Experiment 11

What is the definition of absolute zero? What is the scientific definition of pressure as it relates to gases? What does this definition imply about the theoretical pressure of an ideal gas at absolute zero? Explain.

Absolute zero is the temperature at which the thermodynamic system has the lowest energy, or at 0K. Pressure is the force exerted per a set unit of area, measuring momentum of molecules of gas as they are moving. At absolute zero no molecules will be moving, so the pressure will be zero, or nonexistent.

Understanding the Experiment Design: If the room we collected data had been more humid, would that affect the analysis of our data?

According to Avogadro's Law, the number of moles of gas remain constant for an ideal gas. This is true at equal pressures, volumes, and temperatures. Our assumption was that the gas molecules present in the containers were ideal gases. The moles of gas molecules should not change due to humidity. The air density and the effective molar mass decreases as humidity increases. We still consider the number of moles of gas molecules and those are not supposed to change

What assumptions about the gases in the air did we make to allow us to calculate your assigned relationship in this experiment?

Assumptions about the gases in the air that allow for the assigned relationship of moles versus pressure to be determined in this experiment were that intermolecular forces do not come into play and that temperature would be help constant. The relation to intermolecular forces comes from the kinetic molecular model to allow for ideal conditions to be assumed. Temperature being held constant allowed for the pressure to be observed and for relationships to be evaluated. In terms of moles, it was assumed that the increase in moles would allow for an increase in opportunity to interact with the walls of the syringe, according to ideal gas laws, which allowed for the expected relationship to be observed.

Directly Proportional:

Directly proportional means that as one variable is increased, so is the other. X/Y=c

Understanding the Experiment: If you were to repeat this experiment, what possible sources of error should you consider for Part D and E

If this experiment were to be repeated possible sources of error to be considered for parts D and E are calibration error within the Vernier data which would result in the data being skewed. Another possible source of error could be the plunger of the syringe being inaccurate so that the measurements would be hard to keep accurate. Both of these would cause for misreading and inaccurate trial data to be produced.

Inversely proportional

Inversely proportional means that as one variable is increased, the other is decreased. XY=C

Think back to Zoom lab, what were the other relationships you explored and were given mock data for? What relationship should we have found?

Other relationships that were observed were pressure versus volume, pressure versus moles, and pressure versus temperature. The expected relationship for pressure and volume is indirect, meaning as one variable increases the other will decrease. The expected relationship for pressure and temperature is direct, both variables will decrease, or both will increase. The expected relationship for pressure and moles is direct, both variables will increase or both will decrease.

Understanding the Experiment: How would having a larger syringe impact the data collected and the analysis?

Pressure will start off at 1 atm prior to the experiment beginning. A larger volume will. be used. Another trend that would occur with this change would be lower observed temperatures due to their direct relationship and linear Vernier graph.

Purpose

The relationship between pressure, volume, and temperature of a gas is being determines, as well as specifics such as pressure and volume and pressure and temperature. The linear relationship of the variables will be observed and the R value is determined and compared to the ideal gas law. Pressure and amount of gas, as well as inverse amount of gas are compared. This will be done to verify gas laws including Boyle's and Gay-Lussac's laws.

How was this relationship derived from this experiment? Full answers will incorporate all relevant data.

The relationship that was derived from this experiment is pressure over moles. The number of moles was determined using density, volume, and molar mass. This number of determined moles was then compared to pressure, showing that as the number of moles increases, pressure will also increase. This demonstrates a direct relationship as seen in the positive slope for the 3 trials, ex: trial 1's slope of 234311 kPamol.

What is the universal gas constant and how does it compare to the values you found in this lab?

The universal gas constant is 8314 L*Pa/K*mol. The value found in the experiment based off of trial 1 was 7913 L*Pa/K*mol. The two values are very similar showing minimal error for the experiment. The universal gas constant is assumed that ideal gas conditions are present, the similarities between the two values allow for the assumption that the experimental data is close to ideal conditions.

Procedure

To begin the lab, 400 mL of water was heated. Then the Vernier GoDirect Gas Pressure Sensor was calibrated and was set to units of atm. An alcohol thermometer was used to record the room temperature and the plunger on the provided syringe was set to 10mL and the initial volume was recorded before it was attached to the gas pressure sensor. The plunger was then moved in 1 mL increments from 10-20mL and volume and pressure were recorded, this was also done for 9mL, being recorded in 1 mL increments for 9mL to 5mL, and this step was repeated for three trials. The alcohol thermometer was then used to record room temperature with the syringe set to 3 mL, then adjusted to 10 mL, while the plunger is held in place for 15 seconds, this is also done when the syringe was set to 4 mL initially, and this step was repeated to create a volume range of 3-25 mL. The GoDirect Pressure Sensor kit with the 2 stoppers were then obtained, the room temperature was recorded and the blue tapered valve connector was used to connect the rubber stopper holes, vaccum grease was placed at the bottom of the thermometer and inserted into the one of the holes on the stopper, then a place of clear tubing connected the blue tapered valve connector and the gas pressure sensor, the flask with the sensor was placed half way into the larger flask of hot water from before for these recordings until the temperature reached 85C, then it was removed and pressure is recorded once the temperature reaches 80C for three trials and then the waste was properly disposed of and cleaned up.

How can we relate today's experiment and the chemical concepts with the kinetic molecular model?

Today's experiment and the chemical concepts with the kinetic molecular model can be related by looking at the relationship to Kelvin. This was seen in the measurement of Kelvin being included in the universal gas constant. Also, the ideal that gases are in constant motion. In relation to moles, if the number of moles increases this provides an increase in opportunity for the gas to collide with the walls of the container at any time. This chemical concept of the kinetic molecular model helps to back up the experimentally determined relationship between moles and pressure.

For one of your trials, show the calculation of the gas constant from the pressure and amount of gas data

𝑃𝑉 = 𝑛𝑅𝑇 Trial 1:(234311E3 Pa)(0.010L)/296.1K =7913 L*Pa/K*mol

For one of your trials, calculate the number of moles of air sealed in your SYRINGE. Show your work.

𝑚𝑜𝑙𝑒𝑠 = 𝐷𝑒𝑛𝑠𝑖𝑡𝑦∗𝑉𝑜𝑙𝑢𝑚𝑒 𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠 Trial 1: (0.001185 g/mL *11mL)/28.96 g =0.0004501 moles