2. Calculate the concentration of free
Cr
3+
ion when 0.010 mol of
Cr(NO
3
)
3
is dissolved in a litre of solution buffered at pH = 10.0, and the
K
f
for
Cr(OH)
4
-
= 8.0 x 10
29
.
Which equation is the appropriate equilibrium equation involved?
a)
Cr(NO
3
)
3
(aq)
Cr
3+
(aq) + 3 NO
3
-
(aq)
b)
Cr(NO
3
)
3
(aq) + OH
-
(aq)
Cr
3+
(aq) + OH(NO
3
)
3
4-
(aq)
c)
Cr
3+
(aq) + 3 NO
3
-
(aq)
Cr(NO
3
)
3
(aq)
d)
Cr
3+
(aq) + 4 OH
-
(aq)
Cr(OH)
4
-
(aq)
