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Question

m/takeAssignment/takeCovalentActivity.do?locator-assignment-take&takeAssignm.; [Refe rences The compound VCl4 undergoes dimerization in solution: When 6.6834 g VCl, is dissolved in 100.0 g carbon tetrachloride, the freezing point is lowered by 6.05°C. Calculate the value of the equilibrium constant for the dimerization of VCl, at this temperature. (The density of the equilibrium mixture is 1.696 g/em2, and Kf 29.8°Ckg/mol for CCl4) Submit Answer Try Another Version 10 item attempts remaining Previous Next

Explanation / Answer

Freezing point depression = kf x molality of the solute

observed molality = 6.05/29.8 = 0.203 molal

Molality of the solute = number of moles in one kg of the solvent

number of moles of solute = mass/molar mass

molar mass of VCl4 is 192.75 g/mol

number of moles of VCl4 = 6.6834/192.75 = 0.03467

0.03467 moles in 100 g solvent

then 0.3467 moles in 1000 g solvent.

Calculated molality = 0.3467 molal

vant Hoff factor = observed molality/calculated molality = 0.203/0.3467 = 0.5855

vant Hoff factor = 1-0.5 x Association constat

Association constant = 0.8289

Number of moles of V2Cl8 = 0.8289 x 0.03467 = 0.02874

number of moles of VCl4 = 0.03467 (1-0.8289) = 0.0059

Equilibrium constant = [V2Cl8]/[VCl4]2 = 0.02874/(0.0059x0.0059)= 816.72

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