Confirmatory tests and coloured precipitates

27 questions on Confirmatory tests and coloured precipitates from the Qualitative Analysis: Cations chapter: 5 NEET level, 11 JEE Main, 11 JEE Advanced. Each one opens with its answer and solution.

• Addition of aqueous KSCN to a solution containing Fe^3+ produces NEET level
• When aqueous ammonia is added to a solution of Cu^2+ first dropwise and then in excess, the final observation is NEET level
• Dimethylglyoxime in ammoniacal medium gives a characteristic precipitate with Ni^2+. Its colour is NEET level
• Which of the following sulphides is yellow in colour? NEET level
• Among the sulphides of group IV, the one that is white is NEET level
• Aqueous K4[Fe(CN)6] is added separately to solutions of Cu^2+ and Zn^2+. The precipitates formed are, respectively, JEE Main level
• A pale green solution gives a deep blue precipitate with K3[Fe(CN)6] but no red coloration with KSCN before oxidation. The ion present is JEE Main level
• A clear solution of bismuth nitrate in dilute nitric acid turns milky white when poured into a large volume of water. The responsible species and reaction is JEE Main level
• Excess KCN is added to a mixture containing Cu^2+ and Cd^2+ and H2S is then passed. The precipitate obtained is JEE Main level
• A colourless solution gives a white gelatinous precipitate with NaOH that dissolves in excess NaOH. With NH4OH (in the presence of NH4Cl) the white precipitate ... JEE Main level
• A green solution of Cr^3+ is made strongly alkaline and warmed with H2O2 until the colour turns yellow. How many moles of H2O2 are consumed per mole of Cr^3+? JEE Main level
• A borax bead heated in the oxidising flame with a trace of an unknown salt becomes violet (amethyst) when hot and cold. The metal is JEE Main level
• In the test for Mn^2+ with solid NaBiO3, the solution is acidified with nitric acid and not hydrochloric acid because JEE Main level
• Rinmann's green, obtained when a zinc salt is moistened with Co(NO3)2 and ignited, is JEE Main level
• Which of the following statements about the nickel dimethylglyoximate complex, [Ni(DMG)2], are correct? JEE Main level
• In the thiocyanate test for Co^2+ (blue colour extracted into amyl alcohol), interference from Fe^3+ is removed by adding JEE Main level
• A white precipitate from dilute HCl dissolves on boiling with water. The hot solution gives a yellow precipitate with K2CrO4. Which description of the yellow pr... JEE Advanced level
• A black sulphide X from group II (precipitated with H2S in 0.3 M HCl) does not dissolve in yellow ammonium sulphide but dissolves in hot dilute HNO3. The nitrat... JEE Advanced level
• On treating a chromium(III) solution with NaOH and H2O2 and then acidifying with dilute H2SO4, adding more H2O2 and shaking with ether, a blue colour develops i... JEE Advanced level
• A mixture of group IV sulphides (ZnS, MnS, NiS, CoS) is treated with cold dilute HCl. The residue is dissolved in aqua regia, the solution is made ammoniacal an... JEE Advanced level
• What minimum mass of K3[Fe(CN)6] is needed to convert all the iron in a solution containing 0.30 mol of Fe^2+ into Turnbull's blue, Fe3[Fe(CN)6]2? (K 39, Fe 56,... JEE Advanced level
• Excess KCN added to Cu^2+ reduces it to copper(I) with evolution of cyanogen: 2Cu^2+ + 8CN- -> 2[Cu(CN)3]^2- + (CN)2. How many moles of KCN are consumed per mol... JEE Advanced level
• Which of the following sulphides dissolve in yellow ammonium sulphide (or ammonium polysulphide) forming thio-anions? JEE Advanced level
• Which statements about the tests for Al^3+ are correct? JEE Advanced level
• Which statements about the oxidation of chromium(III) in alkaline hydrogen peroxide are correct? JEE Advanced level
• Which statements about Zn^2+ are correct? JEE Advanced level
• A solution is 0.020 M in Zn^2+ and is saturated with H2S ([H2S] = 0.10 M). For H2S take K_a1K_a2 = 1.0x10^-21 and for ZnS take K_sp = 4.0x10^-22. Find the pH of... JEE Advanced level