Transcript Molecules In A Box - Poudre School District

Gas Laws Continued
Atmospheric Pressure
Let’s calculate the
amount of
atmospheric
pressure pressing
on our bodies!
 Step 1: Calculate
body surface area.
 Use this equation:

M2 = (Ht in Cm)0.3964 x (Wt in Kg)0.5378 x 0.024265
Atmospheric Pressure
Conversions: 1in = 2.54 cm
1lb = .45 Kg
 Step 2: Next convert Meters2 into
Inches2.

– One Meter = 39.36 Inches.
– 1M2 = 1550 In2.
Step 3: Multiply your answer from step one
with step two.
 Step 4: Multiply your answer from step 4
by 13.0 psi (PSI in Fort Collins)

Example

Height = 69 in
– 175.26 cm

Weight = 130 lbs
– 59 Kg



(175.2cm)0.3964 x (59Kg)0.5378 x0.024265= 1.676 M2
1.676M2 x 1550 in2 = 2597.8 in2
2597.8in2 x 12.5psi = 32,472.5 lbs
32,500.00 Lbs
Put it into Perspective
This is the same as
three full grown
elephants.
 This is the same as
12 Honda Civics.
 This is the same as
one semi-truck.

Ideal Gas Law
The Ideal Gas Law allows us to
account for the number of moles of
gas in a system.
 The Ideal Gas Law automatically
adjusts to standard temperature and
pressure using the Ideal Gas
Constant (R).

Ideal Gas Law
PV=nRT



Pressure is
proportional to
temperature. (T)
Pressure is
proportional to number
of moles. (n)
Pressure is inversely
proportional to
volume. (V)
The Universal Gas Constant
R is the universal gas constant that
corrects for systems not at STP.
 The value of R varies depending on
which units of pressure are being
used.
 R = 0.0821 L  atm/mol  K
 R = 62.4 L  mmHg/mol  K
 R = 8.31 L  kPa/mol  K

Dalton’s Law


John Dalton
(1766-1844)
At a constant volume
and temperature, the
total pressure exerted
by a mixture of gases
is equal to the sum of
the partial pressures
of those gases.
Dalton’s Law
Each gas exerts its own pressure as
if the other gases were not there.
 You can add the individual pressures
of each gas to obtain the total
pressure of a gas mixture.
 Mathematical Expression

– Ptotal=P1+P2+P3+P4…………
The “Litter Box” Equation
 = dRT/P
A useful version of the Ideal Gas Law
involved molar mass and gas density.
 If gas density (d in g/L) is known,
molar mass ( in g/mol) can easily be
calculated.
 We call it the “litter box” equation
because a kitty says “mu”, takes a “P”,
and kicks “dRT” over it.

Review
Which line on the
graph at the left
best illustrates
Boyle’s Law of
pressure and
volume?
 If you said “D”, you
are correct!

B
V
o
l
u
m
e
A
C
D
Pressure
Review
Which line on the
graph shows
Charles’ Law, the
relationship
between
temperature and
volume?
 If you said “A” you
are correct.

B
V
o
l
u
m
e
A
C
D
Temperature
Review
P
r
e
s
s
u
r
e
Which line best
illustrates GayLussac’s law of
pressure vs.
temperature?
 If you said “A”
again, you are
correct.

B
A
C
D
Temperature