Page 146 - Basic physical chemistry for the atmospheric sciences

1 3 2 Basic physical chemistry

the silver solution and the gold in the gold solution? (One equiv. of
1
g
silver = 0 8 . )
o
o
Solution. The number f equivalents f silver liberated b y the pas­
sage of the electric charge is 0. 72/1 0 8 = 0.0067. Since this same electric
charge will release 0.0067 equiv. of gold, 0 . 4 4 g of gold is the same as
0.0067 equiv. of gold. Therefore, l gram-equivalent weight of
gold = 0.44/0. 0 067 = 66. Let the oxidation state of the silver in solution
be n, then

Agn + (aq) + ne - � Ag(s)
Therefore,
l mole of silver
I equiv. of silver = -----­
n
or,

l mole of silver 1 0 8
n = - - = l
1 equiv. of silver 1 0 8
Similarly, if the oxidation state of the gold is m
l mole of gold 1 9 7
m = - = 3
i
1 equ v . of gold 66
(Note: A given oxidant or reductant may have more than one equiva­
lence, depending on the reaction involved. )

Exercises
6. 1 1 . Answer, interpret, or explain the following in light of the
pr n ciples presented in this chapter.
i
(a) Hydrogen peroxide, H20 (g), is generally used com­
2
mercially in the form of a 30% aqueous solution. The
bottle contains the warning: "Contact with other mate­
rials may cause fire. If swallowed , give water or milk
to dri k . "
n
2
2
(b) The reaction Zn(s) + C u + ( aq) � Zn + ( aq) + Cu(s) is an
oxidation-reduction reaction, even though oxygen is
not involved.
(c) Sulfur dioxide gas, S02(g) , is emitted into the air when
sulfur-containing coal or gas is burned in electric power
plants. The S02(g) dissolves in cloud drops to form