The mole fraction of NaCl in a solution containing 1 mole of NaCl in 1000 g of water is -  

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  1. 0.0177 
  2. 0.001 
  3. 0.5 
  4. 0.244

Answer (Detailed Solution Below)

Option 1 : 0.0177 
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Detailed Solution

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Explanation:-

  • Mole fraction is defined as the major concentration of a solute and solvent in terms of the number of moles.
  • Mole fraction of a solute(XA) = n  /n A + n B 
  • Mole fraction of a solute(XB) = n B  /n A + n B 

Calculation:- 

⇒ No. of moles = Given mass / Molar mass

⇒ Mole fraction of NaCl = No. of moles in NaCl / Total no. of moles in the solution

⇒ No. of moles of NaCl =  1

⇒ No. of moles of H2O = Given the mass of H2O / Molar mass of H2

⇒ No. of moles of H2O = 1000 / 18 = 55.55

Mole fraction of NaCl = No. of moles in NaCl / No. of moles in NaCl + No. of moles of H2

⇒ Mole fraction of NaCl =  1 / 1 + 55.5 

⇒ Mole fraction of NaCl = 0.0177 

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