FALL 2006_Studio_6_gases_FINAL - Chem 25 Studio#6 Gases...

Chem. 25: Studio #6 ___ Gases: Pressure, Volume and Temperature
NAME:___________________________ STUDIO:________________________
Relationships of Pressure, Volume and Temperature for Gases
NOTE: THERE IS NO PRE-LAB FOR THIS STUDIO. Homework #6 will give you
sufficient practice with problems involving the gas laws.
In this experiment, you explore two relationships: one between the pressure (P) and
volume (V) of a constant quantity of gas (n) at constant temperature (T), and the second
between the temperature and pressure of a constant quantity of a gas at constant volume.
A series of relationships among these variables was initially studied by Boyle (P and V),
Charles (V and T), Gay-Lussac (P and T) and Avogadro (V and n) and ultimately resulted
in the statement of the ideal gas law: PV = nRT, where R is the universal gas constant
with a value of 0.08206 L atm / K mol. Notice that this expression is referred to as a law
– a statement of generally observed behavior. It describes nature but does not attempt to
describe why nature behaves this way.
Because you use a computer-interfaced probe to acquire the data and the computer to
analyze it, you will be able to explore easily options other than the accepted mathematical
relationships to fit your experimental results. In addition to examining the relationships
among these variables, you’ll get a flavor of how laws arise through the thoughtful
observation of quantitative data. In this Studio we’ll develop the laws that describe how
gases behave; in class we’ll discuss the theory that has been proposed to explain why
gases behave the way they do.
The ideal gas law describes mathematically the generally observed behavior of a gas. If
we reform the ideal gas law like this
R = PV
nT
we can clearly see all the individual gas laws expressed in it. R is constant, and for that
to be the case, P α 1/V (Boyle’s Law), V α T (Charles’ Law), P α T (Gay-Lussac’s Law)
and V α n (Avogadro’s Law). In this experiment, you assess the general behavior of
gases and explore Boyle’s and Gay-Lussac’s laws.
Using the power of modern computers, you can sometimes fit data in a surprising number
of ways and it may become necessary to choose among a number of possible
mathematical descriptions to select the one that best represents the behavior. Although
the concept of ‘best fit’ is actually handled in a rigorous mathematical way, you are
invited to explore possibilities with the data sets you collect in this exercise in a
qualitative fashion just to see how fitting works.
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Chem. 2 5: Studio #6 ___ Gases: Pressure, Volume and Temperature
NAME:___________________________ STUDIO:_______ GROUP: _______
In the lab:
A note about the equipment:
To collect data in this experiment, you use an apparatus that is interfaced to a computer.
The standard arrangement of the equipment is shown in the Fig. 1.
Figure 1: Set-up for computer and probe
The interface reads output voltages from the probe or probes and delivers this
information to the serial port of the computer.