Q) At 20 degrees C the vapor pressure of benzene (C6H6) is 75 torr and that of t
ID: 1075608 • Letter: Q
Question
Q) At 20 degrees C the vapor pressure of benzene (C6H6) is 75 torr and that of toluene (C7H8) is 22 torr. Assume that benzene and toluene form an ideal solution. A) What is the composition in mole fractions of a solution that has vapor pressure of 45 tore at 20 degrees C?-XC6H6: -CC7H8:
B) What is the mole fraction of benzene in the vapor above the solution described in part a?
Q) Calculate the mass of ethylene glycol (C2H6O2) that must be added to 1.00 kg of ethanol (C2H5OH) to reduce its vapor pressure by 12.5 torr at 35 degrees C. The vapor pressure of pure ethanol at 35 degrees C is 1.00x 10^2 torr. Q) At 20 degrees C the vapor pressure of benzene (C6H6) is 75 torr and that of toluene (C7H8) is 22 torr. Assume that benzene and toluene form an ideal solution. A) What is the composition in mole fractions of a solution that has vapor pressure of 45 tore at 20 degrees C?
-XC6H6: -CC7H8:
B) What is the mole fraction of benzene in the vapor above the solution described in part a?
Q) Calculate the mass of ethylene glycol (C2H6O2) that must be added to 1.00 kg of ethanol (C2H5OH) to reduce its vapor pressure by 12.5 torr at 35 degrees C. The vapor pressure of pure ethanol at 35 degrees C is 1.00x 10^2 torr. A) What is the composition in mole fractions of a solution that has vapor pressure of 45 tore at 20 degrees C?
-XC6H6: -CC7H8:
B) What is the mole fraction of benzene in the vapor above the solution described in part a?
Q) Calculate the mass of ethylene glycol (C2H6O2) that must be added to 1.00 kg of ethanol (C2H5OH) to reduce its vapor pressure by 12.5 torr at 35 degrees C. The vapor pressure of pure ethanol at 35 degrees C is 1.00x 10^2 torr.
Explanation / Answer
(a) What is the composition in mole fractions of a solution that has a vapor pressure of 40. torr at 20°C?
Let X be the mole fraction of benzene in this ideal solution. Thus 1-X is the mole fraction of toluene in this ideal solution.
The following is given:
75X + 22(1-X) = 45, or:
53X = 23, and X = 23/53.
Benzene's mole fraction is 23/53, and toluene's mole fraction is 30/53.
(b) What is the mole fraction of benzene in the vapor above the solution described in part (a)?
(75*23/53)/45 = 72.32%
2)
1.00 x 10^2 - 12.5=87.5 torr
87.5 = 1.00 x 10^2 X
X = mole fraction ethanol=0.875 = 21.7 / 21.7 + moles C2H6O2
19.3 + 0.875 moles C2H6O2 = 21.7
moles C2H6O2 = 2.74
mass C2H6O2 = 2.74 x 62.07 g/mol=170.07 g
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