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)