JEE Mains · Chemistry · STD 12 -1. Solution and colligative properties
Molecules of benzoic acid \((C_6H_5COOH)\) dimerise in benzene. \(‘w’\,g\) of the acid dissolved in \(30\,g\) of benzene shows a depression in freezing point equal to \(2\,K.\) If the percentage association of the acid to form dimer in the solution is \(80,\) then \(w\) is : ............. \(\mathrm{g}\) (Given that \(K_f = 5\,K\, kg\,mol^{-1},\) Molar mass of benzoic acid \(= 122\,g\,mol^{-1}\) )
- A \(2.4\)
- B \(1\)
- C \(1.5\)
- D \(1.8\)
Answer & Solution
Correct Answer
(A) \(2.4\)
Step-by-step Solution
Detailed explanation
\(2A\, \to \,{A_2}\) \(1 - \alpha \) \(\frac{\alpha }{2}\) \(1 - 0.8\) \(\frac{{0.8}}{2}\) \(i\, = 1 - 0.8\, + \,\frac{{0.8}}{2}\, = \,0.6\) \(\Delta {T_f}\, = \,{K_f}\, \times \,\,i\,\, \times \,\,m\)…
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