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Page 1 JEE Solved Example on Ionic Equilibrium JEE Mains Q1: The conjugate acid of ???? ?? - is (A) ???? ?? (B) ???? ?? ???? (C) ???? ?? + (D) ?? ?? ?? ?? Ans: (A) The conjugate acid has one proton (H + ) more. Hence, for NH 2 - the conjugate acid would be NH 3 (the positive charge of H + and the negative charge of NH 2 - cancel each other out). Q2: Out of the following, amphiprotic species are I. ?????? ?? ?? - II. ???? - III. ?? ?? ???? ?? - IV. ?????? ?? - (A) I, III, IV (B) I and III (C) III and IV (D) All Ans: (C) H 2 PO 4 - And HCO 3 - are amphoteric in nature. HCl+ H 2 PO 4 - ? H 3 PO 4 + Cl -1 NaOH+ H 2 PO 4 - ? HPO 4 -2 + H 2 O Q?? : ???? of an aqueous solution of ???????? at ???? ° ?? should be (A) 7 (B) > ?? (C) < ?? (D) 0 Ans: (C) Halides and alkaline metals dissociate and do not affect the H + as the cation does not alter the H + and the anion does not attract the H + from water. This is why NaCl is a neutral salt. But pH of water decreases as the temperature increases. So option C is correct Page 2 JEE Solved Example on Ionic Equilibrium JEE Mains Q1: The conjugate acid of ???? ?? - is (A) ???? ?? (B) ???? ?? ???? (C) ???? ?? + (D) ?? ?? ?? ?? Ans: (A) The conjugate acid has one proton (H + ) more. Hence, for NH 2 - the conjugate acid would be NH 3 (the positive charge of H + and the negative charge of NH 2 - cancel each other out). Q2: Out of the following, amphiprotic species are I. ?????? ?? ?? - II. ???? - III. ?? ?? ???? ?? - IV. ?????? ?? - (A) I, III, IV (B) I and III (C) III and IV (D) All Ans: (C) H 2 PO 4 - And HCO 3 - are amphoteric in nature. HCl+ H 2 PO 4 - ? H 3 PO 4 + Cl -1 NaOH+ H 2 PO 4 - ? HPO 4 -2 + H 2 O Q?? : ???? of an aqueous solution of ???????? at ???? ° ?? should be (A) 7 (B) > ?? (C) < ?? (D) 0 Ans: (C) Halides and alkaline metals dissociate and do not affect the H + as the cation does not alter the H + and the anion does not attract the H + from water. This is why NaCl is a neutral salt. But pH of water decreases as the temperature increases. So option C is correct Q4: 1 cc of ?? . ?? ???????? is added to 99 cc solution of ???????? . The ???? of the resulting solution will be (A) 7 (B) 3 (C) 4 (D) 1 Ans: (C) No' moles HCl = (1×0.1) 1000 = 10 -4 Volume = 1dm 3 Concentration = moles / volume = 10 -4 1 = 10 -4 This gives a pH of 4 so option (C) is correct. Q5: ???????? of ?? ?????? ?? ?? ???? ?? is mixed with ???????? of ?? ?????? ?? ?? ???? ?? . The ???? of the resulting solution is (A) 1 (B) 2 (C) 2.3 (D) None of these Ans: (B) We have 50 mL of M 200 H 2 SO 4 M 200 = 0.005M solution H 2 SO 4 ? 2H + + SO 4 2- Then [H + ] = 2 × 0.005M= 0.01M pH = -log [H + ] pH = -log 0.01M pH = 2.00 Q6: If ???? ?? for fluoride ion at ???? ° ?? is 10.83 , the ionisation constant of hydrofluoric acid in water at this temperature is: (A) ?? . ???? × ???? -?? (B) ?? . ???? × ???? -?? (C) ?? . ???? × ???? -?? (D) ?? . ???? × ???? -?? Ans: (C) The equation for the dissociation of HF is as follow: HF + H 2 O ? H 3 O + + F - Here pK b = 10.83 ? -log K b = 10.83 Hence, K b = 1.48 × 10 -11 Thus lonization constant of acid K a = K W /K b Page 3 JEE Solved Example on Ionic Equilibrium JEE Mains Q1: The conjugate acid of ???? ?? - is (A) ???? ?? (B) ???? ?? ???? (C) ???? ?? + (D) ?? ?? ?? ?? Ans: (A) The