ABSTRACT
Chemical reactions can be classified according to the number of phases involved. A reaction that is confined to a single phase is termed
homogeneous
. An example of this type of reaction is the combustion of methane:
CH
(g) + 2O
(g) = CO
(g) + 2H
O(g) (9.1)
Another example of a homogeneous reaction is the transfer of electrons between ions in aqueous solution, as in the reduction of tetravalent plutonium by ferrous ions:
Pu
(aq) + Fe
(aq) = Pu
(aq) + Fe
(aq) (9.2)
The medium in which the reaction occurs is designated in parentheses: g for the gas phase; aq for an aqueous solution; L for a pure, nonaqueous liquid (e.g., a molten metal); soln for a nonaqueous solution; and s for a solid phase. Discussion of aqueous ionic chemical equilibrium is deferred until Chapter 10.
