Salt Analysis and Qualitative Analysis Exercise # 4

Exercise # 4 [Subjective Type Questions] 1. Which radical of group IVth gives bluish white / white precipitate with excess K4[Fe(CN)6] ? 2. What products are formed ? When : (i) Disodium hydrogen phosphate is added to magnesium sulphate in presence of ammonium chloride and aqueous ammonia. (ii) A solution containing Zn2+ ions is poured in an aqueous ammonia. (iii) Bi(NO3)3 solution is mixed with K and then resulting precipitate is heated with water. (iv) Disodium hydrogen phosphate is boiled with concentrated HNO3 and ammonium molybdate reagent. 3. Complete and balance the following chemical reactions. fused (i) Cu(BO2)2 + C   (ii) AgBr + concentrated NH3  fused (iii) Cr(OH)3 + Na2CO3 + KNO3    (iv) Cu(NO3)2  4. Salt + H2SO4 (dilute)  Coloured vapours which turns starch iodide paper blue. Identify the acid radical and the coloured vapours giving the relevant chemical equations. 5. Which chloride of st group basic radicals turns black on treatment with NH3 ? 6. Which basic radicals form oxo-cations in aqueous solutions ? 7. Complete and balance the following reaction. Ether (i) Na2S + CdCO3  ............... + .............. (ii) CoCl2 + NH4SCN   ............... + ........... 8. A black coloured compound (A) on reaction with dilute H2SO4 gives a gas (B) which on passing in a solution of an acid (C) gives a white turbidity (D). Gas (B) when passed in an acidified solution of a compound (E) gives a precipitate (F) soluble in dilute HNO3. After boiling this solution when an excess of NH4OH is added, a intense blue coloured compound (G) is formed. To this solution on addition of acetic acid and aqueous K4[Fe(CN)6] a chocolate brown precipitate (H) is obtained. On addition of an aqueous solution of BaCl2 to an aqueous solution of (E) a white precipitate insoluble in dilute HCl is obtained. Identify the compounds from (A) to (H). 9. A compound (A) is greenish crystalline salt, which gave the following reactions. (i) Addition of BaCl2 solution to the solution of (A) results in the formation of white precipitate (B) which is insoluble in dilute HCl. (ii) On heating (A), water vapours and two oxides of sulphur (C) and (D) are liberated leaving a red brown residue (E). (iii) (E) dissolves in warm concentrated HCl to give a yellow solution (F). (iv) Solution (F) on treatment with thiocyanate ions gives blood red coloured compound (G). Identify the compounds from (A) to (G). 10. (i) A blue coloured compound (A) on heating gives two product (B) & (C). (ii) A metal (D) is deposited on passing hydrogen through heated (B). (iii) The solution of (B) in HCl on treatment with the [Fe(CN)6]4– gives a chocolate brown coloured precipitate of compound (E). (iv) (C) turns lime water milky which disappears on continuous passage of (C) forming a compound (F). Identify (A) to (F) and give chemical equations for the reactions at step (i) to (iv). SALT ANALYSIS AND QUALITATIVE ANALYSIS 11. Why in cobalt nitrate test for aluminium salts, excess of cobalt nitrate should not be added ? 12. AgNO 3 NaOH dil H2SO 4 NaOH In the reaction sequence : CrO2Cl2    A    B    C   D Identify [A] to [D]. 13. A white substance (A) reacts with dilute H2SO4 to produce a colourless gas (B) and a colourless solution (C). The reaction between (B) and acidified K2Cr2O7 solution produces a green solution and a slightly coloured precipitate (D). The substance (D) burns in air to produce a gas (E) which reacts with (B) to yield (D) and a colourless liquid. Anhydrous copper sulphate is turned blue on addition of this colourless liquid. Addition of aqueous NH3 or NaOH to (C) produces first a white precipitate which dissolves in the excess of the respective reagent to produce a clear solution in each case. Identify (A), (B), (C), (D) and (E). 