Molecule size of water and oxygen

In summary, the conversation discusses the size of water and oxygen molecules and the possibility of finding a material to separate these two molecules through osmosis. The density and molecular weights of water and oxygen are mentioned, and it is determined that the volume of an oxygen molecule is approximately 1.56 times that of a water molecule. However, the approach of calculating the sizes of the molecules may not be effective due to their different geometrical shapes and the fuzzy boundaries of atoms and molecules. The suggestion is made to seek help in chemistry forums for finding a permeable membrane with the right chemical properties to achieve the desired separation.
  • #1
Coda
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0
Which size of the molecule is bigger? Water or oxygen?

Can someone state out the size unit of these molecules

And, can I find a meterial to separate this 2 matter but let one of it pass through the other? (Osmosis effect)

Really appreaciate who can help out here, thx
 
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  • #2
The density of water is 1kg/L and that of liquid oxygen is 1.14kg/L. The molecular weights are 18 and 32 respectively. So I reckon the volume of an oxygen molecule is about 32/(18*1.14)=1.56 times that of water. The exact volume of each molecule can be calculated using Avagadro's constant and the above data. If the molecules are assumed spherical, apply a factor of [tex] \frac{\pi}{3\sqrt 2} [/tex] for closely packed spheres and you can find out the radius.

Can't help with materials for osmosis.

Wai Wong
 
  • #3
I think to find the material for your osmosis purpose, calculating the 'sizes' of the molecules is not the right approach because they are of comparable volume but different geometrical shapes - oxygen molecule like a dumbbell and water molecule like a V shape. If a material have holes slightly bigger than an oxygen atom it should theoretically allow the passage of oxygen molecules but not water, but actually very few oxygen molecules are aligned in the right direction to get through. Also atom and molecules have fuzzy boundaries and the electron cloud of oxygen/water molecules will interact with that of the material around the hole, making passage difficult. If some or all holes are any larger, both molecules can get through. So a traditional approach of finding the membrane material may not work.

I suspect permeable membrane with certain chemical properties (e.g. hydrophobic) may do the trick. You may want to seek help in chemistry forums.

Wai Wong
 
  • #4
Hey, thanks for your reply.
It really helps a lot :)
 

1. What is the molecular size of water?

The molecular size of water is approximately 2.75 angstroms in diameter. This is equivalent to 0.275 nanometers or 0.000275 micrometers.

2. How does the molecular size of water affect its properties?

The small size of water molecules allows them to easily form hydrogen bonds with other water molecules, giving water its unique properties such as high surface tension, cohesion, and adhesion.

3. What about the molecular size of oxygen?

The molecular size of oxygen is approximately 3.46 angstroms in diameter. This is slightly larger than water molecules and allows for oxygen to diffuse and dissolve in water.

4. How does the molecular size of oxygen contribute to its role in respiration?

The small size of oxygen molecules allows them to easily diffuse through cell membranes and into cells, where it participates in cellular respiration to produce energy.

5. Can the molecular size of water and oxygen be changed?

No, the molecular size of water and oxygen is determined by the number and arrangement of atoms in their molecules, which cannot be changed without altering their chemical identities. However, their properties can be affected by external factors such as temperature and pressure.

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