Chapter 11 Chemical Reactions

Hindenburg ShipHydrogen gas combined with Oxygen which caused the ship to catch fire

Chemical reactions

Take place after you eat

Photosynthesis

In a Chemical reactionOne or more substances change into one or more new substances

Writing chemical equations

Word Equations

Reactants

Products

Iron + Oxygen Iron(III) Oxide

Hydrogen Peroxide

Dihydrogen monoxide + OxygenMethane +

oxygen Carbon dioxide + Dihydrogen monoxide

Chemical Equations

Skeleton Equations- Equation that does not show the amounts of the reactants and the products

Fe + O2

Fe2O3

Unbalanced equation !!!!!

One can add more information to the skeleton equations:

To indicate if the reactants and products are liquids, solids or gases you use parentheses

Fe(s) + O2(g)

Fe2O3 (s)

To indicate a catalyst (a substance that speeds up the reaction but is not used in the reaction) you place the catalyst over the arrow

H2O2 (aq) H2O (l) + O2 (g)MnO2

Symbol Explanation+ Used to separate two reactants or

two products“yields”

Reaction is reversible(s) Solid state(l) Liquid state(g) Gaseous state(aq) Aqueous solution, dissolved in

waterHeat is applied to reactionCatalyst used in reaction

heat

catalyst

Balancing Equations

Reactants

Products

Frame + wheel + hanlebar + pedal

Bicycle

F + 2 W + 1 H + 2 P

FW2HP2

Calcium + Oxygen

Calcium Oxide

First write the skeleton equation

Ca + O2

CaO

Now balance

Ca + O2 CaO

1 Ca

1 Ca

2O 1 O

2

2

2

2

2Balanced

!!

Hydrogen + oxygenDihydrogen monoxideFirst write the skeleton equation

H2 + O2 H2O

Now balance

H2 + O2 H2O

2 H 2 H

2 O 1 O

Balanced

!!2

4

2

2

4

Types of Chemical Reactions5 Types

combination

decomposition

Single-replacement

Double-replacementcombustion

Combination Reactions

(Synthesis)Chemical change in which two or more substances react to form a single new substance

2 Mg(s) + O2(g)

2 MgO(s)

2 K(s) + Cl2(g) 2 KCl(s)

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

2 S (s) + 3 O2(g) SO3 (g)

Meta

l +

nonm

et

al

Two n

onm

eta

ls

two p

oss

ibili

ties

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

**Requires heat or electricity

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

2 H2O(l) electricity2 H2(g) + O2(g)

heat

Single-replacement ReactionsChemical change in which one element

replaces a second element in a compound

Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g)

Cl2(g) + 2 NaBr(aq) 2NaCl(aq) + Br2(aq)

Double-replacement ReactionsChemical change involving an

exchange of positive ions between two compounds

2 NaCN(aq) + H2SO4(aq) 2 HCN(aq) +

Na2SO4(aq)

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

Fe(OH)3(s) + 3 NaNO3(aq)

**Solution containing two ionic compounds

Combustion ReactionsChemical change in which an element or compound reacts with oxygen often producing energy in the form of heat or light

CH4 (g) + 2 O2(g)

CO2 (g) + 2 H2O(l)

2HCOOH (aq) + O2(g)

2CO2 (g) + 2 H2O(l)

hydrocarbon + oxygen carbon dioxide + water

** The number of elements and/or compounds reacting is a good indicator of possible reaction types and possible products- you can make predictions

Combination, decomposition, single-replacement, double-replacement, combustion

1.What are the five different types of reactions?

2.What type of reaction are the following?1. C3H6 + O2 → CO2 + H2O

2. Li + O2 → Li2O

3. Zn + AgNO3 → Ag + Zn(NO3)2

Check what you know!!

Combustion

Combination

Single-replacement

3.Predict the type of reaction that will occur?1.An aqueous solution of two ionic

compounds.

2.Reactant is a single compound.

3.The reactants are two elements.

4.The reactants are oxygen and a compound of carbon and hydrogen.

Double-replacement

Decomposition

Combination

Combustion

Reactions in Aqueous Solution

Net ionic equations are different that the equations we are used to writing. We used to write equations like this:

AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)

Net Ionic Equations

Many important reactions take place in

water

Complete Ionic EquationsShows the dissolved ionic compound as separate ionsAg+(aq) + NO3

-(aq) + Na+(aq) + Cl-

(aq) AgCl(s) + Na+(aq) + NO3- (aq)

Spectator ions - Ion that appears on both sides of the equation

but is not involved in the reaction

Net Ionic EquationsEquation that shows only the particles that are directly involved in the reaction

Ag+(aq) + Cl-

(aq)AgCl(s)

Predicting the formation of a precipitate

Compounds Solubility

Salts of alkali metals and ammonia

Soluble

Nitrate salts and chlorate salts

Soluble

Sulfate salts, except compounds with Pb, Ag, Hg, Ba, Sr, Ca

Soluble

Chloride salts except compounds with Ag, Pb, Hg

Soluble

Carbonates, phosphates, chromates, sulfides and hydroxides

Insoluble

Check what you know!!!

1.Write a balanced net ionic equation. Pb(NO3)2(aq) + H2SO4(aq) → PbSO4(s) +

HNO3(aq)

Then find the spectator ions and cross them out

Pb2+(aq) + NO3-

(aq) + H+(g) + SO4

2-(aq)

PbSO4(s)

+ H+(g) + NO3-

(aq)

First write the complete ionic equation

Finally, write the net ionic equationsPb2+

(aq) + SO4

2-(aq) PbSO4(s)