A 1.0 m solution of HCl in benzene has a freezing point of 0.4 °C. Is HCl an electrolyte in benzene? Explain.

The freezing point may be defined as the point of temperature where liquid start changes into liquid in a given atmospheric pressure.

The electrolyte is defined as the molecule which dissociates into ions in solution form.

Firstly,

\({\bf{Number}}\,{\bf{of}}\,{\bf{moles = }}\frac{{{\bf{Mass}}}}{{{\bf{Molar}}\,{\bf{Mass}}}}\)

Then, find the molality of solution

\(\begin{align}{\bf{Molality = }}\frac{{{\bf{Number}}\,{\bf{of}}\,{\bf{moles}}}}{{{\bf{Mass}}\,{\bf{of}}\,{\bf{Solvent}}\,{\bf{(kg)}}}}\\{\bf{Molality = 1}}{\bf{.0m}}\end{align}\)

\({\bf{\Delta Tfreezing = i \times Kf \times m}}\)

\(\begin{align}{}{\Delta {T_f} = {\bf{ }}{{0.4}^o}C}\\{{K_f}of{\bf{ }}Benzene = {\bf{ }}5}\end{align}\)

\(\begin{align}\Delta Tf &= i \times Kf \times m\\0.4 &= i \times 5 \times 1\\i &= \frac{{0.4}}{5}\\i &= 0.08\end{align}\)

The Van’t Hoff factor is less than 1 for Electrolyte. Hence, HCl is and electrolyte in benzene.