Problems 1 find the location of a nearby barometer go

PROBLEMS
1. Find the location of a nearby barometer. Go there and measure the
pressure of the atmosphere. Make a careful drawing of the pointer and
scale on the barometer showing the pressure as you read it.

PROBLEMS
105
If no barometer is available, you can go to almost any weather website
and find the current atmospheric pressure for the nearest weather station.
Now, to run yourself through all these terms and units, make a table
with two rows and eight columns. In the first row label each column with
the name of a unit of pressure. Using the appropriate units, put the value
of the pressure that you measured into each column of the second row.
Why is the number you measured di ff erent from the value of the
“standard atmosphere”?
2. Suppose you have a piston with an area of 100 cm
2
sitting on a volume
of 10 L of nitrogen gas at T = 20
◦
C. If the gas is heated and warmed
to T = 30
◦
C, by how much does the volume change? Give your answer
accurate to ± 1%.
3. Suppose you have a pyrex flask that has a volume of 350 mL at 0
◦
C.
What will be its volume after being heated to 100
◦
C?
4. State the argument by which the ideal gas law is determined. Derive
the ideal gas law from Boyle’s Law and Gay-Lussac’s Law.
5. State the ideal gas law, identify the variables in the law, and use it to
find the pressure of 1 mole of gas contained in a volume of 11.2 L at 0
◦
C.
6. A 45-liter container at room temperature is known to have in it a
total of N = 15 × 10
23
diatomic molecules of oxygen gas.
a. What is the number density n of the molecules of this gas? Give
your answer in units of cm
− 3
.
b. What is the number of moles, n
M
, of this gas?
c. What is the pressure of this gas?
7. An experimenter measures pressure of gas as its volume is changed
and gets the following data:
Pressure (Pa) Volume (m
3
)
1000 1.5
1500 1.0
2000 0.75
2500 –

106
4. GAS LAWS
a. Do these data obey Boyle’s law? Explain how you know.
b. What value of volume would you expect to measure for the missing
entry in the above table?
8. Suppose the above data were taken at a temperature of 27
◦
C and then
later the gas was cooled to − 73
◦
C. At what volume would the cooled gas
have a pressure of 1000 Pa?
9. Consider the following table of measurements of pressure vs. volume
for O
2
( M
O
2
= 32 u) in a closed container at 300 K.
Pressure (kPa) Volume (cm
3
)
90.9 24.89
73.6 30.73
59.5 37.93
a. Is it reasonable to conclude that the gas obeys Boyle’s law? How
did you come to this conclusion? Discuss clearly.
b. How many molecules are contained in this volume? How do you
know?
c. If the oxygen molecules are replaced by an equal number of helium
gas molecules ( M
He
= 4 u) at the same temperature, what would
be the gas pressure when the volume V = 30 . 73 cm
3
? (Hint: See
the above table.)
10. Boyle’s measurement of the air pressure outside his apparatus
(Fig. 4.6 ) was 29
2
16
inches of mercury (Hg). [The density of Hg is ρ
Hg
=
13.6 g cm
− 3
.]
29 2 /
16
"
FIGURE 4.6 Barometer for Problem 10 .