At what tempature will a 3.0 m solution of sodium fluride freeze?
To determine the temperature at which a 3.0 m solution of sodium fluoride will freeze, you need to know the freezing point depression constant of the solvent, which is water in this case. The freezing point depression constant for water is approximately 1.86 °C/m.
The freezing point depression is given by the formula:
ΔT = i * Kf * m
Where:
ΔT = freezing point depression
i = van't Hoff factor (number of particles the solute dissociates into)
Kf = freezing point depression constant
m = molality of the solution (moles of solute per kilogram of solvent)
For sodium fluoride (NaF), the van't Hoff factor is 2 because it dissociates into Na+ and F- ions in water.
Given that the molality (m) of the solution is 3.0 m, we can substitute these values into the formula to calculate the freezing point depression:
ΔT = 2 * 1.86 °C/m * 3.0 m
ΔT = 11.16 °C
The freezing point of pure water is 0 °C, so to find the freezing point of the sodium fluoride solution, we need to subtract the freezing point depression from the freezing point of water:
Freezing point of NaF solution = 0 °C - 11.16 °C
Freezing point of NaF solution ≈ -11.16 °C
Therefore, the 3.0 m solution of sodium fluoride will freeze at approximately -11.16 °C.