Analytical ChemistryHard
Question
Select the correct statement(s).
Options
A.In group III, Fe3+ and Cr3+ can be differentiated by increasing NH4+ ion concentration
B.In Vth group, Na2CO3 is added to precipitate out only the carbonates of Ba2+, Sr2+ and Ca2+.
C.Like brown ring test, diphenylamine test is given only by salts containing NO3-.
D.Sodium chloride on heating with aqueous solution of K2Cr2O7 and concentrated H2SO4 produces deep red vapours.
Solution
(A) Cr3+ + 3NH3 + 3H2O → Cr(OH)3↓ + 3NH4+
The reaction is reversible; on addition of NH4+, shifts to backward direction. Thus if excess of NH4+ salt is added, then precipitation of Cr(OH)3 will not take place. However, because of very small ksp of iron (III) hydroxide complete precipitation will take place even in the presence of ammonium salts. (ksp = 3.8 × 10-38)
(C) The oxidising anions like MnO4-, Cr2O72-, ClO4-, etc., also respond to this test.
(D) CrO2Cl2 + 2H2O → H2CrO4 (aq) + 2HCl.
The reaction is reversible; on addition of NH4+, shifts to backward direction. Thus if excess of NH4+ salt is added, then precipitation of Cr(OH)3 will not take place. However, because of very small ksp of iron (III) hydroxide complete precipitation will take place even in the presence of ammonium salts. (ksp = 3.8 × 10-38)
(C) The oxidising anions like MnO4-, Cr2O72-, ClO4-, etc., also respond to this test.
(D) CrO2Cl2 + 2H2O → H2CrO4 (aq) + 2HCl.
Create a free account to view solution
View Solution FreeMore Analytical Chemistry Questions
If crimson flame is given when an inorganic mixture is tested by flame test, it may be due to the presence of...The composition of golden spangles is :...Solution of a salt in dilute H2SO4 or acetic acid produces deep blue colour with starch iodide solution. The salt contai...Chromyl chloride vapours are dissolved in water and acetic acid and barium acetate solution is added, then:...In the fourth group, white precipitate of Mn(OH)2 on heating with PbO2 and concentrated HNO3 gives red-violet (purple) c...