Transcript Kitchen Science - Chemistry Land Intro

Putting Gases
to Work
Cracking under pressure
Pumps 1 ½” water stream 260 feet.
Gas:
Alteration of Latin chaos space, chaos Date: 1779
The gas engine is one of the wonders of the 19th
century. Now, within three years of the 20th
century, it is a novel machine, eagerly sought by
many people. It is thought by persons who have
not studied its principles that it is a steam-engine,
using gas or gasoline as fuel for the purpose of
making steam. This is erroneous. Gas and
gasoline in specific proportion with air are
explosive material.
It is only a matter of time when the prejudice that,
as usual, exists against any innovation, the
ungrounded fear of explosions and other
difficulties, will be overcome and the superiority of
the gas engine over the wasteful steam engine
and boiler will be established.
The unsightly smoke stacks, belching forth smoke and soot, will
be relegated to the scrap heap. The atmosphere of our
manufacturing cities will be as clear as that of the country.
In the next decade the steam engine will occupy the
same relative position to the gas engine that the flint
and steel now do to the lucifer match.
the tallow dip to the electric light...
...the stage coach to the modern electric
street cars, and civilization will record another
grand stride toward the millennium.
9 hits
9 sec
=
1 hit
sec
0
Seconds
9
18
18 hits
9 sec
=
2 hits
sec
00
01
02
03
04
05
06
07
V=0.5
, P=2
V=6
, P=5
V=0.1,
P=10
V=3,
P=10
V=10, P=2
P=0.1
V=30,
27 ºC = 300 K
9 hits
9 sec
=
1 hit
sec
0
Seconds
9
18
27 ºC = 300 K
18 hits
9 sec
=
2 hits
sec
00
01
02
03
04
05
006
K
07
327 ºC = 600 K
9 hits
4.5 sec
=
2 hits
sec
327 ºC
= 600 K
0
Seconds
9
18
27 ºC = 300 K
00
01
02
03
04
05
006
K
07
15 psi, 300 K
30 psi 600 K
3 psi
60 K
1 psi
20 K
15 psi, 2 L, 300 K
30 psi 2 L 600 K
6 psi 1 L 60 K
3 psi 2 L 60 K
2 psi
1L
20 K
1.4 x 1.4 = 2
2 x 2 =2
1.5 x 1.33 = 2
doubles
• P is pressure measured in atmospheres.
• V is volume measured in Liters
• n is moles of gas present.
• R is a constant that converts the units. It's value is
0.0821 atm•L/mol•K
• T is temperature measured in Kelvin.
• Simple algebra can be used to solve for any of these
values.
• P = nRT V = nRT
n = PV
T = PV R = nT
•
V
P
RT
nR
PV
•
•
•
•
•
Pressure=1 atmosphere
Volume=1 Liter
n = 1 mole
R=0.0821
What is the temperature?
What pressure could be reached when ¼
lb of dry ice is placed in this 2 liter bottle?
Temperature that night was 86 °F (30 °C)
Facts:
2 Liter bottle
¼ lb = 454 g ÷ 4 = 114g
PV = nRT or
P = nRT
V
CO2= 12g/mol + 2*16g/mol = 44 g/mol
114 g 1 mol = 2.6 mol
44 g
What pressure could be reached when ¼
lb of dry ice is placed in this 2 liter bottle?
Temperature that night was 86 °F (30 °C)
n
P=
R
T
2.6 mol x 0.0821 atm*L x 303 K
mol*K
2.0 L
V
P = 32.3 atmospheres
32.3 atm 14.7 psi = 475 psi
1 atm
CONVERSIONS
•
•
•
•
•
•
•
•
•
760 mm of Hg
760 torr
All
29.9 in. of Hg
Equal
1 Atmosphere
14.7 lbs. per sq. in.
Temperature conversions:
Evangelista Torricelli
Kelvin = Celsius + 273
OC = (OF -32) x 5/9
OF= OC x 9/5 + 32
When a pressure cooker is used, what
causes the increased pressure?
PV=nRT
P=nRT
V
Temperature goes from 25oC to 100oC
Turn to Kelvin by adding 273 to Celsius
297K to 373K 75K/297K=25% increase in pressure

Temp C
0
75K / 297K= 25% 297K 25
50
373K 100
110
120
130
140
150
170
180
190
200
PSI
0.089
0.458
1.779
14.700
20.800
28.800
39.100
52.400
69.000
114.900
145.400
182.000
225.000
mm Hg
5
24
92
760
1075
1489
2021
2709
3567
5940
7517
9410
11633
inches Hg
0
1
4
30
42
59
80
107
140
234
296
370
458
Water vapor pressure
250.000
PSI
200.000
150.000
Series1
100.000
50.000
0.000
0
100
200
Temperature Celsius
300
• You are on a camping trip and one tire has a slow leak. Finally it
goes flat and you don’t have a spare tire. You suggest crushing
some of the dry ice you had brought along and funneling it into
the tire through the tire valve. How many grams of dry ice would
you need to blow up a tire with a volume of 80 liters and
pressure of 32 psi? Current temp is 25OC.
• Change 32 psi to atm and 25OC to Kelvin
• 32 psi x 1 atm = 2.177 atm
14.7 psi
• 25OC= 273+25=298 K
• Solve PV=nRT for n (moles) n = PV
RT
• n = 2.177 atm x 80 Liters
•
0.0821 atm•L/mol•K x 298K
• n = 7.118 moles > 7.118 mol x 44.01 g/mol = 313.3 g or 310 g
• 310 g x 1 lbs per 453 grams = 0.68 lbs.
P1V1=n1RT1
P2V2=n2RT2
n1T1 n1T1
n2T2
P1V1= R
P2V2= R
n1T1
P1V1= P2V2
n2T2
n1T1
n2T2
n2T2
• Molar mass = gRT
•
PV
• 12. In 1984 in a village in the African nation of Cameroon,
1,700 people died from carbon dioxide poisoning when the
nearby lake released huge amounts of CO2. As a early
warning device, a pump could be designed to pump samples of
air into a 4 liter container until the mass of the container grew
by 22 grams. At that point a pressure reading could be taken
as well as the temperature. Let’s say the pressure is 3.1
atmospheres and the temperature is 30OC (86OF). What
molar mass would the device calculate?
• Plug in the values into the equation
• Molar mass = 22 g x 0.0821 atm•L/mol•K x (273+30) K
•
3.1 atm x 4 L
• Molar mass = 44.13 g/mole