Reactants Products Fe + O2 Fe2O3

A catalyst is a substance that speeds up the reaction but is not changed by it.

It is neither a reactant or a product.

Release of a gas◦ CO2 is released when acid is placed in a solution

containing CO32- ions

Formation of a solid (precipitate)◦ A solution containing Ag+ ions mixed with a

solution containing Cl- ions Heat is produced or absorbed

◦ Acid and base are mixed together Color changes

Symbol Meaning forms, produces↔ reversible reaction(s) Solid state(l) Liquid state; water only(g) Gaseous state(aq) aqueous state, all liquids besides

water

heat/energy is supplied to the reaction

Catalyst is used, here platinum

PT

)(O )2Hg( )2HgO( 2 gls

ProductsProducts – written on the right

Reactants – written on the left of arrow

Products and reactants must be specified using chemical symbols

Physical states are shown in parentheses

– energy is needed

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

Identify the substance involved Coefficients - how many? Chemical Formula – of what? Physical State – in what state? Remember Diatomic Elements

◦ Magic Seven

Two atoms of aluminum react with three units of aqueous copper (II) chloride to produce three atoms of copper and two units of aqueous aluminum chloride?◦ How many?◦ Of what?◦ What physical state?

Two atoms of aluminum react with three units of aqueous copper (II) chloride to produce three atoms of copper and two units of aqueous aluminum chloride?◦ How many?◦ Of what?◦ What physical state?

2 Al(s) + 3 CuCl2(aq) 3 Cu(s) + 2AlCl3(aq)

Describing Coefficients:

◦individual atom = “atom”

◦covalent substance = “molecule”

◦ionic substance = “unit”

3CO3CO22

2Mg 2Mg

4MgO 4MgO

Describing Coefficients:

◦individual atom = “atom”

◦covalent substance = “molecule”

◦ionic substance = “unit”

3 molecules of carbon 3 molecules of carbon

dioxidedioxide

2 atoms of magnesium2 atoms of magnesium

4 units of magnesium oxide4 units of magnesium oxide

3CO3CO22

2Mg 2Mg

4MgO 4MgO

• How many?• Of what?• In what state?

Zn(Zn(ss) + 2HCl() + 2HCl(aqaq) ) ZnCl ZnCl22((aqaq) + H) + H22((gg))

One atom of solid zinc reacts with two units of aqueous hydrochloric acid to produce one unit of aqueous zinc chloride and one molecule of hydrogen gas

• How many?• Of what?• In what state?

Zn(Zn(ss) + 2HCl() + 2HCl(aqaq) ) ZnCl ZnCl22((aqaq) + H) + H22((gg))

Law of conservation of mass - matter cannot be created or destroyed

◦ mass of the products = mass of the reactants Coefficient: # of moles of products &

reactants

◦4Fe + 3O2 2Fe2O3

Diatomic elements (The Magic 7)H2, N2, O2, F2, Cl2, Br2, I2

)(O )2Hg( )2HgO( 2 gls

Coefficient - how many of that substance are in the reaction

The equation must be balanced ◦ All the atoms of every reactant must also appear

in the products Number of Hg on left? 2

◦ on right 2 Number of O on left? 2

◦ on right 2

H2 + O2 H2O

Is the law of conservation of mass obeyed as written? ◦ NO

You never change subscripts

◦ WRONG: H2 + O2 H2O2

Step 1. Count the number of moles of atoms of each element on both product and reactant sides

Reactants Products 2 mol H 2 mol H 2 mol O 1 mol O

The steps to balancing:

H2 + O2 H2O

Step 2. Determine which elements are not balanced – Oxygen is not balanced

Step 3. Balance one element at a time by changing the coefficients

H2 + O2 2H2O This balances oxygen, but is hydrogen still

balanced?

