The chemical reaction that are used in the anion spot tests in
this experiment are the most part simple precipitation or acid-base
reactions. Given the information in each test procedure, try to
write the net ionic equation for the key reaction in each
test.
a. CO3 2-
b. SO4 2-
c. PO4 3- (Reactions are HPO4 2-, NH4+, MoO4 2-. and H+; products
are (NH4)3PO4* 12 MoO3 and H2O; no oxidation or reduction
occurs.)
d. SO3 -2
e. SCN-
f. Cl-
g. NO3- (Take as reactants Al and NO3-; as products NH3 and AlO2-;
final equation also
contains OH- and H2O as reactants.)
Anion spot test reactions are as follows,
a. CO3^2-
add a drop of BaCl2
Ba2+ + CO3^2- ----> BaCO3 (white ppt)
confirms presence of CO3^2-
b. SO4^2-
Add BaCl2 solution to the spot,
Ba2+ + SO4^2- ---> BaSO4 (white ppt)
confirms presence of SO4^2-. The ppt does not dissolve on addition of HCl.
c. PO4^3-
Add acdified ammonium molybdate
HPO4^2- + 12MoO4^2- + 23H+ + 3NH4+ ---> (NH4)3PO4.12MoO3 (yellow ppt) + 12H2O
d. SO3^2-
Add BaCl2,
Ba2+ + SO3^2- ---> BaSO3 (white ppt)
confirms presence of SO3^2-. The ppt dissolves on addition of HCl.
e. SCN-
Add acidified FeCl3
Fe3+ + SCN- ---> [Fe(SCN)]2+ (blood red ppt)
f. Cl-
Add a drop of acidified AgNO3
Ag+ + Cl- ---> AgCl (white ppt)
confirms presence of Cl-
g. NO3-
Add base and Al,
8Al + 3NO3- + 5OH- ---> 3NH3 + 8AlO2-
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