Question

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

Answer 1

Answer :

• Mass of ascorbic acid = 5.077 g.

Step-by-step explanation:

Given that,

• Mass of solvent (acetic acid), $\rm{w_1}$ = 75 g.
• Lowering in melting point, $\rm{\Delta\:T_f}$ = 1.5°C.
• For acetic acid, $\rm{K_f=3.9\:K\:kg\:mol^{-1}}$

Also,

• Molar mass of solvent (acetic acid), $\rm{M_1}$ = 60 g/mol.
• Molar mass of solute (ascorbic acid), $\rm{M_2}$ = 176 g/mol.

$\hrulefill$

$\rm{We\:know,\:M_2=\dfrac{1000\times{}K_f\times{}w_2}{w_1\times{}\Delta\:T_f}}$

$\bold{OR}$

$\rm{w_2=\dfrac{M_2\times{}w_1\times{}\Delta\:T_f}{1000\times{}K_f}}$

$\rm{w_2=\dfrac{(176\:g\:mol^{-1})(75\:g)(1.5\:K)}{(1000\:g\:kg^{-1})(3.9\:K\:kg\:mol^{-1})}}$

$\rm{w_2=}\bold{5.077\:g}$