What is the boiling point (in degrees Celsius ) of each of the solutions below? For water, Kb = 0.51 (Degrees C * kg)/mol The vapor pressure of water at 45.0C is 71.93 mm Hg.
1. A solution of 15.0g of urea, CH4N2O, in 164 g of water at 45.0 degrees C.
For this one, I've gone 100 + ((.25*1000)/(9.11)) and got 127.44 degrees C..
However, this is incorrect. What am I doing wrong?
2. A solution of 12.0g of LiCl in 164 g of water at 45.0C, assuming complete dissociation.
I've tried something similar but once again with incorrect results.
Any suggestions on what I am doing wrong/need to do?
To find the boiling point elevation of a solution, you need to use the equation:
ΔTb = Kb * m
where ΔTb is the boiling point elevation, Kb is the molal boiling point elevation constant, and m is the molality of the solution (moles of solute per kilogram of solvent).
Let's go through each solution step by step.
1. A solution of 15.0g of urea, CH4N2O, in 164 g of water at 45.0 degrees C.
First, calculate the molality (m) of the solution. Since the molecular weight of urea is 60.06 g/mol, we first need to convert the mass of urea and water into moles:
moles of urea = mass of urea / molar mass of urea
moles of water = mass of water / molar mass of water
Next, calculate the molality:
m = moles of urea / mass of water (in kg)
Now, you can substitute the values into the equation:
ΔTb = Kb * m
Given that the molal boiling point elevation constant (Kb) for water is 0.51 (Degrees C * kg)/mol, you can calculate the boiling point elevation.
2. A solution of 12.0g of LiCl in 164 g of water at 45.0C, assuming complete dissociation.
First, calculate the number of moles of LiCl:
moles of LiCl = mass of LiCl / molar mass of LiCl
Next, calculate the molality:
m = moles of LiCl / mass of water (in kg)
Now, you can substitute the values into the equation:
ΔTb = Kb * m
Again, given that the molal boiling point elevation constant (Kb) for water is 0.51 (Degrees C * kg)/mol, you can calculate the boiling point elevation.
Make sure to double-check your calculations and units to avoid any errors.