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

AI Thread Summary
The correct method for calculating the number of moles of methane gas in a 1000 L steel storage tank is to use the formula for moles, which is mass divided by molar mass, resulting in 5517.4 moles. The alternative method using the volume of gas at standard temperature and pressure (STP) yields an incorrect result of 44.6 moles, as this value only applies under specific conditions. The discussion emphasizes that the temperature was not specified, but the gas is likely under pressure, affecting the calculation. It is confirmed that the first calculation is accurate regardless of temperature, and the ideal gas law can further clarify the situation if temperature data were provided. Overall, understanding the principles of gas behavior is crucial for accurate calculations in chemistry.
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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