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.)
Answer (integer)
1
Solution
Pure solvent : C<sub>6</sub>H<sub>6</sub>(l)<br/><br/>Given, <br/><br/>$T_f^o = 5.5^\circ C$<br/><br/>${K_f} = 5.12^\circ C/m \Rightarrow m = 200g$<br/><br/>${m_{solute}} = 10g$<br/><br/>Molar mass of solute ${C_4}{H_{10}} = 12 \times 4 + 10 = 58$<br/><br/>Solute (C<sub>4</sub>H<sub>10</sub>) is non-dissociative;<br/><br/>$\therefore$ i = 1<br/><br/>$\therefore$ $\Delta {T_f} = i{K_f}\,m$<br/><br/>$$ \Rightarrow (T_f^o - T_f^1) = 1 \times 5.12 \times {{(10/58)} \over {(200/1000)}}$$<br/><br/>$$5.5 - T_f^1 = {{5.12 \times 5 \times 10} \over {58}} \Rightarrow T_f^1 = 1.086^\circ C$$<br/><br/>or $T_f^1 \approx 1^\circ C$
About this question
Subject: Chemistry · Chapter: States of Matter · Topic: Gas Laws
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