum + lead nitrate ____ + ____
fluorine + sodium chloride ____ + ____
Double-Replacement Reactions
A reaction in which the ions of two compounds exchange places in an aqueous solution to form two new compounds
AX + BY AY + BX A, X, B, Y in reactants represent ions AY & BX represent ionic or molecular
compounds
Double-Replacement Reactions(Formation of a Precipitate)
One cation of one reactant combine with the anions of another reactant to form insoluble or slightly soluble compound
Example:
Potassium iodide + lead (II) nitrate ____
+ ____
Double-Replacement Reactions(Formation of a Gas)
Example:
Iron(II) sulfide + hydrochloric acid ____
+ ____
Double-Replacement Reactions(Formation of Water)
Example:
hydrochloric acid + sodium hydroxide ____
+ ____
Combustion Reactions
A reaction in which a substance combines with oxygen, releasing a large amount of energy in the form of light and heat
Combustion of a hydrocarbon always yield carbon dioxide and water.
Combustion Reactions
Example:
propane + oxygen ____ + ____
(C(C33HH88))
Try this: Write a balanced chemical equation for the
following reaction:
Ethyl alcohol (C2H5OH) burns to produce carbon dioxide and water.
Objectives Explain the significance of an activity
series. Use an activity series to predict whether a
given reaction will occur and what the products will be.
Activity Series A list of elements organized according to
the ease with which the elements undergo certain chemical reactions
Used to help predict whether certain chemical reactions will occur
Activity Series Table 8.3, p. 286 An element can replace any element
below it but not above it Based on experiment Will be given to you on test.
Examples Using the activity series, predict whether
each of the possible reactions will occur. For the reactions that will occur, write the products & balance the equation.
Ba(s) + H2O(l)
Cu(s) + HBr(aq) Al(s) + HBr(aq) F2(g) + NaCl(s)