Question

calculate the freezing point of 1.50 gnaclgnacl in 0.255 kgkg of water. express your answer in degrees celsius to one decimal place.

Answer 1

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.