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Page 1 JEE Solved Example on Liquid State JEE Mains Q1: Mole fraction of A vapours above the solution in mixture of ?? and ?? ( ?? ?? = ?? . ?? ) will be [Given: ?? ?? ?? = ?????? ???????? and ?? ?? ° = ?????? ???????? ] (A) 0.4 (B) 0.8 (C) 0.25 (D) None of these Ans: (C) We have, ?? - ?? ?? + ?? ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 0.4 × 100+ 0.6 × 200 = 40 + 120 = 160 mmHg ?? ?? = 40mmHg ?? ?? = ?? . ?? ?? ?? ?? - 40 160 - 0.25 Q2: The exact mathematical expression of Raoult's law is (A) ?? ° -?? ?? ?? ° (B) ?? ° -?? ?? ?? ° = ?? ?? (C) ?? ° -?? ?? ?? ?? = ?? ?? (D) ?? ° -?? ?? ?? ° = ?? × ?? Ans: (C) Raoult's Law = ?? 0 -?? ?? 0 = ?? ?? +?? ?? + ?? ?? = ?? 0 ?? 0 - ?? 1 + ?? ?? = ?? 0 ?? 0 - ?? ?? ?? = ?? 0 - ?? 0 + ?? ?? 0 - ?? ? ?? 0 - ?? ?? = ?? ?? Sol 3: (A)P- ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 1 1 + 3 · 100+ 3 1 + 3 · 80 = 25 + 60 = 85 mmHg Page 2 JEE Solved Example on Liquid State JEE Mains Q1: Mole fraction of A vapours above the solution in mixture of ?? and ?? ( ?? ?? = ?? . ?? ) will be [Given: ?? ?? ?? = ?????? ???????? and ?? ?? ° = ?????? ???????? ] (A) 0.4 (B) 0.8 (C) 0.25 (D) None of these Ans: (C) We have, ?? - ?? ?? + ?? ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 0.4 × 100+ 0.6 × 200 = 40 + 120 = 160 mmHg ?? ?? = 40mmHg ?? ?? = ?? . ?? ?? ?? ?? - 40 160 - 0.25 Q2: The exact mathematical expression of Raoult's law is (A) ?? ° -?? ?? ?? ° (B) ?? ° -?? ?? ?? ° = ?? ?? (C) ?? ° -?? ?? ?? ?? = ?? ?? (D) ?? ° -?? ?? ?? ° = ?? × ?? Ans: (C) Raoult's Law = ?? 0 -?? ?? 0 = ?? ?? +?? ?? + ?? ?? = ?? 0 ?? 0 - ?? 1 + ?? ?? = ?? 0 ?? 0 - ?? ?? ?? = ?? 0 - ?? 0 + ?? ?? 0 - ?? ? ?? 0 - ?? ?? = ?? ?? Sol 3: (A)P- ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 1 1 + 3 · 100+ 3 1 + 3 · 80 = 25 + 60 = 85 mmHg Q3: A mixture contains 1 mole of volatile liquid ?? ( ?? ?? ° = ?????? ???????? ) and 3 moles of volatile liquid ?? ( ?? ?? ?? = ???? ???????? ). If solution behaves ideally, the total pressure of the distillate is (A) ???? ???????? (B) ???? . ???? ?????? (C) ???? ???????? (D) ???? ???????? Ans: (A) ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 Q4: Assuming each salt to be ???? % dissociated, which of the following will have highest boiling point? (A) Decimolar ???? ?? ( ???? ?? ) ?? (B) Decimolar ???????? ?? (C) Decimolar ???? ?? ???? ?? (D) A solution obtained by mixing equal volumes of (B) and (C) Ans: (A) ?T b = ikm ?? ?? will be highest for solute for which ??? ?? is highest or i is highest. For same degree of dissociation, i ?? n, n is largest for Al 2 ( SO 4 ) 3 ( n = 5) Q5: The vapour pressure of a solvent decreased by ???? ???? of ???? when a non-volatile solute was added to the solvent. The mole fraction of solute in solution is 0.2 , what would be mole fraction of the solvent if decrease in vapour pressure is ???? ???? of ???? . (A) 0.2 (B) 0.4 (C) 0.6 (D) 0.8 Ans: (C) ?? 