QJEEM21Ch630f: JEE Main 2021 Chemistry - Class 12 JEEM21Ch630f Solution: C 6 H 6 freezes at 5.5 C. The temperature at which a solution…

Question

Verified Solution • 2025–26 Session moderate

C₆H₆ freezes at 5.5

^\circ

C. The temperature at which a solution of 10g of C₄H₁₀ in 200g of C₆H₆ freeze is __________

^\circ

C. (The molal freezing point depression constant of C₆H₆ is 5.12

^\circ

C/m.)

Accepted Answer

Pure solvent : C₆H₆(l)

Given,

T_f^o = 5.5^\circ C

{K_f} = 5.12^\circ C/m \Rightarrow m = 200g

{m_{solute}} = 10g

Molar mass of solute

{C_4}{H_{10}} = 12 \times 4 + 10 = 58

Solute (C₄H₁₀) is non-dissociative;

\therefore

i = 1

\therefore

\Delta {T_f} = i{K_f}\,m

\Rightarrow (T_f^o - T_f^1) = 1 \times 5.12 \times {{(10/58)} \over {(200/1000)}}

5.5 - T_f^1 = {{5.12 \times 5 \times 10} \over {58}} \Rightarrow T_f^1 = 1.086^\circ C

or

T_f^1 \approx 1^\circ C

Step-by-Step Verified Solution