|In Redox reactions:
1. one element GRABS electron(s)
2. the other GIVES UP electron(s)
-- The element that grabs electrons (often
oxygen) is said to be a good OXIDIZER.
OVERALL Reaction: 2 Ag + S = Ag2S
Silver gives up electrons to Sulfur
Ag (elemental silver or (s)) ->
Ag+ (ionic silver (aq)) - an electron(e-)
S (elemental sulfur(s)) -> S2-
(ionic sulfur (aq)) + 2 e-
s= solid aq = aqueous
1. There must always be a pair of reacting
2. One gives, one gets.
The electrons will flow from those with
weakest hold on the electrons to those with the strongest hold.
There is a list compiled by experimentation to determine which elements
gives to which and which takes from which.
At least for metals when a metal has all
its electrons it is a solid. When it loses its electrons it
goes into water solution as an ION.
There must be some kind of "salt bridge"
which is nothing more than water with some "salts"
connecting the two chambers containing the elements. Everything starts
with a 0 zero charge, but ions wont move freely in distilled water, they
need an established ionic or salty water.
Redox reactions will not occur just by
putting two pieces of metal on top of each other. There must be moisture
and salts of some kind. This is the reason that salting streets in winter
results in cars rusting so badly. In southern states that dont need
to salt cars do not readily rust.
|Classic example of a redox reaction =
When a zinc (Zn) bar is inserted in a salt
solution, Zn tends to loose electrons according to the reaction,
Zn = Zn2+ + 2 e-.
Copper (Cu) is inserted in a copper salt
solution, copper tends to loose electrons according to the reaction,
Cu = Cu2+ + 2 e-.
However, Zn wants to loose electrons
copper, so when the two cells are connected by a salt bridge and a wire,
an electrical current occurs as electrons flow from the zinc chamber
to where the copper ions (Cu2+) are and copper by gaining electrons become
copper metal. This is a galvanic cell or battery.