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: 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 (NH4)2Cr2O7(s) ---> N2(g) + Cr2O3(s) + 4H2O(g) 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 + H2O Cu 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: synthesis (composition) decomposition single-replacement (displacement) double-replacement (displacement) 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 acid oxygen

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 