0 -?? ?? 0 = ?? ?? ??? ?? 0 = ?? ?? ??? 1 ??? 2 = ?? ?? 1 ?? ?? 2 10 20 = 0.2 ?? ?? 2 ? ?? ?? 2 = 0.4 ? ?? ?? = 1 - 0.4 = 0.6 Page 3 JEE Solved Example on Liquid State JEE Mains Q1: Mole fraction of A vapours above the solution in mixture of ?? and ?? ( ?? ?? = ?? . ?? ) will be [Given: ?? ?? ?? = ?????? ???????? and ?? ?? ° = ?????? ???????? ] (A) 0.4 (B) 0.8 (C) 0.25 (D) None of these Ans: (C) We have, ?? - ?? ?? + ?? ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 0.4 × 100+ 0.6 × 200 = 40 + 120 = 160 mmHg ?? ?? = 40mmHg ?? ?? = ?? . ?? ?? ?? ?? - 40 160 - 0.25 Q2: The exact mathematical expression of Raoult's law is (A) ?? ° -?? ?? ?? ° (B) ?? ° -?? ?? ?? ° = ?? ?? (C) ?? ° -?? ?? ?? ?? = ?? ?? (D) ?? ° -?? ?? ?? ° = ?? × ?? Ans: (C) Raoult's Law = ?? 0 -?? ?? 0 = ?? ?? +?? ?? + ?? ?? = ?? 0 ?? 0 - ?? 1 + ?? ?? = ?? 0 ?? 0 - ?? ?? ?? = ?? 0 - ?? 0 + ?? ?? 0 - ?? ? ?? 0 - ?? ?? = ?? ?? Sol 3: (A)P- ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 1 1 + 3 · 100+ 3 1 + 3 · 80 = 25 + 60 = 85 mmHg Q3: A mixture contains 1 mole of volatile liquid ?? ( ?? ?? ° = ?????? ???????? ) and 3 moles of volatile liquid ?? ( ?? ?? ?? = ???? ???????? ). If solution behaves ideally, the total pressure of the distillate is (A) ???? ???????? (B) ???? . ???? ?????? (C) ???? ???????? (D) ???? ???????? Ans: (A) ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 Q4: Assuming each salt to be ???? % dissociated, which of the following will have highest boiling point? (A) Decimolar ???? ?? ( ???? ?? ) ?? (B) Decimolar ???????? ?? (C) Decimolar ???? ?? ???? ?? (D) A solution obtained by mixing equal volumes of (B) and (C) Ans: (A) ?T b = ikm ?? ?? will be highest for solute for which ??? ?? is highest or i is highest. For same degree of dissociation, i ?? n, n is largest for Al 2 ( SO 4 ) 3 ( n = 5) Q5: The vapour pressure of a solvent decreased by ???? ???? of ???? when a non-volatile solute was added to the solvent. The mole fraction of solute in solution is 0.2 , what would be mole fraction of the solvent if decrease in vapour pressure is ???? ???? of ???? . (A) 0.2 (B) 0.4 (C) 0.6 (D) 0.8 Ans: (C) ?? 0 -?? ?? 0 = ?? ?? ??? ?? 0 = ?? ?? ??? 1 ??? 2 = ?? ?? 1 ?? ?? 2 10 20 = 0.2 ?? ?? 2 ? ?? ?? 