Bromobenzene, C6H5Br, and chlorobenzene, C6H5Cl, form essentially ideal solutions in all proportions. At 100°C, the equilibrium vapour pressure of bromobenzene is 137mmHg and that of chlorobenzene is 285mmHg. Calculate the equilibrium vapour pressure above a 17.6% (w/w) solution of bromobenzene in chlorobenzene at a temperature of 100°C
16305 mmHg
163 mmHg
25895 mmHg
265 mmHg
157 mmHg
Are you sure the 25895 choice is not 258.95?
Since the solution is 17.6% in bromobenene, that means 17.6 g/100 g soln OR
17.6 g bromobenzene in a solution made up of 17.6 g bromogenzene and (100-17.6 = 82.4 g chlorobenzene).
Determine moles bromo and moles chloro.
Calculate mole fraction bromo and chloro.
Then vapor pressure of each component is
P = X*Po
You will have one partial pressure for the bromo and one partial pressure for th chlor. Add them for the total pressure. Post your work if you get stuck.
i have 0.112 mol of bromo,
and 0.732 mol chloro,
but i am stuck on the mole fraction.
Do i just do 1-0.112= 0.888 or am i missing a step?
ok, this is what I have.
Xbromo= 0.112/+0.732+0.112=0.133
Xchloro= 1-0.133= 0.867
P=Xbromo*p= 0.133*137= 18.221mmHg
P=Xchloro*p= 0.867*285= 247.095mmHg
so I add 18.221+247.095= 265.316mmHg
Is that right?
correct
To calculate the equilibrium vapor pressure above a solution of bromobenzene and chlorobenzene, you can use Raoult's law, an approximation that assumes ideal behavior of solute and solvent.
According to Raoult's law, the vapor pressure of a component in an ideal solution is proportional to its mole fraction in the solution. The mole fraction of bromobenzene can be calculated using its weight fraction.
Given:
Weight fraction of bromobenzene (C6H5Br) = 17.6% (w/w)
Equilibrium vapor pressure of bromobenzene (C6H5Br) = 137 mmHg
Equilibrium vapor pressure of chlorobenzene (C6H5Cl) = 285 mmHg
Step 1: Calculate the mole fraction of bromobenzene (C6H5Br):
Mole fraction of bromobenzene (C6H5Br) = (Weight of C6H5Br) / (Weight of C6H5Br + Weight of C6H5Cl)
Assuming we have 100g of the solution, the weight of C6H5Br = 17.6g
The weight of C6H5Cl can be calculated as 100g - 17.6g = 82.4g
Mole fraction of C6H5Br = 17.6g / (17.6g + 82.4g) = 0.175
Step 2: Calculate the equilibrium vapor pressure above the solution using Raoult's law:
Equilibrium vapor pressure of the solution = (Mole fraction of C6H5Br) * (Vapor pressure of C6H5Br) + (Mole fraction of C6H5Cl) * (Vapor pressure of C6H5Cl)
Equilibrium vapor pressure of the solution = (0.175) * (137 mmHg) + (1 - 0.175) * (285 mmHg)
Calculating this, we get:
Equilibrium vapor pressure of the solution = 23.975 mmHg + 234.725 mmHg = 258.7 mmHg
Therefore, the equilibrium vapor pressure above a 17.6% (w/w) solution of bromobenzene in chlorobenzene at a temperature of 100°C is approximately 258 mmHg.