Chapter 8 Notes, Part IChapter 8 Notes, Part I
Parts of an equationParts of an equation
Types of reactionsTypes of reactions
What is a chemical reaction?What is a chemical reaction?
• A chemical reaction is the act of A chemical reaction is the act of changing substances into new changing substances into new substances with new and substances with new and different chemical and physical different chemical and physical properties.properties.
A Chemical EquationA Chemical Equation• A chemical equation shows what A chemical equation shows what
is going on in a chemical is going on in a chemical reaction.reaction.
• Instead of writing down the Instead of writing down the entire sentence “hydrogen entire sentence “hydrogen reacts with oxygen to form reacts with oxygen to form dihydrogen monoxide (water)”, dihydrogen monoxide (water)”, you could write…you could write…
2H2 + O22H2O
reactantsreactants
productsproducts
The substances you have before a chemical The substances you have before a chemical reaction occursreaction occurs
The substances you have after a chemical The substances you have after a chemical reaction occursreaction occurs
(found on the left side of the equation)(found on the left side of the equation)
(found on the right side of the equation)(found on the right side of the equation)
2H2 + O22H2O
subscriptssubscripts
coefficientscoefficients
How many elements are in a compoundHow many elements are in a compound
How many substances are in the How many substances are in the reactionreaction
2H2 + O22H2O
The arrow reads as “produces”, “yields” or “reacts to form”The arrow reads as “produces”, “yields” or “reacts to form”
4Fe + 3O22Fe2O3
Iron reacts with oxygen gas to produce iron Iron reacts with oxygen gas to produce iron (III) oxide(III) oxide
Other symbols in an Equation
•(s) = substance is solid•(l) = substance is liquid•(g) = substance is a gas•(aq) = substance is dissolved in water
• = heat
Other symbols in an Equation
•(A formula written above or below an arrow means it is a catalyst (a substance that speeds up a reaction without being used up by it.)
What is:
• The name of something that speeds a reaction, but is not used up?
• The name of what you have before a reaction takes place?
• The symbol for heat?• The number that shows there are
more than one of the entire compound?
Types of reactions
• There are five types of reactions–Combination–Decomposition–Single replacement–Double replacement–Combustion
Combination Reaction
•A combination reaction occurs when two or more elements or compounds combine to form a single substance.
•It will follow the form A + B AB
•Example: Fe + S FeS
Decomposition Reaction
•A decomposition reaction occurs when one substance breaks down into two or more substances.
•It will follow the pattern AB A + B
•Example: CaCO3CaO+CO2
Single Replacement Reaction
• One element replaces another element in a compound.
• Generally follows the formula:AB + C A + BC
• Example: Mg+Zn(NO3)2Zn+Mg(NO3)2
Double Replacement Reaction
• The exchange of two positive ions between two reacting compounds, forming two new compounds as a product.
• Generally follows the formula:AB + CD AD + CB
• Example:Na2S+Cd(NO3)2CdS+2NaNO3
Combustion Reaction
• A compound reacts with oxygen to producing energy as heat and light.
• Most of the time, it is a hydrocarbon reacting with oxygen, and the outcome is always carbon dioxide and water
• Follows the form: A + O2 CO2 + H2O
• Example: CH4 + O2 CO2 + 2H2O
What type of reaction is:
•NaCN + H2SO4 2HCN + Na2SO4
•Zn + 2HCl ZnCl2 + H2
•2C2H6 + 7O2 4CO2 + 6H2O
•2H2 + O2 2H2O
ON THE WHITEBOARDS:
•Tell which of the five types of reactions the following are:
2Na + 2H2O 2NaOH + H2
Single replacement
Fe + S FeScombination
Al(OH)3 + 3NaCl AlCl3 + 3NaOH
Double replacement
CH4 + 2O2 CO2 + 2H2Ocombustion
KClO2 KCl + O2
decomposition
NaOH + HCl NaCl + H2ODouble replacement
4Fe + 3O2 2Fe2O3
combination
2C2H2 + 5O2 4CO2 + 2H2Ocombustion
H2 + Cl2 2HClcombination
MgO + 2KF MgF2 + K2ODouble replacement
Na + Al(NO3)3NaNO3 + AlSingle replacement
2PbO2 2PbO + 3O2
decomposition
Ba(CN)2 + H2SO4 BaSO4 + HCNDouble replacement
C3H8 + 5O2 3CO2 + 4H2Ocombustion
4Li + O2 2Li2Ocombination
2Ag + 2HCl 2AgCl + H2
Single replacement
2H2O2 2H2O + O2
decomposition
C2H2 + O2 CO2 + H2Ocombustion
2HBr H2 + Br2
decomposition
CrSO4 + 2AgNO3 Cr(NO3)2 + Ag2SO4Double replacement