akeAssignment/takeCovalentActivity.do?locator assignment-take Use the References

Question

akeAssignment/takeCovalentActivity.do?locator assignment-take Use the References to access important values if needed for this question. The freezing point of ethanol, CH3CH2OH, is-117.300 °C at 1 atmosphere. Kdethanol) = 199 /m f the compound were dissolved in 278.3 grams of ethanol, the solution began to freeze at -117 nonvolatile and a non-electrolyte. .411 °C. The compound was also found to be What is the molecular weight they determined for this compound? g/mol 9 more group attempts remaining

Explanation / Answer

Mass of non-electrolyte solute = 13.81 g

mass of ethanol = 278.3 g = 0.2783 kg

molality of solution = 13.81 g/molar mass of unknown x 0.278.3 kg

dTf = -117.411 - (-117.300) = 0.111 oC

Kf = 1.99 oC/m

i = 1

Using,

dTf = i.Kf.m

0.111 = 1 x 13.81 x 1.99/molar mass of unknown x 0.2783

molar mass of unknown = 889.632 g/mol  

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