Calculate the molar mass of a non-electrolyte that lowers the freezing point of 25.0 g of water to - 3.9 oC when 4.27 g of the substance is dissolved in the water.
See your post above.
To calculate the molar mass of the non-electrolyte, we will use the equation:
ΔTf = Kf × m
Where:
ΔTf = freezing point depression
Kf = freezing point depression constant (for water, it is 1.86 °C/m)
m = molality of the solute (moles of solute per kg of solvent)
First, let's calculate the change in freezing point (ΔTf):
ΔTf = -3.9 °C
Next, we need to calculate the molality of the solute (m):
Mass of solute (molar mass of the solute) = 4.27 g
Mass of solvent (water) = 25.0 g
Molality (m) = moles of solute / kg of solvent
= (mass of solute / molar mass of solute) / (mass of solvent / 1000)
Molality (m) = (4.27 g / molar mass of solute) / (25.0 g / 1000)
Now, let's rearrange the equation to solve for the molar mass of the solute:
molar mass of solute = 4.27 g / (m × 25.0 g / 1000)
However, we don't have the value for molality (m) yet. To find it, we need to know the number of moles of solute and the mass of the solvent (water).
The number of moles of solute can be calculated using the molar mass formula:
moles of solute = mass of solute / molar mass of solute
From the given information, we have the mass of the solute (4.27 g), so we need to find the molar mass of the solute to calculate the moles of solute.
To summarize, in order to calculate the molar mass of the non-electrolyte, we need to find the moles of solute and the molality of the solute. To find the moles of solute, we need the molar mass of the solute. Therefore, we are missing some crucial information to solve the problem.