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Chapter 5 answers
At 25
o
C a sample of He has a volume of 4.00 x 10
2
mL under a
pressure of 7.60 x 10
2
torr.
What volume would it occupy under a pressure of 2.00 atm at the same T?
()
()
mL
10
00
.
2
torr
1520
mL
400
torr
760
P
V
P
V
V
P
V
P
2
2
1
1
2
2
2
1
1
×
=
=
=
=
A sample of hydrogen, H
2
, occupies 1.00 x 10
2
mL at 25.0
o
C and 1.00 atm.
What volume would
it occupy at 50.0
o
C under the same pressure?
It is CRITICAL to convert ANY temperature to KELVIN!!
T
1
= 25 + 273 = 298 K
T
2
= 50 + 273 = 323 K
mL
108
K
298
K
323
mL
10
1.00
=
V
T
T
V
=
V
T
V
T
V
2
2
1
2
1
2
2
2
1
1
=
×
×
∴
=
If we have a 2.5L of a gas at 25°C and 1.5atm, and we increase the temperature by 100 °C and
find the pressure is now 800 torr, what is the new volume?
P
1
= 1.5atm
P
2
=800torr * 1atm/760torr = 1.053atm
V
1
= 2.5L
V
2
= ?
T
1
= 25°C=25+273.15K=298.15K
T
2
= T
1
+100°C = T
1
+ 100K = 398.15K
Sub these in to the combined law above:
1.5atm*2.5L
= 1.053atm*V
2
298.15K
398.15K
V
2
= 4.76L
A sample of nitrogen gas, N
2
, occupies 7.50 x 10
2
mL at 75.0
0
C under a pressure of 8.10 x 10
2
torr.
What volume would it occupy at STP?
()
()
(
()
(
)
)
mL
627
K
348
torr
760
K
273
mL
750
torr
810
T
P
T
V
P
=
V
for
Solve
torr
760
=
P
torr
810
=
P
K
273
=
T
K
348
=
T
?
=
V
mL
750
=
V
1
2
2
1
1
2
2
1
2
1
2
1
=
=
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View Full DocumentA sample of methane, CH
4
, occupies 2.60 x 10
2
mL at 32
o
C under a pressure of 0.500 atm.
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 Fall '07
 Fakhreddine/Lyon

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