chapter 8 section 2 continued

DECOMPOSITION REACTIONS
-in a decomp reaction, a single compound becomes two or ore simpler substances
-opposite of synthesis
-represented AX-->A + X
-AX is a compound
- A and X can be elements or compounds
- always smaller than AX

-decomp reactions with electricity are called hydrolysis
-2H2O-electricity-> 2H2 + O2
-Oxides of less reactive metals decompose into their elements when heated

-Decomp of acids
-certain acids decompose into nonmetal oxides and water
-carbonic acid readily dec0mposes at room temperature int CO2 and water

SINGLE-REPLACEMENT REACTIONS
-one element replaces a similar elemen i a compound
-many take place in aqueous solution
-A+BX-->AX+B or Y + BX -->BY + x
-most-active metals, Group 1, react with H2O to produce metal hydroxides and hydrogen
-less-active metals, example Iron, react with stea to form a metal oxide and hydrogen gas
-more-active metals react with certain acidic solutions, replacing hydrogen in acids
-products are a metal compound and hydrogen gas

-displacement of halogens
-fluorine is the most-active halogen
-in Group 17. each element ca replace any element below it, but none above it

DOUBLE-DISPLACEMENT REACTIONS
-ions of two compounds exchange place is an aqueous solution to from two new substances
-one of the compounds formed is usually a precipitate, gas, or a molecular compound
-AX+BY --> AY+BX
-A,X,B, &Y are ions
-AY & BX are ionic or molecular compounds

-formation of a precipitate
-cations of one compound combine anions of another
-form insoluble or slightly soluble compounds

COMBUSTION
-substances combine with oxygen, releasing large amounts of light and heat
-2H2+O2-->2H20
-C3H8+5O2-->3CO2+4H2O

**remember that the homework will be graded on correctness**