14. A mixture of two salts was treated as follows. (i) The mixture was heated with precipitated MnO2 and concentrated H2SO4 when a yellowish green gas was liberated. (ii) The mixture on heating with NaOH solution gave a gas which turned red litmus blue. (iii) Its solution in water gave red colouration with dimethylglyoxime in alkaline solution and white precipitate with K4[Fe(CN)6] in absence of air. (iv) The mixture was boiled with KOH and the liberated gas was bubbled through an alkaline solution of K 2Hg4 to give a brown precipitate. Identify the ions present in the mixture. 15. (i) An aqueous solution of a compound (A) is acidic towards litmus and (A) is sublimed at about 300ºC. (ii) (A) on treatment with an excess of NH4SCN gives a red coloured compound (B) and on treatment with a solution of K4Fe(CN)6 gives a blue coloured compound (C). (iii) (A) on heating with excess of solid K2Cr2O7 in presence of concentrated H2SO4 gives deep red vapour of (D). (iv) On passing vapour of (D) into a solution of NaOH and then adding the solution of acetic and lead acetate, a yellow precipitate of compound (E) is obtained . Identify (A) to (E) and give chemical equations for the reactions at steps (ii) to (iv). 16. What happens when ? (a) To a Zn2+ ions solution faintly acidified with 2M acetic acid, 0.1 mL of 0.25 M CuSO4 solution and 2 mL of ammonium tetrathiocyanatomercurate(II) reagent is added. (b) The above test is performed in absence of CuSO4 solution. 17. 18. Amongst the following, the total number of compounds soluble in concentrated NH3 solution is : (A) Ag2CrO4, (B) Cu(OH)2 . CuSO4, (C) PbSO3, (D) Al(OH)3, (F) Zn3(PO4)2 (G) BaSO4, (H) Bi(OH)2NO3, (I) Mn(OH)2 (E) Ni(OH)2, An alcoholic solution of dimethylglyoxime is added to an aqueous solution of nickel(II) chloride. Slow addition of ammonium hydroxide led to the precipitation of a bright-red coloured metal complex. Find out the number of hydrogen bonds present in the structure of the complex. 19. Fe2+ (aq) + NO 3– (aq) + H2SO4 (conc.)  Brown ring The brown ring is due to the formation of complex, [Fe(H2O)5NO]SO4. What is the oxidation state of iron in the complex ? 20. How many of the following salts impart characteristic colours to the Bunsen flame? NaCl, KCl, CuCl2, BaCl2, CaCl2, SrCl2, ZnCl2, MgCl2, AlCl3 21. How many of the following liberate coloured vapour/gas with concentrated H2SO4? KCl (s) + K2Cr2O7 (s), KNO2 (s), KI(s), KBr(s), KCl(s) KBr (s) + MnO2 (s), KNO3, KCI(s) + MnO2, K2SO3 22. How many of the following pairs of ions can be separated by H2S in dilute HCl? Bi3+ and Sn4+, Al3+ and Hg2+, Cd2+ and Zn2+, Fe3+ and Cu2+, As3+ and Sb3+ 23. An aqueous solution contains Hg2+, Hg22+, Pb2+, Ag+, Bi3+ and Cd2+. Out of these, how many ions will produce white precipitate with dilute HCl ? 24. What happens when 4–nitrobenzene diazonium chloride reagent reacts with an ammonium salt in the presence of sodium hydroxide solution ? 25. (i) A black coloured compound (B) is formed on passing H2S through the solution of a compound (A) in NH4OH. (ii) (B) on treatment with HCl and potassium chlorate or aquaregia gives (A). (iii) (A) on treatment with KCN gives a buff / reddish-brown coloured precipitate which dissolves in excess of this reagent forming a compound (C). (iv) The compound (C) is changed into a compound (D) when its aqueous solution is boiled in air. (v) The solution of (A) was treated with excess of NaHCO3 & then with bromine water. On cooling & shaking for some time, a green colour of compound (E) is formed. No change is observed on heating. Identify (A) to (E) and give chemical equations.