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Unformatted text preview: up with varying diameters (a minimum of three straws total for each
person in the group). Place these on a clean paper towel until you are ready to use them. Do not
allow the straws to come into direct contact with any lab surface.
2. If provided, write down the diameter of each straw size, or carefully measure the
diameter of each straw and record these diameters in cm in the report sheet. Keep careful track
of the side of the straws that you used to measure these diameters since they have now
Dakota State University Page 131 of 232 Experiment 10: Gas Laws General Chemistry I and II Lab Manual come in contact with a laboratory ruler. Consider this side of the straw to be
contaminated.
3. Cut the side of the straws that have been measured off of the two longest straws with
scissors such that all three straws are now the same length. Keep careful track of the side of
the straws that have come in contact with the scissors. This is now the contaminated side.
Discard the pieces of the straws that have been removed.
4. Have your lab partner time you for this part; with the smallest straw first, draw in a
deep breath, and time how long it takes you to exhale completely through that straw. Try to
exhale as rapidly as possible. Be careful not to allow yourself to pass out or cause physical harm
by trying to blow too hard. If you cannot exhale completely (you run out of breath too soon),
take the time your partner measured and record it as “>time”, to indicate that it takes longer than
the time recorded.
5. Repeat step 4 for all straws.
6. Have your partner(s) repeat this part of the experiment beginning from step 3.
Calculations:
Boyle’s Law:
Calculate the radius of the plunger from its diameter (radius=diameter/2). Convert from
cm to inches (1 in = 2.54 cm). For simplicity of calculation, we assume the plunger is flat (even
though we know it is not). Therefore, we can calculate the area of the plunger as A= π r2 , where r
is the radius of the plunger in inches and π is about 3.141592654.
Convert the mass of the object into pounds, lb (1 kg = 2.2046 lb). To calculate the
pressure exerted by the mass, simply divide the weight of the object in pounds by the area of the
plunger in square inches (psi). Convert from psi into atmospheres (1 atm = 14.696 psi).
The total pressure on the gas trapped in the syringe is the pressure exerted by the mass
(see above) plus the pressure exerted by the atmosphere, which we will assume to be 1 atm.
Thus, for total pressure, put in the pressure exerted by the mass plus one. On a clean piece of
graph paper, carefully plot the volume of the gas (y axis) versus the total pressure (x axis). Draw
the best straight line that you can through the experimental points.
Take the inverse of each pressure and fill in the column 1/Pressure. On a clean piece of
graph paper, carefully plot the volume of the gas (y axis) versus 1/Pressure (x axis). Draw the
best straight line that you can through the experimental points. Calculate the slope of this line.
Thi...
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 Fall '11
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 Chemistry, pH, The Crucible

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