EXPERIMENT #9: Gas Laws and Gas-Forming ReactionsIntroduction:
In this experiment you will use experimentation to analysis Boyle’s Law. In addition, you
will do an experiment involving the collection of a gas to determine the percent yield of a gas
Of the different physical states, the properties of gases vary the most with temperature
and pressure. If the temperature of a gas changes the pressure or volume will change as well.
When collecting gases in experimentation, a sealed container is necessary so that the gas does
not escape. There are several different gas laws that help describe the behavior of gases.
One gas law is known as Boyle’s Law, which was originally published by Robert Boyle
in 1662. Robert Boyle found that the pressure of a gas and the volume of a gas are inversely
proportional as long as amount and temperature are held constant. In other words, as the pressure
of a gas increases the volume will decrease. The following equation is the mathematical
expression for Boyle’s Law:
𝑃1 𝑉1 = 𝑃2 𝑉2
In this experiment the pressure of the syringe initially is equal to the room pressure,
however once the weights are put on the plunger the pressure in the syringe decreases. In order to
calculate the pressure in the syringe once the weights have been put on the plunger the following
equation must be used:
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒𝐹𝑖𝑛𝑎𝑙 = 𝑅𝑜𝑜𝑚 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 − 𝑀𝑎𝑠𝑠 𝑜𝑛 𝑃𝑙𝑢𝑛𝑔𝑒𝑟 × 0.1561 𝑎𝑡𝑚/𝑘𝑔
Another gas law used in this experiment, is arguably the most important. The ideal gas
law allows us to determine either the pressure, amount, volume, or temperature of a gas if we
know all the other values. In this experiment we will know the pressure, temperature, and
volume of the gas, we will then use the ideal gas law to determine how many moles of gas were
formed from a chemical reaction. The ideal gas law is often used when doing stoichiometry for a
chemical reaction that involves gases. The following is the equation for the ideal gas law:
𝑃𝑉 = 𝑛𝑅𝑇
In this equation P is for pressure and must be in atm, V is for volume which must be in
liters, n is moles of gas, R is the ideal gas constant which is 0.08206 𝑚𝑜𝑙∙𝐾, and T is for
temperature which must be in kelvins. If in a chemical reaction one of the products or reactant is
a gas and is described using the pressure, temperature, and volume the ideal gas law can be used
to determine the moles of gas present and then using moles you can then solve a stoichiometry
problem. Otherwise, stoichiometry might be needed to find moles of a specific gas, so that the
volume, pressure, or temperature of a gas could be determined. In this lab the reaction of sodium
bicarbonate with hydrochloric acid is investigated, the equation for this reaction is seen below:
𝑁𝑎𝐻𝐶𝑂3 (𝑠) + 𝐻𝐶𝑙(𝑎𝑞) → 𝑁𝑎𝐶𝑙(𝑎𝑞) + 𝐻2 𝑂(𝑙) + 𝐶𝑂2 (𝑔)
Instructor Demonstration: Invisible Can Crush
1. First take a soda can and add a small amount of water to it.
2. Place the soda can on a hot plate and turn it up so that the water will begin to boil.
3. Then make an ice bath in a small bowl, and once the water in the can is boiling using
beaker tongs quickly flip the can over into the ice water.
Experimental Procedure: Boyle’s Law
1. Obtain a 60 mL syringe and a syringe cap, ensure that plunger is lubricated. Set the
syringe to 25 mL and attach the syringe cap. Make sure the cap is screwed tight and
the syringe is sealed tight by pushing the plunger in just a little and checking to make
sure it moves back to 25 mL.
2. Using a two or three prong clamp secure the syringe on a ring stand relatively high up
with the plunger pointed down. Then attach your test clamp onto the plunger. Place a
1 kg weight on the test tube clamp. See picture below.
3. Gently tap the syringe so that the volume stabilizes. Record the volume on the
4. Add a second 1 kg weight to the previous weight and record the volume a second
5. Calculate what the volume should have been using Boyle’s Law with the initial
pressure, initial volume, and final pressure, for when there was only a 1 kg weight on
the plunger and when there was a 2 kg weight on the plunger.
6. Using the measured volume and the actual volume from Boyle’s Law calculate the
percent error of the measurement.
Apparatus for Boyle’s Law Experiment
Experimental Procedure: Reaction of Baking Soda and Acid
Safety: 6M HCl, is hazardous to your skin and can cause burns and irritation, avoid
contact with your skin, by wearing gloves. If HCl does come in contact with your
skin wash the affected area with DI water for 15 mins.
