Decomposition reactions involve the splitting apart of a compound into simpler element.
The general formula is:
XY → X + Y
or
compound → element + element
This is analogous to the man and a woman breaking up.
Some lone elements are “special” and will be found as diatomics or polyatomics: H2, O2, N2, F2, Cl2, Br2, I2, P4, S8.
All other elements are monatomics: Fe, Ca, Li, etc.
Remember: Elements combined in compounds use their valences to determined the ratios in a compound.
Practice Questions:
For each of the following (a) complete the word equation, (b) create a balanced equation.
(a) hydrogen oxide →
(b) nitrogen triiodide →
(c) calcium sulfide →
Answers:
(a) hydrogen oxide → hydrogen + oxygen
2H2O → 2H2 + O2
(b) nitrogen triiodide → nitrogen + iodine
2NI3 → N2 + 3I2
(c) calcium sulfide → calcium + sulfur
8CaS → 8Ca + S8
Combustion Reactions
Combustion reactions involve the burning of a hydrocarbon in oxygen to produce carbon dioxide and water.
The general formula is:
hydrocarbon + oxygen → carbon dioxide + water
An example is:
CH4 + 2O2 → CO2 + 2H2O
Homework:
Do the "Decomposition Reactions" at the bottom of the page.
Answers:
