A sample of water is found to contain 5.85 % ( w w ) of A B (molecular mass 58.5 ) and 9.50 % ( w w ) X Y₂ (molecular mass 95). Assuming 80 % ionisation of A B and 60 % ionisation of X₂ , the freezing point of water sample is [Given, K_f fo

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A sample of water is found to contain 5.85 % ( w w ) of A B (molecular mass 58.5 ) and 9.50 % ( w w ) X Y₂ (molecular mass 95). Assuming 80 % ionisation of A B and 60 % ionisation of X₂ , the freezing point of water sample is [Given, K_f for water 1.86 ~K ~kg ~mol ⁻¹ , Freezing point of pure water is 273 ~K and A , B and Y are monovalent ions.]

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Correct answer: A. 264.25 ~K

A B X Y₂5.85 %9.5 % array rlrl m & = 5.85 58.5 1000 84.65 m & = 9.5 95 1000 84.65 & =1.181 & & =1.181 array =0.8 (for 80 % ionisation) =0.6 (for 60 % ionisation) array rlrl i & =1+(2-1) 0.8 & i & =1+(3-1) 0.6 & =1.8 & & =2.2 array Now, T_f=K_f [i₁ m₁+i₂ m₂ ] aligned & =1.86[1.8(1.181)+2.2(1.181)] & =1.86[4.72]=8.78 aligned

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