1. n- butanol has the chemical formula C4H9OH. Since n- butanol has a larger mol
ID: 1007469 • Letter: 1
Question
1. n- butanol has the chemical formula C4H9OH. Since n- butanol has a larger molar mass than ethanol, n-butanol:
a. will experiment stronger intermolecular forces and have a higher vapor pressure.
b. will experience stronger intermolecular forces and have a lower vapor pressure.
c. will experimence weaker intermolecular forces and have a higher vapor pressure.
d. will experience weaker intermolecuular forces and have a lower vapor pressure.
2. If volatile liquid is added to a sealed flask, the total pressure inside the flask is a sum of the air pressure and the vapor pressure of the liquid. Consider a flast at 298K with an air pressure of 731. mmHg to which some n-butanol is added. If the measured pressure after the addition is 737. mmHg, what is the vapor pressure of n-butanol at 298K?
3. Now, if the temperature inside the same flask is increased to 328 K, the measured pressure will increase to read 852. mmHg. This is because both the air pressure and the vapor pressure of n-butanol will increase. The air pressure at 328K can be calculated from its value at 298K by using Pi/Ti=Pf/Tf
(a) What is the value of the air pressure at 328 K (in mmHg)?
(b) Using the last result and the measured pressure at 328 K, what is the vapor pressure of n-butanol at 328K?
Explanation / Answer
1] b
2] Total pressure = Air pressure + vapor pressure of the liquid
737 = 731 + Vapor pressure of butanol
Vapor pressure of butanol = 6 mm Hg
3] At T = 298 k
731 and 7 mm Hg
a] for air pressure ,
731 / 298 = Pf /328
Pf = 804.59 mmHg
b] for Vapor pressure of butanol ,
Total pressure = 852 mmHg = Vapor pressure of butanol + Air pressure
Vapor pressure of butanol = 852 - 804.59 = 47.41 mmHG
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