How do you find the molecular formula from freezing point depression?
The equation that describes the relationship between freezing point depression and molality is:
- DTf = (Kf)(m)
- Tf° is the freezing point of the pure solvent.
- Tf is the freezing point of the solution.
- Kf is the molal freezing point depression constant.
- m is the molality of the solution.
How do you find the molecular weight from the freezing point?
Step 1: Calculate the freezing point depression of the solution. Step 2 : Calculate the molal concentration of the solution using the freezing point depression. Step 3: Calculate the molecular weight of the unknown using the molal concentration.
How does freezing point depression affect molar mass?
Thus, as the molar mass increases, the freezing point depression decreases. That is, increasing the molar (or molecular) mass will have a smaller effect on the freezing point.
How do you find the freezing point on a graph?
freezing point of the solution is determined from the graph by drawing two straight lines through the data points above and below the freezing point. The temperature corresponding to the intersection of the two lines is the freezing point of the solution.
Why is freezing point depression a Colligative property?
The freezing point depression thus is called a colligative property. The explanation for the freezing point depression is then simply that as solvent molecules leave the liquid and join the solid, they leave behind a smaller volume of liquid in which the solute particles can roam.
What are the units of KF?
Kf is the molal freezing point depression constant of the solvent (1.86 °C/m for water). m = molality = moles of solute per kilogram of solvent. i = the number of dissolved particles (Van’t Hoff Factor).
Which type of property depression in freezing point is?
colligative property
Of a solvent and a nonvolatile solute The freezing point depression thus is called a colligative property. The explanation for the freezing point depression is then simply that as solvent molecules leave the liquid and join the solid, they leave behind a smaller volume of liquid in which the solute particles can roam.
How does molar mass affect the freezing point?
Thus, as the molar mass increases, the freezing point depression decreases . That is, increasing the molar (or molecular) mass will have a smaller effect on the freezing point.
How to calculate freezing point depression?
Calculate the molality of the NaCl molality (m) of NaCl = moles of NaCl/kg water From the periodic table, find the atomic masses of the elements: atomic mass Determine the van ‘t Hoff factor The van ‘t Hoff factor, i, is a constant associated with the amount of dissociation of the solute in the solvent. Find ΔT
Why is depression in freezing point?
The freezing point depression thus is called a colligative property. The explanation for the freezing point depression is then simply that as solvent molecules leave the liquid and join the solid, they leave behind a smaller volume of liquid in which the solute particles can roam.
What is the molal freezing point depression constant?
The proportionality constant ,, is called the molal freezing-point depression constant. It is a constant that is equal to the change in the freezing point for a 1-molal solution of a nonvolatile molecular solute. For water, the value of is -1.86°C/ m.