2 = 0.4 ? ?? ?? = 1 - 0.4 = 0.6 Q6: Elevation of boiling point of 1 molar aqueous glucose solution (density = ?? . ?? ?? /???? ) is (A) ?? ?? (B) ?? . ???? ?? ?? (C) ?? . ???? ?? ?? (D) ?? . ???? ?? ?? Ans: (D) For every 1 L solution, moles of glucose = 1, weight of so ?? = 1.2 × 1000 = 1.2 kg Weight of glucose = 180 g Weight of solvent = 1200- 180 = 1020 g ? molality - 1 1.02 - 0.98 m ? ??? ?? = ?? ?? ?? = 0.98 K b Q7: What will be the molecular weight of ???????? ?? determined in its aq. solution experimentally from depression of freezing point? (A) 111 (B) < ?????? (C) > ?????? (D) Data insufficient Sol 7: (B) i = Normal molecular wt Observed molecular wt > 1 ? Observed molecular wt < normal molecular wt. Q8 1.0 molal aqueous solution of an electrolyte ?? ?? ?? ?? is ???? % ionized. The boiling point of the solution at ?? ?????? is ?? ?? ( ?? ?? ?? ) = ?? . ???? ?? ???? ?????? ?? (A) ?????? . ???? ?? (B) ?????? ?? (C) ?????? . ?? ?? (D) ?????? . ???? ?? Ans: ( ?? ) ?? 2 ?? 3 ? 2?? + + 3?? - ?? = 0.6 ?? = 5 i - 1 + ( n - 1) ?? = 3.4 ??? ?? = iK b m = 3.4 × 0.52 × 1 = 1.768 K T b = 373 + 1.768 = 374.768 K Page 4 JEE Solved Example on Liquid State JEE Mains Q1: Mole fraction of A vapours above the solution in mixture of ?? and ?? ( ?? ?? = ?? . ?? ) will be [Given: ?? ?? ?? = ?????? ???????? and ?? ?? ° = ?????? ???????? ] (A) 0.4 (B) 0.8 (C) 0.25 (D) None of these Ans: (C) We have, ?? - ?? ?? + ?? ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 0.4 × 100+ 0.6 × 200 = 40 + 120 = 160 mmHg ?? ?? = 40mmHg ?? ?? = ?? . ?? ?? ?? ?? - 40 160 - 0.25 Q2: The exact mathematical expression of Raoult's law is (A) ?? ° -?? ?? ?? ° (B) ?? ° -?? ?? ?? ° = ?? ?? (C) ?? ° -?? ?? ?? ?? = ?? ?? (D) ?? ° -?? ?? ?? ° = ?? × ?? Ans: (C) Raoult's Law = ?? 0 -?? ?? 0 = ?? ?? +?? ?? + ?? ?? = ?? 0 ?? 0 - ?? 1 + ?? ?? = ?? 0 ?? 0 - ?? ?? ?? = ?? 0 - ?? 0 + ?? ?? 0 - ?? ? ?? 0 - ?? ?? = ?? ?? Sol 3: (A)P- ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 1 1 + 3 · 100+ 3 1 + 3 · 80 = 25 + 60 = 85 mmHg Q3: A mixture contains 1 mole of volatile liquid ?? ( ?? ?? ° = ?????? ???????? ) and 3 moles of volatile liquid ?? ( ?? ?? ?? = ???? ???????? ). If solution behaves ideally, the total pressure of the distillate is (A) ???? ???????? (B) ???? . ???? ?????? (C) ???? ???????? (D) ???? ???????? Ans: (A) ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 Q4: Assuming each salt to be ???? % dissociated, which of the following will have highest boiling point? (A) Decimolar ???? ?? ( ???? ?? ) ?? (B) Decimolar ???????? ?? (C) Decimolar ???? ?? ???? ?? (D) A solution obtained by mixing equal volumes of (B) and (C) Ans: (A) ?T b = ikm ?? ?? will be highest for solute for which ??? ?? is highest or i is highest. For same degree of dissociation, i ?? n, n is largest for Al 2 ( SO 4 ) 3 ( n = 5) Q5: The vapour pressure of a solvent decreased by ???? ???? of ???? when a non-volatile solute was added to the solvent. The mole fraction of solute in solution is 0.2 , what would be mole fraction of the solvent if decrease in vapour pressure is ???? ???? of ???? . (A) 0.2 (B) 0.4 (C) 0.6 (D) 0.8 Ans: (C) ?? 