Qualitative Analysis (Cations) Exercise -2

Qualitative Analysis (Cations)  Marked questions are recommended for Revision. PART - I : ONLY ONE OPTION CORRECT TYPE 1. 2. Which of the following compound does not gives ppt with dil. HCl ? (A) AgNO3 (B) Pb(NO3)2 (C) Hg2(NO3)2 (D) Hg(NO3)2 KI gives precipitate with all the cations given : (A) Ag+, Hg22+, Pb2+ (B) Cu2+, Zn2+, Ni2+ (D) Ag+, Ca2+, Sr2+ (C) Na+, Ca2+, Mg2+ 3. Three test tubes A, B, C cation Pb2+, Hg22+ and Ag+ (but unknown to each, aqueous solution NaOH is added in excess). Following changes occur. A : Black ppt, B : Brown ppt, which disolve in NH3, C : White ppt but dissolves in excess of NaOH A, B and C contain respectively : (A) Pb2+, Hg22+, Ag+ (B) Hg22+, Ag+, Pb2+ + 2+ 2+ (C) Ag , Pb , Hg2 (D) Ag+, Hg22+, Pb2+ 4. dil. HCl → white ppt. Salt mixture ⎯⎯⎯⎯ salt mixture contains cations of : (A) Pb2+ and Hg2+ (B) Pb2+ and Hg22+ 5. (C) Pb2+ and Ag+ (D) None of these (C) Hg(NO3)2 (D) AgNO3 A compound (X) reacts in the following ways. The compound (X) is likely to be (A) Pb(NO3)2 (B) CaCrO4 6. When excess of SnCl2 is added to a solution of HgCl2, a white ppt turning grey is obtained. The grey colour is due to the formation of : (A) Hg2Cl2 (B) SnCl2 (C) Sn (D) Hg 7. An aqueous solution of a substance gives a white ppt. on treatment with dil HCl, which dissolves on heating. When hydrogen sulphide is passed through the hot acidic solution, a black ppt is obtained.The subtance is a: (A) Hg2+ salt (B) Cu2+ salt (C) Ag+ salt (D) Pb2+ salt 8. Three seperate sample of a solution of a single salt gave these results one formed a white precipitate with excess of ammonia solution, one formed a white precipitate with dil. NaCl solution and one formed a black precipitate with H2S. The salt could be : (A) AgNO3 (B) Pb(NO3)2 (C) Hg(NO3)2 (D) MnSO4 9. A pale green crystalline metal salt of M dissolves freely in water. On standing it gives a brown ppt on addition of aqueous NaOH. The metal salt solution also gives a black ppt on bubbling H 2S in basic medium. An aqueous solution of the metal salt decolourizes the pink colour of the permanganate solution. The metal in the metal salt solution is : (A) copper (B) aluminum (C) lead (D) iron 10. K4[Fe(CN)6] can be used to precipitate one or more out of Fe2+, Fe3+, Zn2+, Cu2+, Ca2+ : (A) only Fe2+, Fe3+ (B) only Fe3+,Zn2+,Cu2+ (C) all but not Ca2+ (D) all of these. Qualitative Analysis (Cations) 11. Ferric alum gives deep red colour with NH4SCN due to the formation of : (A) Al(SCN)3 (B) [Fe(SCN)3]– (C) Fe(SCN)3 (D) None of these. 12. Nessler's reagent is used to detect. (A) CrO42– (B) PO43– (C) MnO4– (D) NH4+ 13. On the addition of a solution containing CrO 42– & CH3COOH acid to the solution of Ba2+, Sr2+ and Ca2+ ions, the ppt obtained first will be of : (A) CaCrO4 (B) SrCrO4 (C) BaCrO4 (D) a mixture of all the three 14. A salt on treatment with dil. HCl gives a pungent smelling gas and a yellow precipitate. The salt gives green flame when tested. The solution gives a yellow precipitate with potassium chromate. The salt is : (A) NiSO4 (B) BaS2O3 (C) PbS2O3 (D) CuSO4 15. A chloride dissolves appreciably in cold water. When placed on a platinum wire in Bunsen flame, no distinctive colour is noticed. The cation of chloride is : (A) Mg2+ (B) Ba2+ (C) Pb2+ (D) Ca2+ 16. In fifth group, (NH4)2CO3 is added to precipitate out the carbonates. We do not add Na2CO3 because : (A) CaCO3 is soluble in Na2CO3 (B) Na2CO3 increases the solubility of fifth group carbonates (C) MgCO3 will be precipitated out in fifth group (D) none 17. A metal salt solution forms a yellow precipitate with potassium chromate in acetic acid, a white precipitate with dilute sulphuric acid, but gives no precipitate with sodium chloride or iodide, it is : (A) lead salt (B) silver salt (C) barium salt (D) strontium salt PART - II : SINGLE AND DOUBLE VALUE INTEGER TYPE 1. An aqueous solution contains Hg2+, Hg22+, Pb2+, Ag+, Bi3+ and Cd2+. Out of these, how many ions will produce white precipitate with dilute HCl ? 