Justin WongChem 053-104

Ideal Gases

Purpose The purpose of this lab was to determine both quantitatively and qualitatively how various gases deviate from the Ideal Gas Law in their behavior.

Data and Results

ConstantsVolume of beaker: 0.13 LTemperature: 293 KelvinVolume of “airbag”: 0.75 LOne Molar HCl solution6 Molar CH3COOH solutionAmbient Pressure: 1.01 atmospheres

Theoretical ResultsIn both reactions that produced hydrogen gas, 0.3 atm is the expected change in pressure

Actual Results (Hydrogen gas production)Mg(s)+2HCL (aq)MgCl2(aq)+H2(g)

Trial 1: Pi=1.01 atm Pf=1.2246 atm P=0.21 atm Yield: 70%

Trial 2: Pi=1.01 atm Pf=1.277 atm P=0.26 atm Yield: 86.7%

2HCl(aq)+NaCO3(s)= 2NaCl(aq)+H2O(l)+CO2

Trial 1: Pi=1.01 atm Pf=1.275 atm P=0.265 atm Yield: 83.33%

Trial 2: Pi=1.01 atm Pf=1.279 atm P=0.269 atm Yield: 89.67%

*We omitted the trials when we were using a defective beaker that leaked. Pressure did not change as hydrogen gas was produced to the leak

Airbag Results

Na2CO3(s)+2CH3COOH(aq)2CH3COONa(aq)+H2O(l)+CO2(g)

3.339 grams of Na2CO3 was needed to theoretically inflate the airbag

We observed in the airbag reaction that the airbag inflated and became very full, but not as full as it could be. This is due to carbon dioxide not being an ideal gas. A milky white solution was also produced, and the bag became very warm

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Calculations Part 1Mg(s)+2HCL (aq)MgCl2(aq)+H2(g)

TheoreticalV=0.13 L T=298 K Pi=1.00 atm Pf=1.3 atmN=(PV)/(RT)=0.00159 moles of gas produced

0.00159 moles H2*(1 mol Mg/1 mol H2)=0.00159 moles Mg needed0.00159 moles H2*(2 mol HCl/1 mole H2)=0.00318 moles of HCl needed

n(theoretical)=0.00159 moles H2 Actual

n(actual)=((0.26 atm)(0.13L))/(0.0821*298 K)=0.00138 molespercent yield: 0.00138/0.00159=86.9%

Part 2

Na2CO3(s)+2CH3COOH(aq)=2CH3COONa(aq)+H2O(l)+CO2(g)

Theoretical

n=(PV)/(RT)=((1.01 atm)(0.75 l))/(0.0821 mol L*atm/mol*K)(293 K)=0.0315 moles of gas needed to fill the bag.

By molar proportions, 0.0315 moles of Na2CO3 would be needed as well, and 0.063 moles of CH3COOH would be needed

0.00315 moles Na2CO3=3.34 g needed

0.063 moles CH3COOH*(1 Liter/6 mol CH3COOH)=0.0105 L of CH3COOH needed.

Actual

3.339 g of Na2CO3 used, and excess acetic acid (0.015L)

Van der Waals correction shown below

Van der Waals Calculations

Discussion

1. Although we should expect to see that both reactions yield a pressure of 0.3 atm, the pressure produced by the reaction with sodium carbonate was higher than the pressure produced by the reaction where magnesium was used. The yield for the experiment where sodium carbonate was used was also much higher. With magnesium, the average yield over the two trials was 78.35%. The average yield where sodium carbonate was used was 86.5%. This indicates that either higher proportion of sodium carbonate reacted, or that the carbon dioxide produced

2. One source of error could be the reactions not going to completion before pressure readings were recorded. After we recorded our final pressures, we noticed that the pressure continued to rise, albeit slowly. This would result in a recorded pressure that was lower than the true pressure after the reaction went to completion. This might account for the low yields.

3. The yield in the sodium carbonate reaction where carbon dioxide was produced was much higher than the yield in the magnesium reaction where hydrogen was produced. This is due to the size of the carbon dioxide molecules. Since carbon dioxide molecules take up more space than hydrogen molecules, the effective volume of the rigid container is smaller when it is filled with carbon dioxide than when it is filled with hydrogen. The smaller volume available in the beaker filled with carbon dioxide gas translates to a higher observed pressure, and a higher observed yield.

Post Lab Questions1. 0.0315 moles were needed to theoretically fill up the airbag2. The bag did not inflate fully since the carbon dioxide produced by the reaction is not an

ideal gas. In real gases, the particles that make up the gas attract each other when they get close enough to each other. Since they attract each other, they bump into the wall of a container less often than in an ideal gas, where collisions between particles are not accounted for. Since they bump into the sides of the container less often than in an ideal gas, the airbag is not inflated fully, and more gas particles must be added to correct for this in order to fill the bag completely.

3. The moles of CO2 required to fill the bag according to the Van der Waals correction is 0.3164. This is a 0.4% increase in the number of moles required.