Question

Calculate the mass of ascorbic acid (Vitamin C, C₆H₈O₆₎ to be dissolved in 75 g of acetic acid to lower its melting point by 1.5°C. Kf = 3.9 K kg mol−¹

Answer 1

Mass of acetic acid, w1 = 75 g

Molar mass of ascorbic acid (C₆H8O₆), M2 = 6 × 12 + 8 × 1 + 6 × 16

 = 176 g mol⁻¹

 Lowering of melting point, ∆Tf = 1.5 K

 We know that: 

Hence, 5.08 g of ascorbic acid is needed to be dissolved.

 Note: There is a slight variation in this answer and the one given in the NCERT textbook.