Chemical Reactions Types of Reactions 5 Types of

Chemical Reactions Types of Reactions

5 Types of Reactions ►Synthesis or Combination ►Decompostion ►Single Replacement ►Double Replacement ►Combustion

Synthesis or Combination Reaction ►Two or more substances combine to form another substance § Example: A + B AB ► 2 H 2 (g) + O 2 (g) 2 H 2 O (g)

Decomposition Reaction ►One substance breaks down or decomposes into two or more simpler substances § Example: AB A + B ► 2 H 2 O 2 H 2 + O 2 § Just the opposite of a synthesis reaction

Single Replacement Reaction ►Occurs when one element replaces another in a compound § Example: AB + C AC + B ►Ba (cr) + Fe. Br 2(aq) Ba. Br 2 (aq) + Fe (cr)

Double Replacement Reaction ► Takes place if a precipitate, water, or a gas forms when two ionic compounds in solution are combined § A precipitate is an insoluble compound formed during this type of reaction § Example: AB + CD AC + BD ►Ag. NO 3 (aq) + Na. Cl (aq) Ag. Cl (cr) + Na. NO 3 (aq)

Combustion Reaction ►A chemical change in which an element or a compound reacts with oxygen often producing energy in the form of heat and light ► Often the other reactant is a hydrocarbon which is a compound composed of hydrogen and carbon ► The products of a combustion reaction are usually CO 2 and H 2 O

Example ► 2 C 8 H 18(l) + 25 O 2(g) 16 CO 2(g) + 18 H 2 O(l) ► Notice the reactants and products § Reactants – Hydrocarbon reacting with Oxygen § Products – CO 2 and H 2 O ► Is this a combustion reaction § 2 Mg(s) + O 2(g) 2 Mg. O (s) ►Yes, because it reacts with oxygen producing heat and light ►It can also be classified as a synthesis or combination reaction

Energy and Chemical Reactions ►In all chemical reactions, energy is either released or absorbed § Bonds must be broken or formed ►To break bonds energy is required ►To form bonds energy is released

Exothermic Reaction ► In many chemical reactions, less energy is required to break the original bonds than is released with the formation of new bonds § Heat is given off ►Examples: ►Reactants Burning of wood; Explosion Products + Energy

Endothermic Reaction ► More energy is required to break the original chemical bonds than is given off. § Heat is absorbed so the container feels colder § Reactants + Energy Products

What type of reaction? ► 2 Na. Br + 1 Ca(OH)2 2 Ca. Br 2 + 2 Na. OH ► 2 NH 3+ 1 H 2 SO 4 1 (NH 4)2 SO 4 ► 3 Pb + 3 H 3 PO 4 3 H 2 + 1 Pb 3(PO 4)2