1. Obtain an Erlenmeyer flask with spigot, a thick-walled test tube, two stoppers with
rubber hosing, and a gelatin capsule from the cart. (There are two different stoppers
with rubber hosing you need one of each).
2. Fill the Erlenmeyer flask with about 100 mL of deionized water, attach the rubber
hose with the smaller stopper and glass tube attached to it to the spigot on the
3. Put the stopper with the longer glass or metal tube and the bigger stopper into the top
of the Erlenmeyer flask. Make sure both the hose and the stopper are well sealed.
4. Put the end of the hose coming from the top of the Erlenmeyer flask. Then attach a
pipette pump to the end of the glass rod that is attached to the hose on the spigot of
the Erlenmeyer flask and apply suction until the water in the flask raises to about 1
cm below the spigot. Clamp the hose with the pump on it with a hose clamp.
5. Empty the beaker of water and measure the mass, there is no need to fully dry the
6. Measure the mass of the gelatin capsule empty, then begin to add sodium bicarbonate
into the capsule until there is about 0.3-0.4 grams of sodium bicarbonate in the
capsule, record the mass of the capsule and sodium bicarbonate.
7. Clamp the test tube on a ring stand with a two or three prong clamp. Then measure
out about 10 mL of 6 M HCl with a graduated cylinder, and pour it into the test tube.
8. Place the gelatin capsule with sodium bicarbonate in it, into the test tube make sure it
is touching the HCl solution. Place the stopper connected to the spigot into the test
tube tightly, and remove the hose clamp. Water will begin to flow into the beaker
once the reaction starts.
9. Measure the mass of the beaker with the water in it and record the temperature of the
water in the beaker.
Apparatus set up for Reaction of baking soda and Acid.
Instructor Initials: _________
Experiment 9: Gas Laws and Gas-Forming Reactions
Instructor Demonstration Observations:
What happened in the demonstration to the soda can, and why did it happen?
What gas law is being demonstrated in what you saw?
Data and Calculations:
2 kg Weight
Initial Volume of Syringe:
Final Volume of Syringe:
Initial Pressure in Syringe
(provided by instructor):
Final Pressure (actual pressure):
(Calculated using mass equation)
Final Pressure (measured pressure):
(Calculated using Boyle’s Law)
Percent Error in Final Volume:
Reaction of Baking Soda and Acid:
Mass of Gelatin Capsule empty:
Mass of Gelatin Capsule with sodium bicarbonate:
Mass of empty Beaker:
Mass of Baking Soda Used:
Mass of Beaker with Water:
Temperature of Water in Beaker:
Density of Water:
Mass of Water in Beaker:
Volume of Gas Formed:
Pressure of CO2 (Provided by Instructor):
Mass of CO2 Gas formed (Calculated using Ideal Gas Law):
Theoretical Yield of CO2 Gas:
Experiment 9: Post-Lab Assignment
1. What are some possible reasons for the percent error you measured in the Boyle’s Law
part of the experiment?
2. What could be some reasons your percent yield for the decomposition reaction was not
3. The decomposition of sodium azide is commonly used in car airbags, when the sodium
azide decomposes it forms nitrogen gas which inflates the air bag. If you want to make
60.5 L of nitrogen at 25.0 °C, and 1.00 atm of pressure from this decomposition reaction,
how many grams of sodium azide (NaN3) would need to decompose? Use the following
𝑁𝑎𝑁3 (𝑠) → 𝑁𝑎(𝑠) + 𝑁2 (𝑔)
4. If a balloon initially has a pressure of 1.456 atm and a volume of 1.32 L, what would be
the pressure after the volume decreases to 0.543 L?
5. If a syringe with a plunger has a volume of 56.2 mL at 25.0 °C, what would the volume
be if the temperature was changed to -15.6 °C?
Experiment 9: Pre-Lab Assignment
1. What two gas laws are being used in the experiment?
2. What is the equation for percent error used in the Boyle’s law part of the experiment?
(We used this equation in Experiment 1)
3. About how many grams of sodium bicarbonate will be used in the decomposition of
baking soda part of the experiment?
4. If the initial pressure of a container is 0.658 atm and the initial volume is 35.6 mL, what
will be the pressure if the volume is decreased to 15.8 mL?
5. Using the equation in the introduction, determine what the pressure within the syringe
would be if the initial pressure in the room is 1.013 atm and a 1.5 kg weight has been
added to the plunger of the syringe.
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