Aqueous Solutions Page 3
ADVERTISEMENT
1
2
3
4Selective Precipitation
Some ionic compounds have very low solubility and will form a solid precipitate when the
two ions are mixed together in a solution.
The solubility chart is used to predict whether a precipitate will form or not.
EX. Demonstrate the mixing together of lead (II) nitrate and potassium iodide.
Pb(NO
)
+
2 KI
2KNO
+ PbI
3
2 (aq)
(aq)
3 (aq)
2 (s)
2+
+
+
-
Pb
K
K
NO
(aq)
(aq)
(aq)
3
(aq)
+
-
-
NO
I
PbI
3
(aq)
(aq)
2 (s)
2+
+
+
-
Pb
K
K
NO
(aq)
(aq)
(aq)
3
(aq)
-
-
NO
I
PbI
3
(aq)
(aq)
2 (s)
Selective precipitation can be used to confirm the presence or absence of a particular ion in
an unknown solution.
To test for a certain ion in a solution, you must an oppositely charged ion to it that would
react to produce an insoluble precipitate if the original ion was indeed present.
EX. How could you test for the presence of Br
-
?
(aq)
EX. How could you test for the presence of Mg
2+
?
(aq)
If you are testing for more than one ion, you must ensure that only one possible precipitate
can be produced in each step.
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education