i need to know if I am in the right tract please let me know...I am calulating the molality of the following exercise so I could be able to apply the formula T=Kf * molality
calculate the freezing point of a solution containin 12.2 grams of benzoic acid, dissolved in 250 grams of nitrobenzene. The freezing point of nitrobenzene is 5.7 C, and its freezing point depression constant is 7.O C/m
M= # mols/#kg solvent
so,
C6H5CO2H
C= 12.011 * 6 = 72.066
H= 1.00794
c= 12.011
O= 15.9994
H= 1.000794
amu= 102.09
12.2 g * 1mol/102.09g =0.120 mol
M= 0.120 mol/0.250Kg= 0.48
am I correct please help me
I didnt' check the math on the molmass, so double check that , but you have it down right procedure.
thansk
from the texbook K(f)= 5.12 C/m but from the exercise is 7.0 C/m which one should i use to solve fro the freezing point? please help
if so then the solution will be
Delta T= Kf * M
T= 7.0 C/m * O.474mol/g
T=3.32 C
The freezing point of the solution will be
5.7 C - 3.32 C = 2.38 C please let me know if this is correct? please
I didn't check math, but it exactly the right way to work it. The symbol for molality is m, and for molarity M. The units for molality are moles/kg
oh i see m ok thanks
To determine if you have calculated the molality correctly, let's go through the steps together:
1. Calculate the number of moles of benzoic acid (C6H5CO2H) by dividing its mass by its molar mass:
12.2 g / 122.09 g/mol = 0.100 mol
2. Calculate the molality (M) by dividing the number of moles of solute by the mass of the solvent in kilograms:
M = 0.100 mol / 0.250 kg = 0.40 mol/kg
So, it seems you made a mistake in your calculation. The correct molality is 0.40 mol/kg, not 0.48 mol/kg.
Now, let's proceed to calculate the freezing point depression using the formula:
ΔT = Kf * molality
Given that the freezing point depression constant (Kf) is 7.0 °C/m, and the molality (M) is 0.40 mol/kg, we can substitute these values into the formula:
ΔT = 7.0 °C/m * 0.40 mol/kg
ΔT = 2.8 °C
To find the freezing point of the solution, subtract the freezing point depression (ΔT) from the freezing point of the solvent:
Freezing point = 5.7 °C - 2.8 °C
Freezing point = 2.9 °C
Therefore, the freezing point of the solution is calculated to be 2.9 °C.
It's important to double-check your calculations and pay attention to units to ensure accuracy.