Question

**A student observes that a 126 mL dry flask with a foil
cup weighs 50.162 g. The student then adds 5 mL of an unknown
volatile liquid and heats flask in a boiling water bath at 99.2 C
Until all liquid disappears. The flask, foil, and unknown after
heating that is dry and cool weigh 50.610 g. The barometric
pressure in the laboratory is 743.3 mmHg; the laboratory
temperature averages 22.3 C; the vapor pressure of the unknown
liquid is 160 mmHg at 20 C and the density of dry air at STP is
1.2929 g/L.**

**a. what are the experimental conditions of T and P that
will be used to Calculate the mass of air in the
flask?**

**b. Calculate the density of air at the experimental
conditions identified in part A.**

**c. Calculate the mass of air in the flask before the
liquid was added.**

**d. Calculate the partial pressure of air in the flask
after the liquid was heated and then cooled.**

**e. Calculate the mass of air in the flask after the
liquid was heated and then cooled.**

**f. Calculate the mass of air lost.**

**g. Calculate the mass of liquid, vapor, and air in the
flask before you correct for air lost.**

**h. Calculate the mass of liquid, vapor, and air in the
flask after you correct for air lost.**

**i. Calculate the molar mass of the unknown
liquid.**

Answer #1

A student was assigned the task of determining the identity of
an unknown liquid. The student weighed a clean, dry 250-mL
Erlenmeyer flask. The student completely filled the flask with
water. He then proceeded to weigh the flask containing the
water.
Mass of 250-mL Erlenmeyer flask: 78.639 g
Mass of 250-mL Erlenmeyer flask and water: 327.039 g
Assuming the density of water is 1.00 g/mL at ambient
temperature, what is the exact volume (in mL) of the 250-mL
Erlenmeyer flask?...

1.A) A student used the method MM=g*R*T/P*V for determine the
molar masss of an unknown volatile liquid. The barometric pressure
in the lab was 746 mmHg, and the temperature of the boiling water
was 98.5 degress C. The mass of the flask was 68.471 g, and the
weight of the flask plus the condensed vapor was 687.959 g. The
volume of the flask was 135.7 mL. What is the molar mass of the
compound?
B) What would happen to the...

A) To a 1L flask that contains air at a pressure of 101 kPa a
small amount of liquid is added. The pressure in the flask after
the addition of the liquid is 107 kPa. What is the vapor pressure
of the liquid?
B)The slope in a plot of lnPvap vs. (1/T) for an
unknown liquid is found to be -1,141. What is the value of
ΔHvap for the liquid in units of kJ/mol?
C)A 5 mL sample of an...

A flask with a sample of gas at room temperature and pressure
weighs 97.4842 g. The same flask with air (density = 1.17 g/L)
weighs 96.8848 g. The same flask filled with water (d = 0.998 g/mL)
weighs 345.86 g. The pressure in the room is 0.989 atm and the
temperature is 22.2 °C.
1. Calculate the volume of the flask.
2. Calculate the mass of the air that the flask can hold.
3. Calculate the mass of the empty...

A 1.15 −g sample of dry ice is added to a 745 −mL flask
containing nitrogen gas at a temperature of 25.0 ∘C and a pressure
of 720 mmHg . The dry ice is allowed to sublime (convert from solid
to gas) and the mixture is allowed to return to 25.0 ∘C. What is
the total pressure in the flask?

A sample of an unknown liquid is vaporized in a flask having a
volume of 298 mL at 100.0°C. The vapor has a mass = 0.687 g, and
exerts a pressure = 775 torr. Calculate the gram molecular weight
of the unknown liquid.

If 1.00 mL of water is placed in a 5.00 L closed flask at 26°C,
what volume of water would remain as liquid after equilibrium is
allowed to establish between the liquid water and the water vapor
in the flask ? (The vapor pressure of water at 26°C is 25.2 torr,
and the density of water at 26°C is 1.00 g/mL.)

A student received a sample of an unknown liquid, which is then
vaporized in a flask having a volume of 250 mL at 80.7 °C. The
vapor has a mass = 0..7179 g, and exerts a pressure = 753 torr.
Using the following list of volatile liquids, determine which one
is the sample examined by the student.
Possible samples:
Methanol (CH4O)
Isopropanol (C3H8O)
Ethyl acetate (C4H8O2)
Cyclohexane (C6H12)
Acetone (C3H6O)

Weight of flask and cover 128.7g
Weight of flask with vapor 129.4g
Pressure of vapor, mm Hg 760
Pressure of, atm 1
Mass of water in flask 250g
Temperature of water in flask (boiling water) =92c
Temperature of vapor in K= 92C+273=365K
Temperature of water in the flask= 25t
the volume of vapor in the flask 250 ML
Using the volume of the flask (in liters) the temperature of the
boiling-water bath (in kelvins), and the barometric pressure (in
atmospheres),...

A 0.90 g sample of liquid water was introduced into an evacuated
2.00 L flask, which was then sealed and
heated to 37°C. What percentage, by mass, of the water remained
as liquid? [Vapor pressure of water at 37°C=48.2 torr.]
A)0%
B)82%
C)90%
D)18%
E)10%

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