0 -?? ?? 0 = ?? ?? ??? ?? 0 = ?? ?? ??? 1 ??? 2 = ?? ?? 1 ?? ?? 2 10 20 = 0.2 ?? ?? 2 ? ?? ?? 2 = 0.4 ? ?? ?? = 1 - 0.4 = 0.6 Q6: Elevation of boiling point of 1 molar aqueous glucose solution (density = ?? . ?? ?? /???? ) is (A) ?? ?? (B) ?? . ???? ?? ?? (C) ?? . ???? ?? ?? (D) ?? . ???? ?? ?? Ans: (D) For every 1 L solution, moles of glucose = 1, weight of so ?? = 1.2 × 1000 = 1.2 kg Weight of glucose = 180 g Weight of solvent = 1200- 180 = 1020 g ? molality - 1 1.02 - 0.98 m ? ??? ?? = ?? ?? ?? = 0.98 K b Q7: What will be the molecular weight of ???????? ?? determined in its aq. solution experimentally from depression of freezing point? (A) 111 (B) < ?????? (C) > ?????? (D) Data insufficient Sol 7: (B) i = Normal molecular wt Observed molecular wt > 1 ? Observed molecular wt < normal molecular wt. Q8 1.0 molal aqueous solution of an electrolyte ?? ?? ?? ?? is ???? % ionized. The boiling point of the solution at ?? ?????? is ?? ?? ( ?? ?? ?? ) = ?? . ???? ?? ???? ?????? ?? (A) ?????? . ???? ?? (B) ?????? ?? (C) ?????? . ?? ?? (D) ?????? . ???? ?? Ans: ( ?? ) ?? 2 ?? 3 ? 2?? + + 3?? - ?? = 0.6 ?? = 5 i - 1 + ( n - 1) ?? = 3.4 ??? ?? = iK b m = 3.4 × 0.52 × 1 = 1.768 K T b = 373 + 1.768 = 374.768 K Q9: The van't Hoff factor for a dilute aqueous solution of glucose is (A) Zero (B) 1.0 (C) 1.5 (D) 2.0 Ans: (B) Since, glucose does not dissociate, ?? - 0 ? ?? - 1 Q10: The correct relationship between the boiling points of very dilute solution of ???????? ?? ( ?? ?? ?? ) and ???????? ?? ( ?? ?? ?? ) having the same molar concentration is (A) ?? ?? = ?? ?? (B) ?? ?? > ?? ?? (C) ?? ?? < ?? ?? (D) ?? ?? = ?? ?? Ans: (B) ??? ?? = ?? ?? ?? ?? For ?? equimolar solution are equimolal also very dilute. ? ??? ?? ? i i AlCl 3 > i CaCl 2 (as i ?? n, ?? NCl 3 = 4, n CaCl 2 = 2 ) ?T b AlCl 3 > ?T b CaCl 2 T 1 > T 2 Q11: A 0.001 molal solution of a complex [MA] in water has the freezing point of -?? . ???????? ° ?? . Assuming ?????? % ionization of the complex salt and ?? ?? for ?? ?? ?? = ?? . ???? ???? -?? , what the correct representation for the complex (A) [???? ?? ] (B) [???? ?? ]?? (C) [???? ?? ]?? ?? (D) [???? ?? ]?? ?? Ans: (C) ??? ?? = ?? ?? ?? ?? i - ??? 1 ?? 1 ?? = 0.0054 1.86 × 0.001 = 2.903 ?? - 1 ? 1 + ( ?? - 1) ?? - 2.9 ˜ 3 ?? - 1 = 2 ?? = 3 ? Out of the given options, only ( C ) is possible Page 5 JEE Solved Example on Liquid State JEE Mains Q1: Mole fraction of A vapours above the solution in mixture of ?? and ?? ( ?? ?? = ?? . ?? ) will be [Given: ?? ?? ?? = ?????? ???????? and ?? ?? ° = ?????? ???????? ] (A) 0.4 (B) 0.8 (C) 0.25 (D) None of these Ans: (C) We have, ?? - ?? ?? + ?? ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 0.4 × 100+ 0.6 × 200 = 40 + 120 = 160 mmHg ?? ?? = 40mmHg ?? ?? = ?? . ?? ?? ?? ?? - 40 160 - 0.25 Q2: The exact mathematical expression of Raoult's law is (A) ?? ° -?? ?? ?? ° (B) ?? ° -?? ?? ?? ° = ?? ?? (C) ?? ° -?? ?? ?? ?? = ?? ?? (D) ?? ° -?? ?? ?? ° = ?? × ?? Ans: (C) Raoult's Law = ?? 0 -?? ?? 0 = ?? ?? +?? ?? + ?? ?? = ?? 0 ?? 0 - ?? 1 + ?? ?? = ?? 0 ?? 0 - ?? ?? ?? = ?? 0 - ?? 0 + ?? ?? 0 - ?? ? ?? 0 - ?? ?? = ?? ?? Sol 3: (A)P- ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 = 1 1 + 3 · 100+ 3 1 + 3 · 80 = 25 + 60 = 85 mmHg Q3: A mixture contains 1 mole of volatile liquid ?? ( ?? ?? ° = ?????? ???????? ) and 3 moles of volatile liquid ?? ( ?? ?? ?? = ???? ???????? ). If solution behaves ideally, the total pressure of the distillate is (A) ???? ???????? (B) ???? . ???? ?????? (C) ???? ???????? (D) ???? ???????? Ans: (A) ?? - ?? ?? ?? ?? 0 + ?? ?? ?? ?? 0 Q4: Assuming each salt to be ???? % dissociated, which of the following will have highest boiling point? (A) Decimolar ???? ?? ( ???? ?? ) ?? (B) Decimolar ???????? ?? (C) Decimolar ???? ?? ???? ?? (D) A solution obtained by mixing equal volumes of (B) and (C) Ans: (A) ?T b = ikm ?? ?? will be highest for solute for which ??? ?? is highest or i is highest. For same degree of dissociation, i ?? n, n is largest for Al 2 ( SO 4 ) 3 ( n = 5) Q5: The vapour pressure of a solvent decreased by ???? ???? of ???? when a non-volatile solute was added to the solvent. The mole fraction of solute in solution is 0.2 , what would be mole fraction of the solvent if decrease in vapour pressure is ???? ???? of ???? . (A) 0.2 (B) 0.4 (C) 0.6 (D) 0.8 Ans: (C) ?? 0 -?? ?? 0 = ?? ?? ??? ?? 0 = ?? ?? ??? 1 ??? 2 = ?? ?? 1 ?? ?? 2 10 20 = 0.2 ?? ?? 2 ? ?? ?? 2 = 0.4 ? ?? ?? = 1 - 0.4 = 0.6 Q6: Elevation of boiling point of 1 molar aqueous glucose solution (density = ?? . ?? ?? /???? ) is (A) ?? ?? (B) ?? . ???? ?? ?? (C) ?? . ???? ?? ?? (D) ?? . ???? ?? ?? Ans: (D) For every 1 L solution, moles of glucose = 1, weight of so ?? = 1.2 × 1000 = 1.2 kg Weight of glucose = 180 g Weight of solvent = 1200- 180 = 1020 g ? molality - 1 1.02 - 0.98 m ? ??? ?? = ?? ?? ?? = 0.98 K b Q7: What will be the molecular weight of ???????? ?? determined in its aq. solution experimentally from depression of freezing point? (A) 111 (B) < ?????? (C) > ?????? (D) Data insufficient Sol 7: (B) i = Normal molecular wt Observed molecular wt > 1 ? Observed molecular wt < normal molecular wt. Q8 1.0 molal aqueous solution of an electrolyte ?? ?? ?? ?? is ???? % ionized. The boiling point of the solution at ?? ?????? is ?? ?? ( ?? ?? ?? ) = ?? . ???? ?? ???? ?????? ?? (A) ?????? . ???? ?? (B) ?????? ?? (C) ?????? . ?? ?? (D) ?????? . ???? ?? Ans: ( ?? ) ?? 