conjugate acid has one proton (H + ) more. Hence, for NH 2 - the conjugate acid would be NH 3 (the positive charge of H + and the negative charge of NH 2 - cancel each other out). Q2: Out of the following, amphiprotic species are I. ?????? ?? ?? - II. ???? - III. ?? ?? ???? ?? - IV. ?????? ?? - (A) I, III, IV (B) I and III (C) III and IV (D) All Ans: (C) H 2 PO 4 - And HCO 3 - are amphoteric in nature. HCl+ H 2 PO 4 - ? H 3 PO 4 + Cl -1 NaOH+ H 2 PO 4 - ? HPO 4 -2 + H 2 O Q?? : ???? of an aqueous solution of ???????? at ???? ° ?? should be (A) 7 (B) > ?? (C) < ?? (D) 0 Ans: (C) Halides and alkaline metals dissociate and do not affect the H + as the cation does not alter the H + and the anion does not attract the H + from water. This is why NaCl is a neutral salt. But pH of water decreases as the temperature increases. So option C is correct Q4: 1 cc of ?? . ?? ???????? is added to 99 cc solution of ???????? . The ???? of the resulting solution will be (A) 7 (B) 3 (C) 4 (D) 1 Ans: (C) No' moles HCl = (1×0.1) 1000 = 10 -4 Volume = 1dm 3 Concentration = moles / volume = 10 -4 1 = 10 -4 This gives a pH of 4 so option (C) is correct. Q5: ???????? of ?? ?????? ?? ?? ???? ?? is mixed with ???????? of ?? ?????? ?? ?? ???? ?? . The ???? of the resulting solution is (A) 1 (B) 2 (C) 2.3 (D) None of these Ans: (B) We have 50 mL of M 200 H 2 SO 4 M 200 = 0.005M solution H 2 SO 4 ? 2H + + SO 4 2- Then [H + ] = 2 × 0.005M= 0.01M pH = -log [H + ] pH = -log 0.01M pH = 2.00 Q6: If ???? ?? for fluoride ion at ???? ° ?? is 10.83 , the ionisation constant of hydrofluoric acid in water at this temperature is: (A) ?? . ???? × ???? -?? (B) ?? . ???? × ???? -?? (C) ?? . ???? × ???? -?? (D) ?? . ???? × ???? -?? Ans: (C) The equation for the dissociation of HF is as follow: HF + H 2 O ? H 3 O + + F - Here pK b = 10.83 ? -log K b = 10.83 Hence, K b = 1.48 × 10 -11 Thus lonization constant of acid K a = K W /K b ?? ?? = 10 -14 ?? ?? = 10 -14 /1.48 × 10 -11 ?? ?? = 6.76 × 10 -4 Thus Ionization constant of HF is 6.76 × 10 -4 Q7: The ???? of an aqueous solution of ?? . ???? solution of a weak monoprotic acid which is ?? % ionised is (A) 1 (B) 2 (C) 3 (D) 11 Ans: (C) [?? ?? ?? + ] = ?? ?? = ?? . ?? × ?? ?????? = ?? × ???? -?? pH = -log [H 3 O + ] = -log 10 -3 = 3 Q8: If ?? ?? and ?? ?? be first and second ionization constant of ?? ?? ???? ?? and ?? ?? >> ?? ?? which is incorrect. (A) [?? + ] = [?? ?? ???? ?? - ] (B) [?? + ] = ?? ?? [?? ?? ???? ?? ] (C) ?? ?? = [?????? ?? - ] (D) [?? + ] = ?? [???? ?? ?? - ] Ans: (D) H 3 PO 4 = H + + H 2 PO 4 - … … … . K 1 H 2 PO 4 - = H + + HPO 4 2- … … … . . K 2 HPO 4 2- = H + + PO 4 3- … … … … . K 3 K 3 = [HPO 4 2- ] H + = [PO 4 3- ] Q9: Which of the following solution will have ???? close to 1.0 ? (A) ?????????? of ?? /???????????? + ?????????? of ?? /???? (B) ???????? of ?? /?????????? + ???????? of ?? /???????????? (C) ???????? of ?? /?????????? + ???????? of ?? /???????????? (D) ???????? of ?? /???????? + ???????? of ?? /?????????? Ans: (D) Molarity of both acid and base is same. Amount of acid used is thrice the amount of base. Thus the pH of the solution will be highly acidic, Page 4 JEE Solved Example on Ionic Equilibrium JEE Mains Q1: The conjugate acid of ???? ?? - is (A) ???? ?? (B) ???? ?? ???? (C) ???? ?? + (D) ?? ?? ?? ?? Ans: (A) The conjugate acid has