what is the freezing point of 16.7g of LiCl in 136g of water, assuming complete dissociation for water kf= -1.86/mol
To determine the freezing point of the solution, you need to use the equation:
ΔT = Kf * m
Where:
ΔT = The change in temperature (in this case, the freezing point depression)
Kf = The molal freezing point depression constant (provided as -1.86 °C/m)
m = The molality of the solute particles in the solution
To find the molality (m), you need to calculate the moles of solute (LiCl) and the mass of the solvent (water).
1. Calculate the moles of LiCl:
To do this, divide the mass of LiCl by its molar mass.
The molar mass of LiCl can be found using the periodic table:
Molar mass of Li = 6.94 g/mol
Molar mass of Cl = 35.45 g/mol
Add the molar masses together to get the molar mass of LiCl.
2. Calculate the molality (m):
Divide the moles of LiCl by the mass of the water.
3. Calculate the freezing point depression (ΔT):
Multiply the molality by the freezing point depression constant (Kf).
4. Determine the freezing point:
Subtract the freezing point depression from the normal freezing point of pure water, which is 0 °C.
Now, let's calculate the freezing point depression for the given values.
Given:
Mass of LiCl = 16.7 g
Mass of water = 136 g
Kf = -1.86 °C/m
1. Calculate the moles of LiCl:
Molar mass of LiCl = (6.94 + 35.45) g/mol
Moles of LiCl = Mass of LiCl / Molar mass of LiCl
2. Calculate the molality (m):
Molality (m) = Moles of LiCl / Mass of water (in kg)
3. Calculate the freezing point depression (ΔT):
ΔT = Kf * m
4. Determine the freezing point:
Freezing point = 0 °C - ΔT
Plug in the values into the equations and calculate step by step to find the freezing point depression and the freezing point of the solution.