CHEM 120 Lecture Notes - Lecture 3: Hot Air Balloon, Ideal Gas Law, Ideal Gas

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CHEM 120: Applications of the Ideal Gas Equation

Molar Mass of a Gas:

- You can rewrite the ideal gas law in terms of (m) mass of gas present and molecular

weight (M) rather than # of moles

o n = m/M

o PV= mRT/M → M = mRT/PV → m = MPV/RT

Gas Density: dependence on T & P

- d = m/V = MP/RT

o ONLY DEPENDS LINEARLY ON THE MOLECULAR WEIGHT AND THE SAME T & P

CONDITIONS

o Double the P, double the density

o Double the T, half the density

Fun Fact: ***Pressure of the gas outside of a hot air balloon is approx. ~ the same as the

pressure inside the balloon*** (due to the hole on the top of the balloon)

Archimedes; a body fully immersed in a fluid is buoyed upwards by a force equal to the weight

of the displaced fluid (e.g. hot air balloons work this way)

o Fbuoyant = mair g

o E.g. The hot air will move upward when the net upward force (buoyant) will be

greater than the mass of the air inside the balloon

▪ By calculating  you can do Fd = mball g

▪ F =  = (0.311)(9.8) = 0.003 N/L

The atmospheric fluid is much larger than the density of H2 (e.g. zeppelin) making the buoyant

force large

4.4 - Gases in Chemical Reactions:

- Gases react in volumes proportional to small whole numbers (Gay-Lussas’ La 88

o Volumes are proportional to coefficients in chemical equations

o V   Aogadro’s La

- Volume units; at constant P&T 0.68 L of O2 reacting with 1.36 H2 will produce 1.36 L H2O

(double the amount of H2 than O)

SLIDE FOR TNT QUESTIONS

Dalto’s La of Partial Pressures:

The total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of

each individual component in a gas mixture

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CHEM 120 Full Course Notes

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Chem 120: applications of the ideal gas equation. You can rewrite the ideal gas law in terms of (m) mass of gas present and molecular weight (m) rather than # of moles: n = m/m, pv= mrt/m m = mrt/pv m = mpv/rt. D = m/v = mp/rt: only depends linearly on the molecular weight and the same t & p. Conditions: double the p, double the density, double the t, half the density. Fun fact: ***pressure of the gas outside of a hot air balloon is approx. ~ the same as the pressure inside the balloon*** (due to the hole on the top of the balloon) Archimedes; a body fully immersed in a fluid is buoyed upwards by a force equal to the weight of the displaced fluid (e. g. hot air balloons work this way: fbuoyant = mair g, e. g. The atmospheric fluid is much larger than the density of h2 (e. g. zeppelin) making the buoyant force large.

Related Questions

What would be the independent, dependent, and controlled(need 3 controlled variable) variables in this lab?

- what would be a good hypothesis?

- for the second reaction, my teacher told us to change something in the lab and see how much gas forms after that, what would be something that we should change?

lb this lab we will be using our knowindge of stoicbiometry as well s the ideal gas law to calculate the amount of gas foemed in a chemical around-the-world balloos fights, they need to it is best for them to make these calculations before the flight rather during a chemical reaction. From this value, you can determine nation wen us the pere ent error. The ideal gas law can be used for many things For exampie, when hor air balloonists attempt caiculate how much gas they will have in thelr balloons at any time. Depending on the weight of than abruptly find out whilehalfway of the Indian Occan. During this lab, you will be determining the actual and peroent error of the reaction 1) Weigh out approximastely 5.0 g of NaHCO, (aka baking soda) on the balance. Record the exact amount of NaHCOs you 3) Pour the NaHCO, into a large deflated balloon using the plastic funnel When all of it 4) Very carefully place the balloon over the mouth of the flask, making sure that the meesured Pour 150 ml of IM HCI into a 250 ml Erlenmeyer flask make sure that all of it is in the main part of the balloon and none is in the opening has been added, tap the side of the balloon to NaHCO, does not fall into the flask. You may need pinches off the neck of the balloon to t0 to have one person stretching the mouth of the bailoon over the mouth of the flask while asodser p keep the powder from coming out Make sure that you're careful while doing this, because it will be easy for you t some of the acd on yourser while doing this. Wear safety goggles during this part of the lab, and if you splash acid on yourselt, make sure you wash it off with plenty of water 5) Once the balloon has placed over the mouth of the flask, have one person held it on so that it cannot fall off Once that person is ready and balloon is firmly fassened, another person should release all of the powder from the balloon inso the bydrochlonc lask You will immediately observe the forma on of bubbles a dor f an while the balloon inflates, the person holingä¼½ al should make sure that none of the gas escapes acid in the the balloon 6) When the reaction has stopped, take the balloon off the flask and tie off the end so it is closed. With a paper towel wipe off amy liqud which has splashed up into the nozzle oft eballon; this is very likely acadic, so make sure to wash your hands after touch ng 7 With a string and a ruler, find the circumference of the balloon in centimeters 8) Pour the solution into the waste container. Rinse flask 9) Repeat steps 1-8, but alter one variable Hypothesis As the pressure of Variables Independent-pressure h Dependent the amount of gas Cco) 3 Controlled-temperatureÂ·amount of HC, amoun4 of NaHCO3 Data: Table- Mea suremets for Baking Soda+ HCl Reaction Reaction 1 Reaction 2 Mass of sodium hydrogen carbonate ( Volume of hydrochloric acid ( Circumference of balloon( Barometric Pressure ( Temperature of Gas (