one proton (H + ) more. Hence, for NH 2 - the conjugate acid would be NH 3 (the positive charge of H + and the negative charge of NH 2 - cancel each other out). Q2: Out of the following, amphiprotic species are I. ?????? ?? ?? - II. ???? - III. ?? ?? ???? ?? - IV. ?????? ?? - (A) I, III, IV (B) I and III (C) III and IV (D) All Ans: (C) H 2 PO 4 - And HCO 3 - are amphoteric in nature. HCl+ H 2 PO 4 - ? H 3 PO 4 + Cl -1 NaOH+ H 2 PO 4 - ? HPO 4 -2 + H 2 O Q?? : ???? of an aqueous solution of ???????? at ???? ° ?? should be (A) 7 (B) > ?? (C) < ?? (D) 0 Ans: (C) Halides and alkaline metals dissociate and do not affect the H + as the cation does not alter the H + and the anion does not attract the H + from water. This is why NaCl is a neutral salt. But pH of water decreases as the temperature increases. So option C is correct Q4: 1 cc of ?? . ?? ???????? is added to 99 cc solution of ???????? . The ???? of the resulting solution will be (A) 7 (B) 3 (C) 4 (D) 1 Ans: (C) No' moles HCl = (1×0.1) 1000 = 10 -4 Volume = 1dm 3 Concentration = moles / volume = 10 -4 1 = 10 -4 This gives a pH of 4 so option (C) is correct. Q5: ???????? of ?? ?????? ?? ?? ???? ?? is mixed with ???????? of ?? ?????? ?? ?? ???? ?? . The ???? of the resulting solution is (A) 1 (B) 2 (C) 2.3 (D) None of these Ans: (B) We have 50 mL of M 200 H 2 SO 4 M 200 = 0.005M solution H 2 SO 4 ? 2H + + SO 4 2- Then [H + ] = 2 × 0.005M= 0.01M pH = -log [H + ] pH = -log 0.01M pH = 2.00 Q6: If ???? ?? for fluoride ion at ???? ° ?? is 10.83 , the ionisation constant of hydrofluoric acid in water at this temperature is: (A) ?? . ???? × ???? -?? (B) ?? . ???? × ???? -?? (C) ?? . ???? × ???? -?? (D) ?? . ???? × ???? -?? Ans: (C) The equation for the dissociation of HF is as follow: HF + H 2 O ? H 3 O + + F - Here pK b = 10.83 ? -log K b = 10.83 Hence, K b = 1.48 × 10 -11 Thus lonization constant of acid K a = K W /K b ?? ?? = 10 -14 ?? ?? = 10 -14 /1.48 × 10 -11 ?? ?? = 6.76 × 10 -4 Thus Ionization constant of HF is 6.76 × 10 -4 Q7: The ???? of an aqueous solution of ?? . ???? solution of a weak monoprotic acid which is ?? % ionised is (A) 1 (B) 2 (C) 3 (D) 11 Ans: (C) [?? ?? ?? + ] = ?? ?? = ?? . ?? × ?? ?????? = ?? × ???? -?? pH = -log [H 3 O + ] = -log 10 -3 = 3 Q8: If ?? ?? and ?? ?? be first and second ionization constant of ?? ?? ???? ?? and ?? ?? >> ?? ?? which is incorrect. (A) [?? + ] = [?? ?? ???? ?? - ] (B) [?? + ] = ?? ?? [?? ?? ???? ?? ] (C) ?? ?? = [?????? ?? - ] (D) [?? + ] = ?? [???? ?? ?? - ] Ans: (D) H 3 PO 4 = H + + H 2 PO 4 - … … … . K 1 H 2 PO 4 - = H + + HPO 4 2- … … … . . K 2 HPO 4 2- = H + + PO 4 3- … … … … . K 3 K 3 = [HPO 4 2- ] H + = [PO 4 3- ] Q9: Which of the following solution will have ???? close to 1.0 ? (A) ?????????? of ?? /???????????? + ?????????? of ?? /???? (B) ???????? of ?? /?????????? + ???????? of ?? /???????????? (C) ???????? of ?? /?????????? + ???????? of ?? /???????????? (D) ???????? of ?? /???????? + ???????? of ?? /?????????? Ans: (D) Molarity of both acid and base is same. Amount of acid used is thrice the amount of base. Thus the pH of the solution will be highly acidic, Q10: What is the percentage hydrolysis of ???????? in ?? /???? solution when the dissociation constant for ?????? is ?? . ?? × ???? -?? and ?? ?? = ?? . ?? × ???? -???? (A) 2.48 (B) 5.26 (C) 8.2 (D) 9.6 