When 3.695 g of urea was dissolved in 104.8 g of benzene, the freezing point was 275.6 K. What is the formula mass of this compound? The freezing point depression constant for benzene is 5.12 (°C*kg)/mol. The melting point and boiling points are 5.50°C and 80.10°C, respectively.
pleaseeeeeee show me how to do this im so lost
thank you
pleaseeeeeee show me how to do this im so lost
thank you
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Freezing pt depression= kf m
Where kf is the freezing constant, and m is the molality of the solution.
Molality=moles solute/kg solvent
So, you need to calculate moles of urea, and kg of benzene. (Simple conversions, I'm assuming you know how to do those.) except, we don't know molality yet.
So, first convert 275.6 to C, which is 2.6, then subtract 5.5-2.6=2.9
2.9 is the change in freezing point
Now we have 2.9=5.12(molality)
2.9/5.12=molality.
Once you have the molality, you know it equals (x moles of urea/.1048 kg benzene) solve for moles of urea, and then you have g/ mole of urea, which is the formula mass.
Where kf is the freezing constant, and m is the molality of the solution.
Molality=moles solute/kg solvent
So, you need to calculate moles of urea, and kg of benzene. (Simple conversions, I'm assuming you know how to do those.) except, we don't know molality yet.
So, first convert 275.6 to C, which is 2.6, then subtract 5.5-2.6=2.9
2.9 is the change in freezing point
Now we have 2.9=5.12(molality)
2.9/5.12=molality.
Once you have the molality, you know it equals (x moles of urea/.1048 kg benzene) solve for moles of urea, and then you have g/ mole of urea, which is the formula mass.
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