2. A solution of Hg2+ ion on treatment with a solution of cobalt(II) thiocyanate gives rise to a deep blue crystalline precipitate. Then the coordination number of mercury in the deep blue coloured compound is: 3. The sum of number of p-p bonds present in gas (Y) & (Z) ? 4. 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. 5. In how many of the following reactions, one of the product is obtained as a yellow precipitate : (a) Ba2+ + CrO42– ⎯⎯→ product (b) NH4+ + [PtCl6]2– ⎯⎯→ product (c) NH4+ + [Co(NO2)6]3– ⎯⎯→ product (d) Ca2+ + [Fe(CN)6]4– + K+ ⎯⎯→ product (e) Sr2+ + CO32– ⎯⎯→ product Qualitative Analysis (Cations) 6. Total number of metal nitrates given below, which give the following reaction, (i) AgNO3 (ii) Pb(NO3)2 (iii) Cu(NO3)2 (iv) Cd(NO3)2 (v) Zn(NO3)2 (v) Ni(NO3)2 (vi) Al(NO3)3 Excess NH3.H2O aq. solution of Metal Nitrate No change in colour and no ppt. remains in the test tube 7. Aqueous CuSO4 decolorizes on addition of excess KCN due to formation of complex (A). In complex "A". If (i) Number of d orbitals participating in hybridisation is / are 'a' (ii) Coordination number of Cu is "c". then find 8a + 5c. 8. Co2+ + CN– ⎯⎯→ "A" (reddish brown) ppt. "A" + CN– (excess) ⎯⎯→ "B" (brown solution) "B" + O2 + 2H2O ⎯⎯→ "C" (yellow solution) then find (a + b) for complex "C" if a = coordination number of Co b = charge on complex (consider the magnitude) 9. How many of the following reactions give yellow ppt. (i) NaBr + AgNO3 ⎯→ (ii) (iii) NaBr + Pb(NO3)2 ⎯→ (iv) (v) Na2S + Cd(CH3COO)2 ⎯→ (vi) (vii) K2CrO4 + AgNO3 ⎯→ (viii) NaI + AgNO3 ⎯→ NaI + Pb(NO3)2 ⎯→ K2CrO4 + Pb(CH3COO)2 ⎯→ NaBr + Chlorine water (excess) ⎯→ PART - III : ONE OR MORE THAN ONE OPTIONS CORRECT TYPE 1. Which of the following is/are correctly matched ? (A) BiI3  ⎯⎯→ Black precipitate (B) CuI  ⎯⎯→ White precipitate (C) PbI2  ⎯⎯→ Yellow precipitate 2. 3. (D) HgI2  ⎯⎯→ Red precipitate Which of the following are completely soluble in concentrated ammonia solution? (A) AgCl (B) AgBr (C) Ag2CrO4 (D) Ag boiled → products Hg2I2 (green) ⎯⎯⎯ with H2 O Which of the following statement is / are correct with respect to the products ? (A) Black precipitate of mercury(I) oxide is formed. (B) Violet colour gas is evolved. (C) Red precipitate of HgI2 is formed. (D) Mercury is obtained 4. Which of the following cations form coloured (not white) precipitates with aqueous solution of KI and this precipitate does not dissolve in excess of reagent ? (A) Hg2+ (B) Hg22+ (C) Ag+ (D) Cu2+ 5. Which of the following statements is/are true ? (A) Ag+ ions do not give white precipitate with excess of concentrated HCl. (B) Cu2+ ions produce a white precipitate when KCN solution is added in a small quantity, and allowed to stand. (C) Hg2+ ions give deep blue precipitate with cobalt acetate and ammonium thiocyanate. (D) Black precipitate of BiI3 turns orange when heated with water. Qualitative Analysis (Cations) 6. 7. K solution is the reagent for the analysis of : (A) Hg2+ (B) Pb2+ (C) Ag+ Which of the following metal sulphide are in brown/balck in colour ? (A) HgS (B) PbS (C) Bi2S3 (D) Cu2+ (D) Sb2S3 8. Which of the following cations form(s) black precipitate(s) with H 2S (g) ? (A) Cu2+ (B) Sb3+ (C) Pb2+ (D) Bi3+ 9. Which of the following mixture of cations can be separated by adding excess NH 3 solution ? (A) Zn2+, Mn2+ (B) Zn2+, Cd2+ (C) Zn2+, Pb2+ (D) Zn2+, Cu2+ 10. CoCl2 + KNO2 + CH3COOH ⎯⎯→ [X] + H2O + KCl + CH3COOK + NO (Unbalanced equation) Which is / are correct for 'X'? (A) X is a yellow crystalline solid which is insoluble in water. (B) X is a green coloured compounds known as Rinman's green. (C) IUPAC name of X is potassium hexanitrito –N– cobaltate (II) (D) The compound X is an inner orbital complex. 