Group reagents and group separation logic

27 questions on Group reagents and group separation logic from the Qualitative Analysis: Cations chapter: 5 NEET level, 10 JEE Main, 12 JEE Advanced. Each one opens with its answer and solution.

• Which reagent is used as the group reagent to precipitate the group I cations (such as Ag+ and Pb^2+) from the original solution? NEET level
• The group reagent for the precipitation of group III cations (Fe^3+, Al^3+, Cr^3+) as hydroxides is NEET level
• Solid NH4Cl is added before NH4OH in the group III analysis mainly because it NEET level
• Group V cations (Ba^2+, Sr^2+, Ca^2+) are precipitated as carbonates using NEET level
• Among the following sulphides precipitated in group IV (by H2S in ammoniacal medium), the white one is NEET level
• Group II cations are precipitated by passing H2S into the solution made about 0.3 M in HCl. The role of the HCl is to JEE Main level
• Zn^2+ is not precipitated when H2S is passed into a solution containing dilute HCl, because JEE Main level
• The filtrate from group II is boiled before the group III reagent is added. The main purpose is to JEE Main level
• Pb^2+ is reported both in group I and in group II because JEE Main level
• Assertion (A): As2S3 dissolves in yellow ammonium sulphide but CdS does not. Reason (R): As2S3 is an acidic sulphide that forms a soluble thio-anion with sulphi... JEE Main level
• Match the group in Column I with its reagent in Column II. Column I: (P) Group I, (Q) Group III, (R) Group IV, (S) Group V. Column II: (1) NH4Cl + NH4OH, (2) (N... JEE Main level
• A white crystalline precipitate forms when Na2HPO4 is added to a solution containing NH4Cl and excess NH4OH (after groups I to V have been removed). The precipi... JEE Main level
• The test for NH4+ is always performed on a fresh portion of the original solution, not on the filtrates, because JEE Main level
• NH4Cl and NH4OH must be present when (NH4)2CO3 is added in group V, mainly to JEE Main level
• Among the following hydroxides, the one that is precipitated when NH4OH is added to a solution containing excess NH4Cl is JEE Main level
• A solution is 0.015 M in Zn^2+ and is kept saturated with H2S ([H2S] = 0.10 M throughout). For the overall ionisation H2S <=> 2H+ + S^2- take K = [H+]^2[S^2-]/[... JEE Advanced level
• Select the correct statements about the use of HCl and H2S in the group II separation. JEE Advanced level
• For the group III separation, which of the following statements are correct? JEE Advanced level
• The filtrate from group II contains Fe^2+ (formed by reduction with H2S) and is to be analysed for group III. Select the correct statements. JEE Advanced level
• A solution is 0.30 M in HCl, saturated with H2S (0.10 M), and contains each of Cd^2+, Cu^2+, Zn^2+ and Ni^2+ at 0.010 M. Use K = [H+]^2[S^2-]/[H2S] = 1.0x10^-21... JEE Advanced level
• Regarding the group VI cation Mg^2+, which statements are correct? JEE Advanced level
• Select the correct statements about the test for ammonium ion. JEE Advanced level
• A blue solution of salt X gives no precipitate with dilute HCl. Passing H2S through the acidified solution gives a black precipitate Y, which dissolves in hot d... JEE Advanced level
• A solution is 0.020 M in Zn^2+ and 0.50 M in HCl, and is saturated with H2S (0.10 M). Take K = [H+]^2[S^2-]/[H2S] = 1.0x10^-21 and K_sp(ZnS) = 3.0x10^-22 (negle... JEE Advanced level
• The group II filtrate (containing Fe^3+ reduced to Fe^2+, Zn^2+ and Mg^2+) is treated with NH4Cl and NH4OH without boiling off the dissolved H2S. The solid obta... JEE Advanced level
• A solution is 0.0100 M in Pb^2+. Dilute HCl is added so that the equilibrium chloride concentration is 0.10 M (assume it is unchanged by precipitation). With K_... JEE Advanced level
• A solution contains 0.10 mol Cu^2+ and 0.10 mol Cd^2+. It is treated with just enough KCN to convert copper to [Cu(CN)4]^3- (with (CN)2 as the oxidation product... JEE Advanced level