REACTANTS PRODUCTS 1.  Starting substances (reactants) becomes new substances (products).

2. Bonds are broken and new bonds are formed, but atoms are not created or destroyed (just rearranged).

Law of Conservation of Mass

PRODUCTSREACTANTS

SENTENCE EQUATIONIron reacts with oxygen to produce rust

WORD EQUATION Iron + oxygen iron (III) oxide

SKELETON EQUATIONFe + O2 Fe2O3

These DO NOT indicate the relative amounts of the reactants and products.

BALANCED EQUATION◦most correct equation ◦includes the physical states of each

substance◦uses coefficients

4Fe(s) + 3O2(g)2 Fe2O3(s)◦Learn chart of symbols on page 206 in

text.

A) Skeleton equationB) Word equationC) Sentence equationD) Balanced equation

A) Skeleton equationB) Word equationC) Sentence equationD) Balanced equation

Reactions are classified into five basic types. To be sure there are more than five types and many are combinations of these types.◦ Combination (synthesis) (c)◦ Decomposition (d)◦ Single-Replacement (single displacement-sr)◦ Double Replacement (double displacement-dr)◦ Combustion (comb)

See page 222 -great summary of these types.

Two or more substances combine to form a single substance

Basic equation◦ A + B → AB◦If metal and non-metal, product is ionic◦If two non-metals, product is molecular

A single compound is broken down into two or more products

Basic equation AB →A + B

Produces a combination of elements and compounds. Products hard to predict.

Most require heat or light, or electricity

Atoms of one element replace the atoms of another element (single displacement)

Basic equation A + BC → AC + B if A is a metal A + BC → BA + C if A a non-metal

Involves the changing of positive ions between two compounds

Usually results in:◦Formation of precipitate◦Formation of a gas◦Formation of water

Basic equation AB + CD →AD + CB

A compound reacts with OXYGEN (O2) to

produce energy in the form of heat and/or light.

When a compound containing carbon and hydrogen (called a hydrocarbon) burns in air the products are carbon dioxide and water. Called complete combustion

◦CH4 + 2O2 → CO2 + 2H2O

Complete combustion assumes an ample supply of oxygen.

Incomplete combustion occurs with limited oxygen supply.Products of incomplete combustion are carbon monoxide and water.◦2CH4 + 3O2 → 2CO+ 4H2O

Can also combust other non-metals or metals◦Recall burning magnesium

A catalyst is used to speed up the rate of a chemical reaction but is NOT used up in the reaction.In bio, a catalyst is called an enzyme.

A) SynthesisB) DecompositionC) Single replacementD) Double replacementE) Combustion

A) SynthesisB) DecompositionC) Single replacementD) Double replacementE) Combustion

Many reactions take place in aqueous systems (especially biological ones)

Can write various kinds of equations to describe these reactions◦Single replacement reactions ◦Double replacement reactions

A precipitate may form when two aqueous solutions are mixed.

Precipitate - a substance that falls out of solution when it is one of the products of a reaction.

◦ Precipitates are insoluble in water.◦ The symbol for a precipitate is in a

word equation◦ The symbol in a chemical equation (s)

for solid

No visible reaction (nvr)◦ No insoluble substance formed

Formation of one ppt.◦ Insoluble substance formed

Formation of two ppt. (rarely occurs)◦ Two separate insoluble substances formed

Complete molecular equationAgNO3 (aq) + KBr (aq) → KNO3 (?) +AgBr (?) Does a ppt form?Use a solubility chart….

Complete molecular equationAgNO3 (aq) + KBr (aq) → KNO3 (?) +AgBr (?) Does a ppt form?Use a solubility chart…..

AgNO3 (aq) + KBr (aq) → KNO3 (aq) +AgBr (s)

AgNO3(aq) + KBr(aq) → KNO3(aq) +AgBr(s)

a. Why don’t Ag and K ions go together?

b. Why don’t the bromide and nitrate ions go together?

c. What determines if resultant formula written as AgBr or BrAg?

OUTERS

INNERS