Chemical Reactions and Equations Chapter 8
Jan 05, 2016
Chemical Reactions and Equations
Chapter 8
Chemical reactions….• Process by which one or more substances are
• described by a
4 Signs of a Chemical Reaction:1. Evolution of _________ and
________________2. Production of ______________3. Formation of a
_____________________(solid produced as a result of a chem rxn in a sol’n)
4. _____________________change
Chemical equation• Represents the identities and relative amounts of the
reactants and products in a chemical reaction
• (NH4)2Cr2O7(s) ---> N2(g) + Cr2O3(s) + 4H2O(g)
Characteristics:– represents the _______________________________
– contains correct _________________ for the reactants & products
– satisfies the law of ____________________________ (same # and kind of atoms on both sides of the equation)
(NH4)2Cr2O7(s)---> N2(g) + Cr2O3(s) + 4H2O(g)
• Formula equation: uses symbols/formulas to represent the reactants and products
• Reactants
• products
• coefficient (understood to be “1” if no # appears
• symbols (p.246)
ammonium dichromate --> nitrogen + chromium(III) oxide + water
• Word equation: (previous ex.)
• only fulfills ONE characteristic of a chem eq
(____________________________________)
• 1st step in writing a balanced chemical equation
Steps to write a balanced chemical equation:
1. Write the word equation.
2. Convert the word equation into a formula equation.
3. Include symbols, where known.
4. Balance the equation. NEVER CHANGE A SUBCRIPT IN BALANCING EQUATIONS!
Cu + H2SO4 CuSO4 + SO2 + H2OCu
H
S
O
Cu + H2SO4 CuSO4 + SO2 + H2O
SiF4 + H2O H2SiF6 + H2SiO3
Si
F
H
O
SiF4 + H2O H2SiF6 + H2SiO3
Solutions of lead(II) nitrate and sodium hydroxide react to produce a lead(II) hydroxide precipitate and an aqueous solution of sodium nitrate.
Solid rubidium oxide reacts with water to produce an aqueous solution of rubidium
hydroxide.
Lithium reacts with a hydrochloric acid solution to produce an aqueous solution of
lithium chloride and hydrogen.
In the presence of an electrical current, sodium hydroxide can be produced from the reaction of a sodium chloride solution with water. Hydrogen and chlorine gases are the other products.
Aluminum sulfate is produced when aluminum hydroxide reacts with sulfuric acid. Water is the other product.
5 types of chemical reactions:
1. synthesis (composition)
2. decomposition
3. single-replacement (displacement)
4. double-replacement (displacement)
5. combustion
Synthesis Reactions
• 2 or more substances combine to form a new compound
• 2 H2 + O2 2H2O
Reactions of metals with oxygen and sulfur
• magnesium metal + oxygen
• barium + sulfur (S8)
Some metals can form oxides of varying oxidation #:
• iron + oxygen iron(II) oxide
• iron + oxygen iron(III) oxide
Nonmetals can also form oxides
• S8(s) + 8O2(g) 8SO2(g)
• C(s) + O2(g) CO2(g)
• 2C(s) + O2(g) 2CO(g)
Reactions of metals with halogens• potassium + iodine
• strontium + bromine
• cobalt + fluorine [cobalt(III) ion forms]
Synthesis reactions with metal oxides
• active metals* oxides + water hydroxides
• calcium oxide + water
• *(see p. 266)
Synthesis reactions with nonmetal oxides
• nonmetal oxides + water oxyacids
• sulfur dioxide + water
Synthesis reaction of metal oxide & nonmetal oxide
• calcium oxide + sulfur dioxide
Decomposition
• a single cmpd undergoes a rxn that produces 2 or more simpler substances
•H2CO3 H2O + CO2
Decomposition of…
• binary cmpds
• metal carbonates
• metal hydroxide
• metal chlorates
• acid
Decomposition of binary cmpds
• simplest decomposition rxn
• decomposition into elements
• ELECTROLYSIS: decomp by an electric current
• 2 H2O(l) electricity--->
Decomposition of Metal Carbonates
• when heated (∆), produce a metal oxide and carbon dioxide gas
• CaCO3(s) -∆
Decomposition of Metal Hydroxides
• all metals except Gp 1 decomp when heated to produce metal oxides and water
• Ca(OH)2(s) -∆ CaO(s) + H2O(g)
Decomposition of Metal Chlorates
• when heated, decompose to produce a metal chloride and oxygen
• KClO3(s) -∆ 2KCl(s) + 3O2(g)
Decomposition of Acids
• Many acids decompose into nonmetal oxides and water
• H2SO4(aq) -∆
• H2CO3(aq)
Single Replacement Reaction
• one element replaces a similar element in a cmpd
• 2 Al + Fe2O3 Al2O3 + 2 Fe
Single Replacement Reaction of…
• a metal in a cmpd by another metal
• hydrogen in water by a metal
• hydrogen in an acid by a metal
• replacement of halogens
Replacement of a metal in a cmpd by another metal
• aluminum + lead(II) nitrate
• (p. 266 Al is more reactive than Pb so a spontaneous reaction will occur)
Replacement of H in water by a metal (active)
very active metals (i.e. Gp 1) pulls one H from the water
• sodium + water
Replacement of H in water by a metal (less-active)
less- active metals reacts with steam and pulls-off both hydrogens from the water
• iron + water
Replacement of H in an acid by a metal
more-active metals reacts with some acidic soln’s
• magnesium + hydrochloric acid
Replacement of Halogens• a more reactive halogen will replace a
less-active halogen
• the higher up in the Gp 17 family, the MORE reactive the halogen
• Reactivity: F>Cl>Br>I
• chlorine gas + potassium bromide sol’n
• fluorine gas + sodium chloride sol’n
• bromine liquid + potassium chloride sol’n
Double replacement reactions
• ions of 2 cmpds exchange places in an aqueous solution to form 2 new cmpds
• ZnBr2 + 2 AgNO3 Zn(NO3)2 + 2 AgBr
Double displacement reactions…..
• formation of a precipitate
• formation of a gas
• formation of water
Formation of a precipitate
• one product is insoluble (or just slightly soluble) …see page 427
• potassium iodide + lead (II) nitrate
Formation of a gas• one product is an insoluble gas and bubbles
out
• iron(II) sulfide + hydrochloric acid sol’n
Formation of Water
• one of the products yields the molecular cmpd water
• hydrochloric acid + sodium hydroxide
Combustion Reactions
• substance reacts with oxygen and releases a large amount of energy (light and heat)
• hydrogen + oxygen water vapor
• hydrocarbon + oxygen carbon dioxide + water
• Combustion (burning) of propane:
• C3H8(g) + O2
Will cobalt react with sodium chloride?
Co(s) + NaCl(aq) ?
Activity Series
• list of elements organized according to the ease with which the elements undergo certain chemical reactions
• are
at the TOP and can replace a metal in a cmpd found below it in single displacement reactions
water
X
steam
X
acid
X
oxygen
X
X X X
X X
X
Will the following react? IF so, write an equation.
• Mn + H2O --30C ?
• Cd + O2
• Ag + HCl
Will the following react? Write an equation if it does.
• Br2 and HCl
• Cl2 and KI