Chemical Reactions

Classifying Reactions

The five general types of reaction are combination, decomposition, single-replacement,

double-replacement, and combustion.

Synthesis/Combination

A combination reaction is a chemical change in which two or more substances react to form a single new substance.

Synthesis/Combination

Products: It will always just produce ONE product Group A metal and a nonmetal react, the compound is the

metal cation and the nonmetal anion2K(s) +Cl2(g) 2KCl(s)

When two nonmetals react in a combination reaction, more than one product possible

S(s) + O2(g) SO2(g)

2S(s) + 3O2(g) 2SO3(g) More than one product may also result from the

combination reaction of a transition metal and a nonmetalFe(s) + S(s) FeS(s)

2Fe(s) + 3S(s) Fe2S3(s)

Practice with Synthesis Reactions

Complete and balance this equation for a combination reaction.

Be + O2

Write and balance the equation for the formation of magnesium nitride (Mg3N2) from its elements.

DecompositionA decomposition reaction is a chemical

change in which a single compound breaks down into two or more simpler products.

DecompositionProducts: The products can be any combination

of elements and compounds. Usually difficult to predict. A simple binary compound will break

down to its constituents. Most decomposition reactions require

energy in the form of light, heat or electricity

2HgO(s) 2Hg(l) + O2(g)

Practice with Decomposition

Complete and balance this decomposition reaction

HI

Write the formula for the binary compound that decomposes to the products H2 and Br2

Single Replacement

A single replacement reaction is a chemical change in which one element replaces a

second element in a compound.

Single Replacement Reaction

Whether one metal will displace another metal from a compound depends upon the relative reactivities of the

two metals.

A reactive metal will replace any metal listed below it in the activity series.

Single Replacement

A halogen can replace another halogen from a compound. The activity of the halogens

decrease as you go down.

Br2(aq) + NaI(aq) NaBr(aq) + I2(aq)

Br2(aq) + NaCl(aq) No Reaction

Practice with Single Replacement ReactionsComplete the equations for these single

replacement reactions in aqueous solution. Balance each equation. Put “no reaction” if a

reaction does not occur.

Fe(s) + Pb(NO3)2(aq)

Cl2(aq) + NaI(aq)

Ca(aq) + H2O(l)

Double Replacement Reaction

A chemical change involving an exchange of positive ions between two compounds.

Practice with Double Replacement

Write the products of these double-replacement reactions. Then balance each

equation.NaOH(aq) + Fe(NO3)3(aq)

(Iron(III)hydroxide is a precipitate)

Ba(NO3)2(aq) + H3PO4(aq)

(Barium phosphate is a precipitate)

Combustion Reactions

A combustion reaction is a chemical change in which an element or a compound reacts with

oxygen, often producing energy in the form of heat and light.

2C8H18(l) + 25O2(g) 16CO2(g) + 18H2O(l)

The complete combustion of a hydrocarbon produces carbon dioxide and water.

Practice with Combustion Reactions

Write a balanced equation for the complete combustion of each compound.

Formic acid (HCOOH)

Heptane (C7H16)