Avocado

Proving Avogadro’s Law

By Kevin Li, Peter Yu, and Ashwin Sreevatsa

What Is Avogadro's Law? ● Avogadro's Law was discovered by Amedeo Avogadro in the early 1800s. ● Avogadro's Law describes the relationship between volume and the amount of a substance. ● Volume and the amount of a substance - measured in moles - have a direct relationship. This means that as volume increases, the amount of a substance will also increase and vice versa. ● Note, however, that this relationship ONLY holds true if the pressure and temperature are held constant. ● This relationship can be represented by the equation: V1/n1 = V2/n2 - where V is the volume and n is the amount of the gas, measured in moles.

Cool Fact: Avogadro sounds like “Avocado”

Proving V1/n1 = V2/n2 Experiment Materials: 1. Syringe (with volume scale) 2. Syringe Stopper Add-on (to seal the balloon and syringe) 3. Balloon 4. Scale 5. Air

1

â—?

5

4

3

2

Experiment Procedure 1. Zero the scale with the empty balloon.

2. Attach balloon to the stopper.

3. Attach the stopper with the balloon to syringe.

Experiment Procedure (Cont’d) 4. Pump 300 mL of air with the syringe into the balloon; this may take several pumps.

Experiment Procedure (Cont’d) 5. Tie up the balloon so that no air escapes, then weigh the balloon on the scale and record the mass data.

Experiment Procedure (Cont’d) 6. Untie the balloon and let out the air.

7. Repeat steps 2-6 by pumping air into the balloon to the amounts of 600 mL, 900 mL, and 1500 mL. 8. Clean up station.

9. Convert the masses into moles using the formula n=m/M where n is the number of moles, m is the mass, and M is the molar mass of air. The average molar mass of air is 28.97 g/mol.

10. Plug in the corresponding mole and volume amounts into Avogadro’s Law equation: V1/n1 = V2/n2 and check if the two equations equal each other.

Data Volume 0mL (0L)

Number of Molecules (mol)

Mass (g)

Molar Mass (g/mol)

V/n

0

0

n/A

300mL ( 0.3L) 0.0003451846738

0.01

900 L/mol

600mL (0.6L) 0.0006903693476

0.02

900 L/mol

900mL (0.9L)

0.001035554021

0.03

900 L/mol

1500mL (1.5L)

0.001725923369

0.05

900 L/mol

28.97

Analysis The experiment shows how when gas was added to the balloon, the volume increased.

For each of the data points, V/n ended up being 900 L/mol, thus showing that V/n is constant and proving Avogadro’s Law. The graph illustrates the direct relationship between volume and amount of gas.

As more gas is added to a flexible container, the internal pressure will be greater than the external pressure, so the container will expand to reach the equilibrium point between pressures, causing an increase in volume.

Possible Sources of Error ● Since some air escapes the balloon as the balloon is taken off of the syringe, the mass (which is measured after the balloon is taken off) would be slightly less in proportion to the volume (which is measured before the balloon is taken off). ● Since the syringe measures in increments of 1 mL, the volume measurements could have been imprecise. ● Since the scale measures in increments of 0.01g, the mass measurements were probably very imprecise, considering the differences in measurements are about 0.01g as well.

This leaves considerable margins of error from ±10% for the largest measurement to ±50% for the smallest measurement.

Applications In Real Life Avogadro’s Law is present in almost all aspects of life. For example: 1. Lungs: Avogadro’s law explains how our lungs work.

As we take in more air, our lungs expand, and we’re able to breathe.

2. Tires: When more air is pumped into a tire, its volume expands, allowing it to roll stably.

Reflection From the experiment, we learned how Avogadro’s Law works in a real life scenario, and how volume and the amount of gas are related.

Even an experiment as simple as ours had complications.

We learned from this to keep our experiment ideas as simple as possible for the next time to reduce obstacles.

The experiment could be made better by using a larger syringe, since the smaller syringe had to be refilled with air multiple times for the balloon to reach the desired volume, leading to measurement error.

The experiment could also be improved with a more accurate scale, since our scale could only measure up to the hundredths place in grams, and air’s light weight makes it difficult to get an accurate measurement.

Bibliography http://www.glogster.com/solrose/chemistry-lecture/g6m1op2qdm07fdq146gvila0 - Pic of Avogadro http://www.engineeringtoolbox.com/molecular-mass-aird_679.html - Molar mass of air https://authoritynutrition.com/12-proven-benefits-ofavocado/ - Pic of Avocado http://www.maplecityrubber.com/wpcontent/themes/maple_city/images/balloon_blue.png Pic of balloon https://pixabay.com/en/syringe-injection-hospital-needles1135225/ - Pic of syringe https://simple.wikipedia. org/wiki/Weighing_scale#/media/File:Balance_Kern.jpg Pic of scale http://cnx. org/resources/26776b591c6ee8a133e6c8a9cb2db13cd4 d3dd00/Figure_39_03_03.jpg- Pic of lungs