Let’s use the K_b and K_f chart and the above formulae to solve the following problems.

What will be the freezing point and boiling point of a solution containing 3.8 gms of benzoic acid in 50 gms of chloroform ?

Freezing point depression

D T_f = 0.623 ´ 4.68 = 2.915

So, the freezing point of chloroform solution

- 63.5 - 2.91 = - 66.415⁰C

D T_b = 0.623 ´ 3.63 = 2.261

So, the boiling point of chloroform solution

61.2 + 2.261 = 63.46⁰C

What will be the molecular weight of the solute if a solution prepared from 500 gms of a solute in 3 kg of water has a boiling point elevation f 2⁰C than that of pure water ?

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Index

Chapter 9