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Molecules of benzoic acid (C6H5COOH) dimerize in benzene. 'w' g of the acid dissolved in 30 g of benzene shows a depression in freezing point equal to 2K. If the percentage association of the acid to form dimer in the solution is 80, then w is  (Given that Kf = 5 K kg mol−1, Molar mass of benzoic acid = 122 g mol−1)

(a)

1.8g

(b)

2.4g

(c)

1.0g

(d)

1.5g


Question ID - 52396 | Toppr Answer

Molecules of benzoic acid (C6H5COOH) dimerize in benzene. 'w' g of the acid dissolved in 30 g of benzene shows a depression in freezing point equal to 2K. If the percentage association of the acid to form dimer in the solution is 80, then w is  (Given that Kf = 5 K kg mol−1, Molar mass of benzoic acid = 122 g mol−1)

(a)

1.8g

(b)

2.4g

(c)

1.0g

(d)

1.5g

1 Answer - 5876 Votes

3537

Answer Key : (b) -

f T = i kf m

2=0.6 × 5 ×

 (i = 1 − 0.8 +0.4 = 0.6)

W=2.44g



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