Chemical reactions

• Evidence of chemical rxns:– Change in enthalpy– Change in color– Formation of a gas– Formation of a ppt

Chemical reaction- represented by an equation

2 C2H2 (g) + 5O2 (g) 4CO2 (g) + 2H2O(l)

Reactants

Products

(aq) a substance dissolved in water

Equations must be balanced

Start with a skeleton eqn

Never change a subscript

Exercises Pg 279 + 282

Synthesis Rxns - 2 or more substances combine

2Na (s) + Cl2 (g) 2NaCl (s)

Element or compound + element or compound compound

Combustion Rxns - oxidation reactions—reacting with oxygen

Oxidation of a hydrocarbon

Produces CO2 (g) + H2O (g)

CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (g)

Single Displacement Rxns - one element displaces another in a compoundBr2 (l) + 2KI (s) 2KBr (aq) + I2 (s)

2Al (cr) + 3ZnCl2 (cr) 2AlCl3 (cr) + 3Zn (cr)

Note that a nonmetal replaces a nonmetal and a metal replaces a metal, charges add

up to zero, and you must use figure 10-10.Element + Compound Element + Compound

Double Displacement Rxns

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

compound + compound compound + compound

Decomposition Rxns - break up into simple substances when energy is supplied(Heat, light, mechanical shock, or

electricity)H2CO3 (aq) H2O(l) + CO2 (g)

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

Compound 2 or more elements or compounds

Rxns in Aqueous Soln’s

– Complete chemical eqn– Complete ionic eqn– Net ionic eqn (exclude spectator ions)

• Rxns that form ppts

Example:Sodium hydroxide and Copper (II) chloride

• Do page 294 33-37

Rxns that form water

• Hydrofluoric acid and calcium hydroxide

Do page 296 38-42

Rxns that form gases

• Hydroiodic acid and potassium sulfide

Do page 299 43-46

Quiz

• Lead (II) nitrate reacts with potassium iodide - Lead (II) iodide forms a ppt

• Write the chemical equation

• Write the complete ionic equation

• Id all spectators

• Write the net ionic equation

Five Types of Chemical Reactions

1. Single Displacement

element + compoundelement + compound

2. Double Displacement

compound AB + compound CDcompound AD +compound CB

3. Decomposition

compoundtwo or more elements or compounds

4. Synthesis

element or compound + element or compound compound

5. Combustion

hydrocarbon + oxygen carbon dioxide + water

Rxns in Aqueous soln’s

• Rxns that form ppts

• Complete eqn

• Complete ionic eqn

Spectator ions

Net ionic eqn

Potassium carbonate and manganese (V) chloride

Rxns that form waterHydrochloric acid and calcium hydroxide

Rxns that form gasesHydroiodic acid and lithium sulfide