Calculating the total and partial pressure of gas mixture

In summary, the problem involves a 1 L flask containing 1 mole of O2 and an unknown amount of N2 gas at a pressure of 5 atm and a temperature of 10 degrees Celsius. Using the ideal gas law and calculations, it is determined that there is actually 1.2153 moles of total gas in the system. The problem asks what the total pressure would be after 2 moles of gas are allowed to escape. However, since there is not even 2 moles of gas in the system, it is impossible for 2 moles to escape. The resulting values for total pressure and partial pressure of O2 make sense, but it is unclear how 2 moles can escape when there is
  • #1
Lester_01
2
0
1. The problem/question is as follows:

1 mole of O2 mixed with N2 gas (PN2= 5 atm at 10 degrees celcius in a 1 L flask. What is the total pressure after 2 moles of gas is allowed to escape? How about the partial pressure of O2?

[tex]R= 0.08206\frac{L atm}{mol K}[/tex]

Homework Equations


Using the ideal gas law, I have calculated the quantity of moles of nitrogen gas in the mixture, I add one mol of oxygen and it results in 1.2153 moles total. The problem states that 2 moles of gas are allowed to escape, yet there is not even 2 moles of gas in the system. We can't have negative moles so the situation seems impossible, or a poorly designed question at best.

The Attempt at a Solution



Ptot= ∑PO2 + PN2

nN2=[tex]\frac{PV}{RT}[/tex]

= [tex]\frac{(5)(1)}{(0.08206)(283)}[/tex]

= 0.2153 moles N2

ntot = 1 + 0.2153 = 1.2153 moles total

PN2= Ptot [tex]/frac{nN2}{ntot}[/tex]

[tex]5= Ptot\frac{0.2153}{1.2153}[/tex]

[tex]\frac{5}{0.1772}[/tex]= Ptot= 28.22 atm

PO2= 23.22 atmThese values seem to make sense, but I'm not sure how to reconcile for how 2 moles are escaping.

Interestingly, if I subtract 2 moles from the 1.2153 and in corporate that into the procedure as ntot, it will result in a negative total pressure of -18 atm, and also interestingly result in PO2= -23.22 atm (the opposite of the result above)


Any information regarding how 2 moles can escape out when there is only 1.2153 moles contained?

PS Sorry about the coding, it for some reason isn't working very well.
 
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  • #2
Or I'm thinking the answer could simply be zero for both cases because all particles of gas have escaped, all the moles are gone and there's no pressure in the flask in that case.
 

Related to Calculating the total and partial pressure of gas mixture

1. How do you calculate the total pressure of a gas mixture?

The total pressure of a gas mixture can be calculated by adding together the partial pressures of each individual gas component. This can be done using the ideal gas law, Ptotal = ntotalRT/V, where ntotal is the total number of moles of gas, R is the ideal gas constant, T is the temperature in Kelvin, and V is the volume of the gas mixture.

2. What is partial pressure and how is it calculated?

Partial pressure refers to the pressure exerted by a single gas component in a mixture. It is calculated by multiplying the mole fraction of the gas by the total pressure of the mixture. This can also be expressed as Ppartial = npartialRT/V, where npartial is the number of moles of the specific gas component.

3. How do you determine the mole fraction of a gas in a mixture?

The mole fraction of a gas can be calculated by dividing the number of moles of that gas by the total number of moles in the mixture. This can also be expressed as X = npartial/ntotal.

4. Can the total pressure of a gas mixture change?

Yes, the total pressure of a gas mixture can change if there is a change in the number of moles of gas, temperature, or volume. According to the ideal gas law, Ptotal is directly proportional to the number of moles of gas and temperature, and inversely proportional to the volume.

5. How does the presence of non-ideal gases affect the calculation of total and partial pressure?

The ideal gas law assumes that gases behave ideally, meaning they have no intermolecular forces and occupy no volume. However, in reality, most gases deviate from this behavior. Non-ideal gases can affect the calculation of total and partial pressure by causing errors in the predicted values. In these cases, more complex equations, such as the van der Waals equation, may need to be used to account for the non-ideal behavior of gases.

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