Chemistry Chapter 8

1
Chemistry Chapter 8

• Chemical Equations and Reactions

2
Synthesis (Composition) Reactions
Two or more substances combine to form a new
compound.
A X ? AX

• Reaction of elements with oxygen and sulfur
• Reactions of metals with Halogens
• Synthesis Reactions with Oxides
• There are others not covered here!

3
Decomposition Reactions
A single compound undergoes a reaction that
produces two or more simpler substances
AX ? A X

• Decomposition of
• Binary compounds H2O(l ) ? 2H2(g) O2(g)
• Metal carbonates CaCO3(s) ? CaO(s) CO2(g)
• Metal hydroxides Ca(OH)2(s) ? CaO(s) H2O(g)
• Metal chlorates 2KClO3(s) ? 2KCl(s) 3O2(g)
• Oxyacids H2CO3(aq) ? CO2(g) H2O(l
  )

4
Single Replacement Reactions
A BX ? AX B
BX Y ? BY X
Replacement of

• Metals by another metal
• Hydrogen in water by a metal
• Hydrogen in an acid by a metal
• Halogens by more active halogens

5
The Activity Series of the Metals

• Lithium
• Potassium
• Calcium
• Sodium
• Magnesium
• Aluminum
• Zinc
• Chromium
• Iron
• Nickel
• Lead
• Hydrogen
• Bismuth
• Copper
• Mercury
• Silver
• Platinum
• Gold

Metals can replace other metals provided that
they are above the metal that they are trying to
replace.
Metals above hydrogen can replace hydrogen in
acids.
Metals from sodium upward can replace hydrogen in
water
6
The Activity Series of the Halogens

• Fluorine
• Chlorine
• Bromine
• Iodine

Halogens can replace other halogens in
compounds, provided that they are above the
halogen that they are trying to replace.
2NaCl(s) F2(g) ?
2NaF(s) Cl2(g)
???
MgCl2(s) Br2(g) ?
???
No Reaction
7
Double Replacement Reactions
The ions of two compounds exchange places in
an aqueous solution to form two new compounds.
AX BY ? AY BX
One of the compounds formed is usually a
precipitate, an insoluble gas that bubbles out
of solution, or a molecular compound, usually
water.
8
Combustion Reactions
A substance combines with oxygen, releasing a
large amount of energy in the form of light and
heat.

• Reactive elements combine with oxygen

P4(s) 5O2(g) ? P4O10(s)
(This is also a synthesis reaction)

• The burning of natural gas, wood, gasoline

C3H8(g) 5O2(g) ? 3CO2(g) 4H2O(g)