ΔTf=kf×m×i …(i)
Molecular weight of C6H5COOH=112
n = 2 because benzoic acid is dimerised, β = 80 % = 0.8
Here i=(n1−1)β+1
i=(21−1)0.8+1
=0.6
Put the value in equation (i)
2=0.6×100030112wt.of benzoic acid×5
weight of benzoic acid =2.4g
JEE Main 2019 — Chemistry Physical Chemistry
Molecules of benzoic acid (C6H5COOH) dimerise in 30g of benzene. ' w ' g of benzoic acid 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=5Kmol−1, molar mass of benzoic acid =122gmol−1)
Held on 12 Jan 2019 · Verified 6 Jul 2026.
1.0g
2.4g
1.8g
1.5g
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