Transcript Laboratory 14 A CAPSTONE EXPERIENCE: TOWARD THE CREATION OF AN AUTOMOBILE AIRBAG.

Laboratory 14
A CAPSTONE EXPERIENCE: TOWARD THE
CREATION OF AN AUTOMOBILE AIRBAG
Objectives
1. Integrate general chemistry I concepts to
create a model for an automobile airbag
2. Determine a method and then carry out
appropriate procedures to inflate a bag with
a gas, given a specified set of materials
THREE STATES OF MATTER
General Properties
of Gases
• There is a lot of “free” space in a gas.
• Gases can be expanded infinitely.
• Gases fill containers uniformly and
completely.
• Gases diffuse and mix rapidly.
Properties of Gases
Gas properties can be modeled using
math. Model depends on—
• V = volume of the gas (L)
• T = temperature (K)
• n = amount (moles)
• P = pressure
(atmospheres)
The Ideal Gas Equation
Ideal gas law the functional relationship between the
pressure, volume, temperature and moles of a gas.
PV = nRT
P
V
T
n
R
=
=
=
=
=
pressure
volume
temperature (Kelvin)
number of moles
gas constant
Standard molar volume of an ideal gas
The volume of 1 mol of an ideal gas under
standard conditions,
V = nRT = (1 mol) [0.082057 (L•atm)/(K•mol)] (273.15 K) = 22.41 L
P
1 atm
The volume of 1 mol of an ideal gas at 0ºC and 1 atm
pressure is 22.41 L, called the standard molar volume
of an ideal gas.
Using PV = nRT
How much N2 is required to fill a small
room with a volume of 960 cubic feet
(27,000 L) to 745 mm Hg at 25 oC?
Solution
1. Get all data into proper units
V = 27,000 L
T = 25 oC + 273 = 298 K
P = 745 mm Hg (1 atm/760 mm Hg)
= 0.98 atm
R= 0.0821 L atm / mol K
Now plug in those values and solve for the
unknown.
PV = nRT
4
(0.98 atm)(2.7 x 10 L)
n =
(0.0821 L • atm/K• mol)(298 K)
n = 1.1 x 103 mol (or about 30 kg of gas)
Importance of Gases
• Airbags fill with N2 gas in an
accident.
• Gas is generated by the
decomposition of sodium azide,
NaN3.
• 2 NaN3 ---> 2 Na + 3 N2
•Electronic sensors built into the car detect
collisions, and an electrical impulse is sent
to the air bag, igniting it.
•The air bag itself is made of nylon and
contains very small pores, and will deflate
soon after inflating to allow the passenger
to exit the vehicle.
Your task is to simulate the construction of an air bag using a
ziplock bag, baking soda (NaHCO3) and acetic acid
(HC2H3O2)
The reaction produces carbon dioxide gas , which inflates
the ziplock bag.
NaHCO3(s) + HC2H3O2(aq)  CO2(g) + NaC2H3O2(aq) + H2O(l)
(baking soda) (acetic acid )