Group IV cations (Zn, Mn, Ni, Co)

27 questions on Group IV cations (Zn, Mn, Ni, Co) from the Qualitative Analysis: Cations chapter: 5 NEET level, 11 JEE Main, 11 JEE Advanced. Each one opens with its answer and solution.

• The group reagent for group IV cations (Zn^2+, Mn^2+, Ni^2+, Co^2+) is NEET level
• Among the sulphides ZnS, MnS, NiS and CoS, the one that is white is NEET level
• Dimethylglyoxime in ammoniacal solution gives a characteristic precipitate with Ni^2+ of colour NEET level
• Among the following, the hydroxide that dissolves in excess NaOH to give a clear solution is NEET level
• The colour of manganese(II) sulphide precipitated in group IV is NEET level
• A pale-pink solution is warmed with NaBiO3 and dilute HNO3. The colour observed and the reason why HNO3 rather than HCl is used are JEE Main level
• When aqueous Co^2+ is treated with excess solid NH4SCN and shaken with amyl alcohol, the organic layer turns blue. The geometry of the blue species [Co(NCS)4]^2... JEE Main level
• In the red complex Ni(DMG)2, which statement is correct? JEE Main level
• A colourless solution gives a white precipitate with NaOH. The precipitate dissolves in excess NaOH and also in excess NH4OH. The cation is JEE Main level
• A paper ash containing the precipitate is moistened with Co(NO3)2 and ignited. Which pair of cation and ash colour is correct? JEE Main level
• White Mn(OH)2, exposed to air, slowly turns brown. This is because manganese is oxidised from JEE Main level
• Assertion (A): NiS and CoS are not precipitated by H2S in dilute HCl, yet once precipitated in ammoniacal medium they do not redissolve in cold dilute HCl. Reas... JEE Main level
• Match the cation (List I) with the reagent/observation (List II). List I: (P) Ni^2+, (Q) Co^2+, (R) Zn^2+, (S) Mn^2+. List II: (1) NaBiO3/HNO3 gives purple solu... JEE Main level
• A colourless solution gives a white precipitate with H2S in ammoniacal medium that dissolves in dilute HCl. The ion is colourless because JEE Main level
• Which of the following statements about the group IV sulphides are correct? JEE Main level
• Which reagents can be used to distinguish Ni^2+ from Co^2+ in the same dilute solution? JEE Main level
• A solution contains 0.010 M each of Cu^2+, Cd^2+, Zn^2+ and Ni^2+ and is saturated with H2S (0.10 M) at [H^+] = 0.30 M. Use K_a1K_a2 = 1.1x10^-21 for H2S and K_... JEE Advanced level
• A solution is 0.010 M in Mn^2+ and contains 0.10 M NH3. Take K_b(NH3) = 1.8x10^-5 and K_sp[Mn(OH)2] = 2.0x10^-13. Does Mn(OH)2 precipitate (i) with no NH4Cl add... JEE Advanced level
• A pale-pink solution gives a white precipitate with NaOH that browns in air. How many moles of NaBiO3 are required to oxidise one mole of the cation completely ... JEE Advanced level
• A green solution gives a green precipitate with NaOH and a blue solution in excess NH3. With dimethylglyoxime it gives a red precipitate. For the red complex, t... JEE Advanced level
• A pink solution gives a blue organic layer with NH4SCN/amyl alcohol and a yellow precipitate with KNO2 and acetic acid. For the yellow compound K3[Co(NO2)6], th... JEE Advanced level
• In group IV, white zinc ferrocyanide is obtained from a solution of Zn^2+ with excess K4[Fe(CN)6] as K2Zn3[Fe(CN)6]2. How many moles of K4[Fe(CN)6] are used per... JEE Advanced level
• Select the correct statements about nickel and cobalt. JEE Advanced level
• Select the correct statements about manganese. JEE Advanced level
• Select the correct statements about the group IV separation. JEE Advanced level
• A mixture of Zn(OH)2, Ni(OH)2 and Mn(OH)2 is shaken with excess NaOH and filtered. Select the correct statements. JEE Advanced level
• A solution is 0.040 M in Zn^2+ and saturated with H2S ([H2S] = 0.10 M). Take K_a1K_a2 = 1.1x10^-21 for H2S and K_sp(ZnS) = 2.5x10^-22. Calculate the minimum [H^... JEE Advanced level