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QJEEM24Cha4cf: JEE Main 2024 Chemistry - Class 12 JEEM24Cha4cf Solution: We have three aqueous solutions of labelled as ' ', ' ' and ' ' …

We have three aqueous solutions of NaCl\mathrm{NaCl} labelled as ' A\mathrm{A} ', ' B\mathrm{B} ' and ' C\mathrm{C} ' with concentration 0.1M0.1 \mathrm{M} , 0.01M0.01 \mathrm{M} and 0.001M0.001 \mathrm{M} , respectively. The value of van 't Hoff factor(i) for these solutions will be in the order :

Multiple Choice Options

  • A iA<iC<iB\mathrm{i}_{\mathrm{A}}<\mathrm{i}_{\mathrm{C}}<\mathrm{i}_{\mathrm{B}}
  • B iA<iB<iC\mathrm{i}_{\mathrm{A}}<\mathrm{i}_{\mathrm{B}}<\mathrm{i}_{\mathrm{C}}
  • C iA>iB>iC\mathrm{i}_{\mathrm{A}}>\mathrm{i}_{\mathrm{B}}>\mathrm{i}_{\mathrm{C}}
  • D iA=iB=iC\mathrm{i}_{\mathrm{A}}=\mathrm{i}_{\mathrm{B}}=\mathrm{i}_{\mathrm{C}}

Step-by-Step Verified Solution

Salt Values of i (for different conc. of a Salt)
NaCl 0.1 M 0.01 M 0.001 M
1.87 1.94 1.94

The van 't Hoff factor (i) is used to describe the number of particles a solute formula unit produces in a solution. For an electrolyte like NaCl\mathrm{NaCl} , which dissociates completely in very dilute solutions, the theoretical value of ii is approximately 2, since NaCl\mathrm{NaCl} dissociates into Na+\mathrm{Na}^+ and Cl−\mathrm{Cl}^- ions.

In real scenarios, as the concentration of the solution decreases (making the solution more dilute), the interaction between the ions decreases, allowing more complete dissociation. Therefore, for practical purposes, the van 't Hoff factor ii approaches its theoretical maximum value as concentration decreases. Thus, for NaCl\mathrm{NaCl} solutions of concentrations 0.1M0.1 \mathrm{M} , 0.01M0.01 \mathrm{M} , and 0.001M0.001 \mathrm{M} , the fact that NaCl\mathrm{NaCl} dissociates more completely in more dilute solutions implies that ii increases with decreasing concentration.

Hence, the order of ii based on the concentration would be \mathrm{i}_{\mathrm{A}} &lt; \mathrm{i}_{\mathrm{B}} &lt; \mathrm{i}_{\mathrm{C}} , as concentration 0.1 \mathrm{M} &gt; 0.01 \mathrm{M} &gt; 0.001 \mathrm{M} , respectively. Thus, option B correctly describes the order of the van 't Hoff factors for these solutions.

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