Ans: (A) Since NaCN is the salt of a weak acid (HCN) and strong base (NaOH ), the degree of hydrolysis, ?? = v ?? ?? ?? ?? × ?? = 1.0 × 10 -14 × 80 1.3 × 10 -9 = v6.16 × 10 -4 = 2.48 × 10 -2 ? Percentage hydrolysis of NaCN in N/80 Solution is 2.48 Q11: The compound whose ?? . ???? solution is basic is (A) Ammonium acetate (B) Ammonium chloride (C) Ammonium sulphate (D) Sodium acetate Ans: (D) Sodium acetate undergoes anionic hydrolysis CH 3 COO - + H 2 O ? CH 3 COOH+ OH - Q. 12 The ˜ ???? of the neutralisation point of ?? . ?? ?? ammonium hydroxide with ?? . ?? ???????? is (A) 1 (B) 6 (C) 7 (D) 9 Ans: (B) NH 4 OH+ HCl ? NH 4 Cl NH 4 Cl Is a salt of weak base and strong acid .so it give s acidic solution with pH > 7 Q13: If equilibrium constant of ???? ?? ???????? + ?? ?? ?? ? ???? ?? ?????? - + ?? ?? ?? + Is ?? . ?? × ???? -?? , equilibrium constant for ???? ?? ???????? + ???? - ???? ?? ?????? - + ?? ?? ?? is (A) ?? . ?? × ???? -?? (B) ?? . ?? × ???? -?? Page 5 JEE Solved Example on Ionic Equilibrium JEE Mains Q1: The conjugate acid of ???? ?? - is (A) ???? ?? (B) ???? ?? ???? (C) ???? ?? + (D) ?? ?? ?? ?? Ans: (A) The conjugate acid has one proton (H + ) more. Hence, for NH 2 - the conjugate acid would be NH 3 (the positive charge of H + and the negative charge of NH 2 - cancel each other out). Q2: Out of the following, amphiprotic species are I. ?????? ?? ?? - II. ???? - III. ?? ?? ???? ?? - IV. ?????? ?? - (A) I, III, IV (B) I and III (C) III and IV (D) All Ans: (C) H 2 PO 4 - And HCO 3 - are amphoteric in nature. HCl+ H 2 PO 4 - ? H 3 PO 4 + Cl -1 NaOH+ H 2 PO 4 - ? HPO 4 -2 + H 2 O Q?? : ???? of an aqueous solution of ???????? at ???? ° ?? should be (A) 7 (B) > ?? (C) < ?? (D) 0 Ans: (C) Halides and alkaline metals dissociate and do not affect the H + as the cation does not alter the H + and the anion does not attract the H + from water. This is why NaCl is a neutral salt. But pH of water decreases as the temperature increases. So option C is correct Q4: 1 cc of ?? . ?? ???????? is added to 99 cc solution of ???????? . The ???? of the resulting solution will be (A) 7 (B) 3 (C) 4 (D) 1 Ans: (C) No' moles HCl = (1×0.1) 1000 = 10 -4 Volume = 1dm 3 Concentration = moles / volume = 10 -4 1 = 10 -4 This gives a pH of 4 so option (C) is correct. Q5: ???????? of ?? ?????? ?? ?? ???? ?? is mixed with ???????? of ?? ?????? ?? ?? ???? ?? . The ???? of the resulting solution is (A) 1 (B) 2 (C) 2.3 (D) None of these Ans: (B) We have 50 mL of M 200 H 2 SO 4 M 200 = 0.005M solution H 2 SO 4 ? 2H + + SO 4 2- Then [H + ] = 2 × 0.005M= 0.01M pH = -log [H + ] pH = -log 0.01M pH = 2.00 Q6: If ???? ?? for fluoride ion at ???? ° ?? is 10.83 , the ionisation constant of hydrofluoric acid in water at this temperature is: (A) ?? . ???? × ???? -?? (B) ?? . ???? × ???? -?? (C) ?? . ???? × ???? -?? (D) ?? . ???? × ???? -?? Ans: (C) The equation for the dissociation of HF is as follow: HF + H 2 O ? H 3 O + + F - Here pK b = 10.83 ? -log K b = 10.83 Hence, K b = 1.48 × 10 -11 Thus lonization constant of acid K a = K W /K b ?? ?? = 10 -14 ?? ?? = 10 -14 /1.48 × 10 -11 ?? ?? = 6.76 × 10 -4 Thus Ionization constant of HF is 6.76 × 10 -4 Q7: The ???? of an aqueous solution of ?? . ???? solution of a weak monoprotic acid which is ?? % ionised is (A) 1 (B) 2 (C) 3 (D) 11 Ans: (C) [?? ?? ?? + ] = ?? ?? = ?? . ?? × ?? ?????? = ?? × ???? -?? pH = -log [H 3 O + ] = -log 10 -3 = 3 Q8: If ?? ?? and ?? ?? be first and second ionization constant of ?? ?? ???? ?? and ?? ?? >> ?? ?? which is incorrect. (A) [?? + ] = [?? ?? ???? ?? - ] (B) [?? + ] = ?? ?? [?? ?? ???? ?? ] (C) ?? ?? = [?????? ?? - ] (D) [?? + ] = ?? [???? ?? ?? - ] Ans: (D) H 3 PO 4 = H + + H 2 PO 4 - … … … . K 1 H 2 PO 4 - = H + + HPO 4 2- … … … . . K 2 HPO 4 2- = H + + PO 4 3- … … … … . K 3 K 3 = [HPO 4 2- ] H + = [PO 4 3- ] Q9: Which of the following solution will have ???? close to 1.0 ? (A) ?????????? of ?? /???????????? + ?????????? of ?? /???? (B) ???????? of ?? /?????????? + ???????? of ?? /???????????? (C) ???????? of ?? /?????????? + ???????? of ?? /???????????? (D) ???????? of ?? /???????? + ???????? of ?? /?????????? Ans: (D) Molarity of both acid and base is same. Amount of acid used is thrice the amount of base. Thus the pH of the solution will be highly acidic, Q10: What is the percentage hydrolysis of ???????? in ?? /???? solution when the dissociation constant for ?????? is ?? . ?? × ???? -?? and ?? ?? = ?? . ?? × ???? -???? (A) 2.48 (B) 5.26 (C) 8.2 (D) 9.6 Ans: (A) Since NaCN is the salt of a weak acid (HCN) and strong base (NaOH ), the degree of hydrolysis, ?? = v ?? ?? ?? ?? × ?? = 1.0 × 10 -14 × 80 1.3 × 10 -9 = v6.16 × 10 -4 = 2.48 × 10 -2 ? Percentage hydrolysis of NaCN in N/80 Solution is 2.48 Q11: The compound whose ?? . ???? solution is basic is (A) Ammonium acetate (B) Ammonium chloride (C) Ammonium sulphate (D) Sodium acetate Ans: (D) Sodium acetate undergoes anionic hydrolysis CH 3 COO - + H 2 O ? CH 3 COOH+ OH - Q. 12 The ˜ ???? of the neutralisation point of ?? . ?? ?? ammonium hydroxide with ?? . ?? ???????? is (A) 1 (B) 6 (C) 7 (D) 9 Ans: (B) NH 4 OH+ HCl ? NH 4 Cl NH 4 Cl Is a salt of weak base and strong acid .so it give s acidic solution with pH > 7 Q13: If equilibrium constant of ???? ?? ???????? + ?? ?? ?? ? ???? ?? ?????? - + ?? ?? ?? + Is ?? . ?? × ???? -?? , equilibrium constant for ???? ?? ???????? + ???? - ???? ?? ?????? - + ?? ?? ?? is (A) ?? . ?? × ???? -?? (B) ?? . ?? × ???? -?? (C) ?? . ???? × -???? -?? (D) ?? . ???? × ???? ???? Ans: (B) The pH of the solution at the equivalence point will be greater than 7 due to salt hydrolysis. So an indicator giving colour on the basic side will be suitable. Q14: The ???? ?? of a weak acid, ???? , is 4. 80. The ???? ?? of a weak base, ?????? , is 4. 78. The ???? of an aqueous solution of the corresponding salt, BA, will be: (A) 8.58 (B) 4.79 (C) 7.01 (D) 9.22 Ans: (C) It is a salt of weak acid and weak base. [?? + ] = v ?? ?? × ?? ?? ?? ?? On solving we get pH = 7.01 Q15: The range of most suitable indicator which should be used for titration of ?? - ???? + (?? . ???? , ???????? ) with 0.1 ???????? should be (Given: ?? ?? (?? - ) = ???? -?? ) (A) ?? - ?? (B) 3-5 (C) 6-8 (D) ?? - ???? Ans: (B) CH 3 COONa+ HCl ? CH 3 COOH+ NaCl It is an example of titration of weak base with strong acid. Observed pH range for the end point is 3.00 to 6.00 . Q16: The solubility of ?? ?? ?? ?? is ?? mol dm-3. Its solubility product is (A) ?? ?? ?? (B) ???? ?? ?? (C) ???? ?? ?? (D) ?????? ?? ?? Ans: (D) A 2 X 3 ? 2 A +3 + 3X -2 2y 3y Ksp= [A +3 ] 2 [ B -2 ] 3 = (2y) 2 (3y) 3 = 108y 5Read More
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