Chemical Reactions: Synthesis, Decomposition, Displacement, and Combustion, Slides of Chemistry

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TYPES OF

CHEMICAL REACTIONS

To react or not to react? THAT is

the question!

 Chemical changes are a result of chemical reactions.

 All chemical reactions involve a change in substances and a change in energy.

 Neither matter or energy is created or destroyed in a chemical reaction---only changed.

Chemical Reactions

#1 Synthesis Reactions

 Synthesis = combine = put together

 Two or more simple substances combine to form a more complex substance.

 The reaction through the equation:

reactant + reactant -------> product A + B -------> AB

 Ca + O 2 CaO

 SO 3 + H 2 O  H 2 SO 4

 For example, simple hydrogen gas combined with simple oxygen gas can produce a more complex substance— water!

 The chemical equation for this synthesis reaction is:

2H 2 + O 2  2H 2 O

#1 Synthesis Reactions

 metal + oxygen  metal oxide

4Fe(s) + 3O2(g)  2Fe 2 O3(s)

 nonmetal + oxygen  nonmetal oxide

S(s) + O2(g)  SO2(g)

 metal oxide + water  metallic hydroxide

MgO(s) + H 2 O(l)  2Mg(OH)2(s)

#1 Synthesis Reactions

 nonmetallic oxide + water  acid

SO3(g) + H 2 O(l)  H 2 SO4(aq)

 metal + nonmetal  salt

2Na(s) + Cl2(g)  2NaCl(s)

#1 Synthesis Reactions

 In a decomposition reaction a more complex substance breaks down into its more simple parts.

 One reactant yields 2 or more products. Basically, synthesis and decomposition reactions are opposites. reactant -------> product + product AB -------> A + B

#2 Decomposition Reactions

 For example, water can be broken down into hydrogen gas and oxygen gas.

 The chemical equation for this decomposition reaction looks like:

2H 2 O  2H 2 + O 2

#2 Decomposition Reactions

 The explosion of a dynamite is an example of a decomposition reaction.

• When suitably activated, a highly exothermic reaction occurs in which large amounts of gaseous products form.

 Nitroglycerin, which can be activated merely by shaking, decomposes as follows: 4C 3 H 5 (NO 3 )3(l)  6N2 (g) + 12CO2(g) + 10H 20 (g) + O2(g)

#2 Decomposition Reactions

 The egg (the reactant), which contained the turtle at one time, now has opened and the turtle (product) and egg shell (product) are now two separate substances.

#2 Decomposition Reactions

 Some oxides, when heated, decompose.

2HgO(s)  2Hg(l) + O2(g)

 Some acids, when heated, decompose into nonmetallic oxides and water. H 2 SO4(s)  H 2 O(l) + SO3(g)

#2 Decomposition Reactions

#3 Single Displacement

 In a single displacement reaction a single uncombined element replaces another in a compound.

• Reactants must be an element and a compound.
• Products will be a different element and a different compound.

 Two reactants yield two products. reactant + reactant ---------> product + product AB + C -------> AC + B

• Na + KCl  K + NaCl
• F 2 + LiCl  LiF + Cl 2

#3 Single Replacement

 Metals replace metals (and hydrogen)

• K + AlN 
• Zn + HCl 

 Think of water as HOH

 Metals replace one of the H’s, combine with hydroxide.

• Na + HOH 

 Notice, the guy in the orange shirt steals the date of the other guy.  So, a part of one of the reactants trades places and is in a different place among the products.

#3 Single Displacement