The chemical reaction that are used in the anion spot tests in this experiment a

Question

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.)

Explanation / Answer

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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