Step1 Let M be molar mass of solute ; Moles of solute =1.2463/M
Step2 ΔTf= 4.9 ; Kf= 9.8 C/m
Step3 Molality of solute =(1.2463/M)(1000/10.9303)
Step4 ΔTf = Kf xMolality ; 9.8x1.2463x1000/Mx 10.9303 =4.9
Step5 M= 228.04
The freezing point of a solution of 1.104 g of an unknown nonelectrolyte dissolved in 36.81 g of benzene is 1.08°C. Pure benzene freezes at 5.48°C and its Kf value is 5.12°C/m. What is the molecular weight of the compound?
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26. The freezing point depression of a solution of 1.45g sample of an unknown nonelectrolyte dissolved in 25.00 mL of benzene(density d=0.879 g/mL) is 1.28°C. Pure benzene has Kf value of 5.12°C/m. What is the molecular weight of the compound? (10 points)
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