11. Which of the following is/are correct for potassium ferrocyanide ? (A) It gives a brown precipitate with Cu2+ ions. (B) It gives a white precipitate of mixed salt with Ca2+ ions. (C) It in excess gives a bluish white/white precipitate with Zn 2+. (D) It develops a deep red colouration with Fe 3+. PART - IV : COMPREHENSION Read the following passage carefully and answer the questions. Comprehension # 1 H2 S (g) → Black precipitate ‘B’, soluble in 50% HNO3 forming ‘C’. Aqueous solution of ‘A’ ⎯⎯⎯⎯ White precipitate dissolves in Black precipitate ‘D’ hydrochloric acid but on dilution with water again white turbidity appears 'E'. Moreover, the salt 'A' on heating with solid K2Cr2O7 and concentrated H2SO4 produces deep red vapours which dissolve in sodium hydroxide solution forming a yellow solution. This yellow solution gives yellow precipitate with Ba(NO3)2 solution. On the basis of the aforesaid characteristic informations answer the following questions : 1. Acidified solution of ‘A’, on treatment with KI gives black precipitate 'F' which dissolves in excess of reagent forming the coloured compound 'G'. The chemical composition of 'F' and 'G' are respectively : (A) HgI2 and [HgI4]2– (B) PbI2 and [PbI4]2– (C) BiI3 and [BiI4]– (D) CuI and CuI2. 2. The black precipitate 'F' on heating with water produces : (A) Hg(OH)2 (B) BiOI (C) BiO.OH 3. (D) CuO.OH Select the correct statement. (A) Aqueous solution of 'A' reacts with AgNO3 solution to give white precipitate which turns into yellow on treatment with sodium arsenite. (B) Aqueous solution of 'A' produces white precipitate with sodium hydroxide which turns into yellowishwhite on boiling. (C) White turbidity 'E' is soluble in dilute mineral acids. (D) All of these. Qualitative Analysis (Cations) Comprehension # 2 A student was given a sample of colourless solution containing three cations and was asked to identify the cations. Student carried out a series of reactions as given below. 4. 5. 6. Precipitates ‘A’, ‘B’ and ‘C’ are respectively : (A) Al(OH)3, BaSO4 and AgCl (C) AgCl, Ca(OH)2 and ZnSO4 (B) AgCl, BaSO4 and Zn(OH)2 (D) ZnCl2, BaSO4 and Al(OH)3 White precipitate 'A' is not soluble in : (A) NH3 (B) dilute HCl (C) KCN (D) Na2S2O3 Which of the following statement is correct ? (A) Precipitate 'C' forms Rinmann's green in Co(NO3)2 test. (B) Precipitate 'B' is appreciably soluble in boiling concentrated H 2SO4. (C) Precipitate (A) on exposure to sunlight or ultraviolet radiations turns black. (D) All of these. Comprehension # 3 Answer Q.7, Q.8 and Q.9 by appropriately matching the information given in the three columns of the following table. In Column-1 cation are given while in Column-2 reagent are given which is used for test and in Column-3 observation are given. [Consider each solution to be aqueous unless stated.] Column-1 Column-2 Column-3 (I) Bi3+ (i) NH3 (P) Black / white precipitate is obtained. (II) Cu2+ (ii) KI (Q) Blue / Brown precipitate is obtained. (III) Fe3+ (iii) KCN (R) Form soluble complex in excess reagent. (IV) Zn2+ (iv) K4[Fe(CN)6] (S) Redox reaction take place. 7. 8. 9. The only incorrect combination is: (A) (I) (ii) (P) (B) (II) (ii) (S) (C) (II) (ii) (R) (D) (III) (iii) (R) The only correct combination is: (A) (II) (ii) (R) (B) (III) (ii) (Q) (C) (III) (i) (R) (D) (II) (iii) (S) The only incorrect combination is: (A) (III) (iv) (Q) (B) (IV) (ii) (P) (C) (I) (i) (P) (D) (IV) (i) (R) Qualitative Analysis (Cations) EXERCISE - 2 PART - I 1. (D) 2. (A) 3. (B) 4. (C) 5. (D) 6. (D) 7. (D) 8. (B) 9. (D) 10. (D) 11. (C) 12. (D) 13. (C) 14. (B) 15. (A) 16. (C) 17. (C) 4. 2 PART - II (Hg22+, Pb2+, Ag+) 1. 3 5. 3 (a,b,c) 9. 5 (i), (ii), (iv), (v), (vi) 6. 3 (I, IV, V) 2. 4 3. 4 7. 20 8. a = 6 ; b = 3 (a + b = 9) PART - III 1. (ABCD) 2. (ABC) 3. (CD) 4. (BC) 5. (ABCD) 6. (ABCD) 7. (ABC) 8. (ACD) 9. (AC) 10. (AD) 11. (ABC) 5. (B) PART - IV 1. (C) 2. (B) 3. (D) 4. (B) 6. (D) 7. (C) 8. (D) 9. (B)