Answer:
We can use the freezing point depression equation:
ΔTf = Kf * m
where ΔTf is the change in freezing point, Kf is the freezing point depression constant for water (1.86 °C kg/mol), and m is the molality of the solution.
First, we need to calculate the molality of the solution:
molality = moles of solute / mass of solvent (in kg)
We have 1.50 g of NaCl, which is:
moles of NaCl = mass / molar mass = 1.50 g / 58.44 g/mol = 0.02569 mol
The mass of water is given as 0.255 kg. So, the molality of the solution is:
molality = 0.02569 mol / 0.255 kg = 0.1007 mol/kg
Now, we can use the freezing point depression equation to calculate the change in freezing point:
ΔTf = Kf * m = 1.86 °C kg/mol * 0.1007 mol/kg = 0.1873 °C
Finally, we can find the freezing point of the solution by subtracting the change in freezing point from the normal freezing point of water (0 °C):
freezing point = 0 °C - 0.1873 °C = -0.1873 °C
Rounding to one decimal place, the freezing point of the solution is -0.2 °C.