AvLaw - Which is the correct method of finding moles of gases?

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Discussion Overview

The discussion revolves around the calculation of moles of methane gas (CH4) in a 1000 L steel storage tank, based on Avogadro's law. Participants explore different methods of calculating moles, considering factors such as temperature and pressure, and the implications of using standard conditions.

Discussion Character

  • Homework-related
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant calculates moles using mass and molar mass, yielding 5517.4 moles, and another method using volume at standard temperature and pressure (STP), yielding 44.6 moles.
  • Some participants note that the 22.4 L per mole applies only at STP and emphasize that the gas is likely under pressure, which affects the calculation.
  • There is uncertainty about the correct number of moles due to unspecified temperature conditions, with some suggesting that the first calculation is valid regardless of temperature.
  • Others propose that knowing the temperature would allow for pressure calculations, indicating that the gas is likely highly pressurized unless at low temperatures.
  • One participant expresses confusion about their initial calculation and receives encouragement to revise their understanding of the concepts involved.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct method for calculating moles, as there are competing views regarding the impact of temperature and pressure on the calculations.

Contextual Notes

The discussion highlights limitations related to unspecified temperature and pressure conditions, which affect the validity of the calculations presented.

axer
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Homework Statement


Based on your understanding of Avogadro's law.
1000 L steel storage tank contains 88.5 kg of methane gas, CH4.
Calculate no. of moles.

The Attempt at a Solution


one method= no. of moles=mass/molar mass.
no. of moles= 88500/16.04= 5517.4 moles.other method= 1 mol= 22.4 liter.
no of moles= 1000 L/22.4L= 44.6 moles.

Please inform me of the correct method, thanks!
 
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The 22.4 L for one mole is only at S.T.P.=Standard temperature and pressure. They did not specify the temperature, but the much bigger factor here is the gas in the container is undoubtedly pressured. Assuming it is at standard temperature (zero degrees Centigrade), you could compute the pressure in atmospheres by taking the ratio of your first answer divided by your second (incorrect answer).
 
Charles Link said:
The 22.4 L for one mole is only at S.T.P.=Standard temperature and pressure. They did not specify the temperature, but the much bigger factor here is the gas in the container is undoubtedly pressured. Assuming it is at standard temperature (zero degrees Centigrade), you could compute the pressure in atmospheres by taking the ratio of your first answer divided by your second (incorrect answer).
So 5517.4 moles is the correct number of moles? since they didn't specify the temp.
 
axer said:
So 5517.4 moles is the correct number of moles? since they didn't specify the temp.
Yes, it is correct, regardless of the temperature. Upon being given the temperature, it would also be possible to compute the pressure. You would find that the gas is highly pressurized, unless it is being kept at very low temperature.
 
Charles Link said:
Yes, it is correct, regardless of the temperature. Upon being given the temperature, it would also be possible to compute the pressure. You would find that the gas is highly pressurized, unless it is being kept at very low temperature.
Oh by using the ideal gas law, ok thanks!
 
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Your first answer was correct. How could you doubt it?
In this and other questions you have shown yourself to have some grasp but were easily distracted and confused by irrelevancies. Things that were related to a question but made you miss a point.
So having been partially successful and activated it is a good time, I recommend, to go back and do some revision in order to get the concepts fixed securely in your mind. :smile:
 
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