Name ________________________________
Molar Volume – Gas Law Lab 1
Period
Avogadro’s hypothesis is one of the most important gas principles. The principle states: equal
volumes of all gases under the same conditions (same temperature and pressure) contain the same number
of molecules. In other words, if samples of different gases at the same conditions contain the same
number of molecules, then the volume of all gas samples must be equal. Assume that one mole of gas is at
standard conditions, that is, 1 atmosphere and 273.15 K. Then the molar volume of the gas could be
determined by using the combined gas law.
The purpose of this lab is to experimentally determine the molar volume of a gas using the
combined gas law. Carbon dioxide will be allowed to sublimate (the physical change of a solid changing
directly to a gas without appearing in the intermediate liquid phase). Both the volume and mass of the gas
will be determined using the density formula - mass divided by volume. The density of air is 1.29 g/L. The
percent error will then be determined using the theoretical value of 22.4 L.
Safety
 Dry ice can cause frostbite. Wear appropriate insulated gloves or use tongs.
 Do not stopper the flask until all dry ice as sublimed. Failure to observe this precaution may cause
the flask to shatter due to pressure.
 Wear chemical splash goggles, and a chemical resistant apron.

Materials
 Dry ice (solid carbon dioxide), small piece,
 graduated cylinder, 100ml
approximately ¾” cube
 Balance
 Flask, 125ml
 Tongs
 Stopper, solid rubber to fit flask
 petri dish
 2 pipettes
Procedure
1. Mass a dry and stoppered Erlenmeyer flask to the nearest 0.01 grams. Record the mass in the data
table. (Remember: the flask is not empty; it contains air.)
2. Using tongs, place a small piece (dime size) of dry ice in the Pyrex Erlenmeyer flask. Do not stopper
the flask at this point.
3. Gently swirl the flask to aid in the sublimation of the dry ice. While you are waiting, get 2 dime size
pieces of dry ice and place into the petri dish. Using the pipette, add a drop of cold water to one
piece and a drop of warm water to the other piece. Record your observations.
4. Immediately after the solid dry ice in the Erlenmeyer flask has disappeared, tightly stopper the
flask. Mass again. Record the mass in the data table.
5. Remove the stopper and fill the Erlenmeyer flask with tap water up to the top rim of the flask.
Stopper the flask. Wipe off any water on the outside of the flask. DO NOT WEIGH THE FLASK.
6. Unstopper the flask. Carefully pour the water into a large graduated cylinder to measure the volume
of water. The volume of the water is equal to the volume of the flask or volume of a gas in the flask.
Record the volume (convert to liters) in the data table.
7. Record the room temperature in Kelvin and the atmospheric pressure in the data table.
8. Clean up by adding 50 ml of warm water and a drop of soap to your flask. Then add a small piece of
dry ice. Grab some of the bubbles that form and put your hand together. Record what happens.
Clean up Stamp
Data Table
Mass of stoppered flask and air (M1)
Mass of the stoppered flask and CO2 (M2)
Volume of flask (V1)
Room Temperature (T1)
Atmospheric Pressure (P1)
g
g
liters
K
in Hg
Qualitative observations of hot and cold water
Qualitative observations of soap, warm water, and dry ice
Data Analysis
1. Use the density formula to determine the mass of the air. Remember to look in the lab introduction
for the density of air and the density formula. The volume of air (V1) can be found in your data table.
2. Determine the mass of the empty stoppered flask. Subtract the mass of air calculated above from
the mass of the stoppered flask and air (M1) in the data table.
3. Determine the mass of the carbon dioxide. Subtract the mass of the empty stoppered flask as
calculated in the previous question from the mass of the stoppered flask and carbon dioxide from
the data table (M2).
4. Determine the volume of carbon dioxide at STP using the combined gas law. Use the volume (V1),
temperature (T1), and pressure (P1) from the data table as the original conditions, then use standard
temperature (T2), and standard pressure (P2) to find the volume (V2) of the carbon dioxide at STP.
5. Calculate the experimental molar volume using the equation below:
Vexp’t molar = V previous question x molar mass of carbon dioxide
Mass of carbon dioxide you calculated in #3
6. Use the formula for percent error (yes, look it up if you don’t remember), your expt’l molar volume
(answer from question #5), and the theoretical value 22.4 L to determine your percent error.
7. What are sources of error? The higher your percent error the more explaining you have to do!
Name ________________________________
Molar Volume - Gas Law Prelab
1.
What are the conditions of STP?
Period
Std T = _______________, and Std P = __________________
2. What is the purpose of this lab?
___________________________________________________________________________
___________________________________________________________________________
3. What gas law will be used in your calculations? (write the formula) __________________________
4. What are the safety precautions?
___________________________________________________________________________
___________________________________________________________________________
5. What is the formula for percent error (do not use the word error in the formula, find the complete
formula)?
6. What units will the volume be measured in? ____________
7. What is standard pressure in inches Hg? ____________
8. How many liters are in 189 mL? ____________