2H2 + O2 2H2O

Step 4. Make sure the law of conservation of mass is obeyed

Reactants Products 4 mol H 4 mol H 2 mol O 2 mol O

Balance the following equations:

1. C2H2 + O2 CO2 + H2O

2. AgNO3 + FeCl3 Fe(NO3)3 + AgCl

3. C2H6 + O2 CO2 + H2O

4. N2 + H2 NH3

Balance the following equations:

1. 2C2H2 + 5O2 4CO2 + 2H2O

2. 3AgNO3 + FeCl3 Fe(NO3)3 + 3AgCl

3. 2C2H6 + 5O2 4CO2 + 6H2O

4. N2 + 3H2 2NH3

A + B AB

Synthesis reactions

The joining of two or more elements or compounds, producing a product of different composition

Examples: metal + nonmetal salt: 2Na(s) + Cl2(g)

2NaCl(s) H + Cl HCl MgO(s) + CO2(g) MgCO3(s)

AB A + B

Produce two or more products from a single reactant

Reverse of a combination reaction

Examples: 2HgO(s) 2Hg(l) + O2(g) CaCO3(s) CaO(s) + CO2(g) Removal of water from a hydrated material

Single-replacement

• One atom replaces another in the compound producing a new compound

Examples:• Cu(s)+2AgNO3(aq) 2Ag(s)+Cu(NO3)2(aq)

• 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

A + BC B + AC

Activity Series – lists metals in order of decreasing reactivity (p.333)

Reactive metals will replace any metal listed below it in the activity series

If the metal is below, no reaction occurs Halogen(7A) can replace other halogens

that are below it in the periodic table

2K(s) + 2H2O(l)

Zn(s) + Cu(NO3)2(aq)

Cu(s) + Al2O3(aq)

Br2(aq) + 2NaI(aq)

Br2(aq) + NaCl

2K(s) + 2H2O(l) 2KOH(aq) + H2(g)

Zn(s) + Cu(NO3)2(aq) Cu(s) + Zn(NO3)2(aq)

Cu(s) + Al2O3(aq) No reaction

Br2(aq) + 2NaI(aq) 2NaBr(aq) + I2(aq)

Br2(aq) + NaCl No reaction

Two compounds undergo a “change of partners”

Two compounds react by exchanging atoms to produce two new compounds

AB + CD AD + CB

Double-displacement reaction Exchange of positive ions Occur in aqueous solutionTo occur: 1. One of the products is slightly soluble

and a precipitates forms2. One product is a gas3. One of the products is a molecular

compound, like water

AB + CD AD + CB

Acid + base water and salt

HCl(aq)+NaOH(aq) NaCl(aq)+H2O(l)

Formation of solid lead chloride from lead nitrate and sodium chloride

Pb(NO3)2(aq) + 2NaCl(aq) PbCl2(s) + 2NaNO3(aq)

Chemical change in a solution that results in one or more insoluble products

Solubility Rules (p.344)1. salts of alkali metals and ammonia soluble2. nitrate salts and chlorate salts soluble3. sulfate salts, except compounds with Pb, Ag,

Hg, Ba, Sr, and Ca soluble4. Chloride salts, except with Ag, Pb, and Hg

soluble5. carbonates, phosphates, chromates, sulfides,

and hydroxides most are insoluble

Predicting Whether Precipitation Will Occur

• Recombine the ionic compounds to have them exchange partners

• Examine the new compounds formed and determine if any are insoluble

• Any insoluble salt will be the precipitate

Pb(NO3)2(aq) + NaCl(aq)

PbCl2 (?) + NaNO3 ( ?)(s) (aq)

Predict Whether These Reactions Form Precipitates

Potassium chloride and silver nitrate

Potassium acetate and silver nitrate

Predict Whether These Reactions Form Precipitates

Potassium chloride and silver nitrate KCl(aq) + AgNO3(aq) KNO3(aq) + AgCl (s)

Potassium acetate and silver nitrate KC2H3O2 + AgNO3(aq) KNO3(aq) +

AgC2H3O2(s)

Reactions with oxygen generally release energy in the form of light or heat

Combustion

Reactants: Oxygen and a hydrocarbons

Products: CO2 and H2O

◦Combustion of natural gas

CH4+2O2CO2+2H2O

•Rusting or corrosion of iron

4Fe + 3O2 2Fe2O3