2 ?? 3 ? 2?? + + 3?? - ?? = 0.6 ?? = 5 i - 1 + ( n - 1) ?? = 3.4 ??? ?? = iK b m = 3.4 × 0.52 × 1 = 1.768 K T b = 373 + 1.768 = 374.768 K Q9: The van't Hoff factor for a dilute aqueous solution of glucose is (A) Zero (B) 1.0 (C) 1.5 (D) 2.0 Ans: (B) Since, glucose does not dissociate, ?? - 0 ? ?? - 1 Q10: The correct relationship between the boiling points of very dilute solution of ???????? ?? ( ?? ?? ?? ) and ???????? ?? ( ?? ?? ?? ) having the same molar concentration is (A) ?? ?? = ?? ?? (B) ?? ?? > ?? ?? (C) ?? ?? < ?? ?? (D) ?? ?? = ?? ?? Ans: (B) ??? ?? = ?? ?? ?? ?? For ?? equimolar solution are equimolal also very dilute. ? ??? ?? ? i i AlCl 3 > i CaCl 2 (as i ?? n, ?? NCl 3 = 4, n CaCl 2 = 2 ) ?T b AlCl 3 > ?T b CaCl 2 T 1 > T 2 Q11: A 0.001 molal solution of a complex [MA] in water has the freezing point of -?? . ???????? ° ?? . Assuming ?????? % ionization of the complex salt and ?? ?? for ?? ?? ?? = ?? . ???? ???? -?? , what the correct representation for the complex (A) [???? ?? ] (B) [???? ?? ]?? (C) [???? ?? ]?? ?? (D) [???? ?? ]?? ?? Ans: (C) ??? ?? = ?? ?? ?? ?? i - ??? 1 ?? 1 ?? = 0.0054 1.86 × 0.001 = 2.903 ?? - 1 ? 1 + ( ?? - 1) ?? - 2.9 ˜ 3 ?? - 1 = 2 ?? = 3 ? Out of the given options, only ( C ) is possible Q12: The vapour pressure of a solution of a non -volatile electrolyte ?? in a solvent ?? is ???? % of the vapour pressure of the solvent at the same temperature. If the molecular weight of the solvent is 0.3 times the molecular weight of solute, the weight ratio of the solvent and solute are (A) 0.15 (B) 5.7 (C) 0.2 (D) 4.0 Sol 12: (B) We have ?? = 0.95?? 0 ?? 0 - ?? ?? 0 - ?? ?? - 0.05 ?? ?? ?? ?? - 0.05 ?? ?? ?? ?? + ?? ?? ?? ?? ?? ?? ?? ?? - 1 20 ?? ?? ?? ?? + 1 20 ?? ?? ?? ?? 19 20 ?? ?? ?? ?? - 1 20 ?? ?? ?? ?? ?? ?? ?? ?? - 19. ?? ?? ?? ?? 19 × 0.3 - 5.7 Q13: The vapour pressure of a saturated solution of sparingly soluble salt ( ?????? ?? ) was ???? . ???? ???????? at ???? ° ?? . If the vapour pressure of pure ?? ?? ?? is ???? . ???? ???????? at ?????? ?? , what is the solubility of sparingly soluble salt ?????? ?? in mole/litre (A) ?? . ???? × ???? ?? (B) ?? . ???? × ???? ?? (C) ?? . ???? × ???? ?? (D) ?? . ???? × ???? ?? Ans: (A) XCl 3 ? X + 3Cl ?? - 4 ?? - 1 ?? = 1 + 3 = 5 ?? ?? - ?? 0 - ?? ?? 0 ?? ?? = 17.25 - 17.2 17.25 × 4 ?? ?? = 7.24 × 10 -4 = ?? ?? + ?? For n + N - 1, n - 7.24 × 10 -4 ?? = 0.999Read More
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