I need help writing a decent conclusion. Every time I submit a lab report the professor slams my conclusion saying it needs work. She wants us to state what the results mean and if they are as expected and explain the possible reasons for variation in your results. The lab is below with data/results. Please, please help.

The Ideal Gas Equation: The Determination of Gas Constant, R

Introduction:

The purpose of this experiment is to determine the gas constant R and the percentage of KClO₃ in the KClO₃ â KCl â MnO₂ mixture using the moles of O₂, the original weight of the mixture, and the stoichiometry of the reaction. Consider a plot PV vs. nT for a gas sample where P is the pressure of the gas, V is the volume occupied by the gas, n is the number of moles of gas, and T is the temperature of the gas in Kelvin. If the temperatures and pressures fall in normal ranges, the plot will yield a straight line. Thus, PV = nRT where R is the constant of proportionality between the PV product and the nT product. The object of this experiment is to determine P, V, n, and T for a gas sample and determine the gas constant R, using the equation PV = nRT. The gas sample used will be a sample of oxygen gas generated by the MnO₂ catalyzed decomposition of KClO₃. Following is the equation of the reaction:

For decomposition of the KClO₃ in a KClO₃ â KCl â MnO₂ mixture, the mass of O₂can be determined by taking the difference between the mass of the original mixture and the mass of the residue after the decomposition. This mass is then converted to moles of O₂ using the molecular weight of oxygen. The volume of the sample will be determined by water displacement in such a way that the pressure of the sample can be determined from the barometric pressure and the vapor pressure of water. The temperature of the sample will be directly measured.

Procedure:

Assemble the equipment for the apparatus shown in figure 1. With the Florence flask filled to the neck with water, the beaker one-third filled with water, and the pinch clamp open, blow into the tube which connects to the test to create a siphon between the flask and the beaker. Reverse the siphon a few times by raising and lowering the beaker. This will fill the tube connecting the flask and the beaker with water and will also remove air bubbles from the system. Adjust the siphon such that the flask is filled to the neck with water, and close the pinch clamp.

Weigh the eight inch test tube. Add approx. 1.5 grams of the KClO₃ â KCl â MnO₂mixture to the test tube and weigh the test tube containing the mixture. Record each weight to three decimal places. (Also, be sure and record the sample number for the KClO₃ â KCl â MnO₂.)

Clamp the test tube to the ring stand, and insert the stopper as shown in figure 1. With the pinch clamp open, raise the level of the beaker such that the water level in the beaker is several inches above the water level in the flask. If a significant amount of water runs into the flask, there is an air leak in the system. If you have an air leak, it must be closed before proceeding. Equalize the pressure in the flask with atmospheric pressure by bringing the water level in the beaker to the same height as the water level in the flask. After closing the pinch clamp, empty and dry the beaker. Open the pinch clamp. A small amount of water will run into the beaker: this will not affect your results since later in this experiment, you will again equalize the pressure in the flask with atmospheric pressure. Ask your instructor to check your apparatus before proceeding.

Heat the mixture with a blue flame until the mixture first begins to melt and then solidifies again; and then heat for an additional 2 mins. (Donât heat more than 7 mins.) Allow the system to cool for 15 mins. Equalize the pressure with atmospheric pressure, as before; then close the pinch clamp and open the system. Quickly measure the temperature of the gas in the flask; also measure the volume of water in the beaker. Record the barometric pressure reading from professor. Weigh the test tube with the residue and record the mass to three decimal places.

Data/Results:

	Trial 1
Weight of test tube	41.912 g
Weight of test tube + mixture	43.343 g
Weight of mixture	1.431 g
Weight of test tube + residue	43.211 g
Weight of oxygen	0.132 g
Moles of oxygen	0.00413 mol
Temperature of water (under oxygen)	21.0 ⁰C
Temperature of oxygen	20.5 ⁰C
Barometric pressure	761.5 torr
Vapor pressure of water	18.7 torr
Pressure of oxygen	742.8 torr
Volume of water displaced	0.101 L
Gas constant, R	61.9
Mass of KClO₃ in mixture (use balanced equation)	0.338 g
% of KCLO₃ in mixture	23.6 %

CHEM 120 Lecture Notes - Lecture 3: Hot Air Balloon, Ideal Gas Law, Ideal Gas

CHEM 120 Full Course Notes

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