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# why do equal volumes have an equal number of molecules watch

1. why do equal volumes have an equal number of molecules?
2. (Original post by celina10)
why do equal volumes have an equal number of molecules?
This is only true within the perfect gas law. Just plug in the numbers and you get the ~24dm3/mol
3. (Original post by JMaydom)
This is only true within the perfect gas law. Just plug in the numbers and you get the ~24dm3/mol
But then why is it accepted to be true? What's the idea behind it? I don't understand it, if a molecule is heavier wouldn't it be more attracted to the earth and then the molecules would be more packed together as they would have less space that they can possibly occupy? Or the difference in mass so small it's accepted to be negligible?
4. (Original post by celina10)
But then why is it accepted to be true? What's the idea behind it? I don't understand it, if a molecule is heavier wouldn't it be more attracted to the earth and then the molecules would be more packed together as they would have less space that they can possibly occupy? Or the difference in mass so small it's accepted to be negligible?
I think you're right. In a perfct gas, each molecule is very far away from every other molecule and only a tiny percentage of the volume of the gas is actual 'stuff' so the difference in space is negligable even when you're comparing large and small molecules.
5. (Original post by celina10)
But then why is it accepted to be true? What's the idea behind it? I don't understand it, if a molecule is heavier wouldn't it be more attracted to the earth and then the molecules would be more packed together as they would have less space that they can possibly occupy? Or the difference in mass so small it's accepted to be negligible?
More attracted to earth??? , not really for something as tiny as a gas molecule.

The reason for this is because in a gas, most of its volume is the empty space between the molecules. The molecules themselves are so tiny and so far apart that they contribute almost nothing to the total volume at standard conditions, making it ~24dm3
6. (Original post by LeonVII)
More attracted to earth??? , not really for something as tiny as a gas molecule.

The reason for this is because in a gas, most of its volume is the empty space between the molecules. The molecules themselves are so tiny and so far apart that they contribute almost nothing to the total volume at standard conditions, making it ~24dm3
Oh I understand now, I was referring to gravity but now that I thought about it properly what I was thinking before doesn't make sense. So as long as the temperature and pressure is the same, there would be 1 mol of a gas in 24 dm3.

How does temperature affect the volume one mol occupies? Do the particles have more kinetic energy so they mover further apart?
7. (Original post by celina10)
How does temperature affect the volume one mol occupies? Do the particles have more kinetic energy so they mover further apart?
Yep.
8. (Original post by celina10)
Oh I understand now, I was referring to gravity but now that I thought about it properly what I was thinking before doesn't make sense. So as long as the temperature and pressure is the same, there would be 1 mol of a gas in 24 dm3.

How does temperature affect the volume one mol occupies? Do the particles have more kinetic energy so they mover further apart?
No, they only occupy 24dm3 at 1 atm and 25 degrees, standard conditions.

A gas at -56 degrees and 1 atm would not occupy that amount.

And yes, the higher the temperature, the larger the volume and thus lower the pressure
9. This value comes from the perfect gas law, which is derived from considering an ideal gas. An ideal gas assumes that:

1. particles take up no volume
2. particles do not interact
3. random movement

Obviously this is not the case for all gases but it works to a reasonable approximation (and is exact at the boyle temperature)

So, the reason it is the same for all gases is because we are assuming that all gases are ideal (i.e. they are all the same). Real volumes per mole will be different from the ideal gas value as the real gases interact, have an excluded volume etc etc.
10. (Original post by celina10)
why do equal volumes have an equal number of molecules?
I dont know
11. (Original post by abdullah hayyan)
I dont know
and you commented because...?
12. (Original post by JMaydom)
This value comes from the perfect gas law, which is derived from considering an ideal gas. An ideal gas assumes that:

1. particles take up no volume
2. particles do not interact
3. random movement

Obviously this is not the case for all gases but it works to a reasonable approximation (and is exact at the boyle temperature)

So, the reason it is the same for all gases is because we are assuming that all gases are ideal (i.e. they are all the same). Real volumes per mole will be different from the ideal gas value as the real gases interact, have an excluded volume etc etc.
thank you
13. (Original post by celina10)
and you commented because...?
Because I like to

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