calculate the freezing point of 0.1m of
a)NaCl (b) glacial acetic acid
delta T = i*kf*molality
i = 1 for acetic acid
i = 2 for NaCl
Substitute for Kf and molality; solve for delta T and subtract from zero C.
To calculate the freezing point of a solution, you need to use the concept of freezing point depression. Freezing point depression is the phenomenon that occurs when a solute is added to a solvent, causing the freezing point of the solvent to decrease.
In order to calculate the freezing point of a solution, you will need to know the molality (m) of the solute, the molal freezing point depression constant (Kf) of the solvent, and the normal freezing point (°C) of the pure solvent.
(a) Calculating the freezing point of 0.1m NaCl solution:
1. Find the molal freezing point depression constant (Kf) of water. For water, the Kf value is 1.86 °C/m.
2. Determine the molality (m) of NaCl. Here, the molality is given as 0.1m.
3. Use the formula ∆T = Kf * m to calculate the freezing point depression (∆T) caused by the NaCl.
∆T = 1.86 °C/m * 0.1m = 0.186 °C
4. Subtract the freezing point depression (∆T) from the normal freezing point of water, which is 0 °C.
Freezing point = 0 °C - 0.186 °C = -0.186 °C
Therefore, the freezing point of a 0.1m NaCl solution is approximately -0.186 °C.
(b) Calculating the freezing point of glacial acetic acid:
Unlike water, glacial acetic acid does not have a well-known and widely available freezing point depression constant. However, assuming that glacial acetic acid behaves similarly to other organic solvents, we can use an approximate value for the Kf of other organic solvents, which is around 1-2 °C/m.
1. Assume a value for the molal freezing point depression constant (Kf) of glacial acetic acid. Let's use 1.5 °C/m as an example.
2. Determine the molality (m) of glacial acetic acid. Let's assume it as 0.1m.
3. Use the formula ∆T = Kf * m to calculate the freezing point depression (∆T) for glacial acetic acid.
∆T = 1.5 °C/m * 0.1m = 0.15 °C
4. Subtract the freezing point depression (∆T) from the normal freezing point of glacial acetic acid. The normal freezing point of glacial acetic acid is approximately 16.6 °C.
Freezing point = 16.6 °C - 0.15 °C = 16.45 °C
Therefore, the freezing point of a 0.1m glacial acetic acid solution is approximately 16.45 °C.