Oxygen momentum

[COYspurs]

In a bottle, hydrogen will have a greater velocity than oxygen, but will oxygen travel with a greater momentum?

Thanks.

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[Isoprop]

Let's see.

In a bottle, hydrogen gas and oxygen gas molecules should have the same average kinetic energy (KE)

where p = momentum, m = mass of a gas molecule, and v = (rms) velocity.

Since the average kinetic energies should be equal for H and O:

the sub O's and H's stand for oxygen and hydrogen.

The 2's cancel out.

Also, oxygen gas has a mass of 32 amu. Hydrogen gas has a mass of 2 amu. Thus,

The momentum of oxygen gas is on average 1/4 of that of hydrogen gas (if my calculations are correct).

 

[loveoforganic]

Shouldn' it be 4pH by your last step?

It's my understanding heavier gas molecules always carry more momentum at equal kinetic energy.

 

[premed101]

Let's see.

In a bottle, hydrogen gas and oxygen gas molecules should have the same average kinetic energy (KE)

where p = momentum, m = mass of a gas molecule, and v = (rms) velocity.

Since the average kinetic energies should be equal for H and O:

the sub O's and H's stand for oxygen and hydrogen.

The 2's cancel out.

Also, oxygen gas has a mass of 32 amu. Hydrogen gas has a mass of 2 amu. Thus,

The momentum of oxygen gas is on average 1/4 of that of hydrogen gas (if my calculations are correct).

I think he meant the momentum of Hydrogen is 1/4 the momentum of oxygen

 

[COYspurs]

Cool, that's what I thought...hydrogen has greater velocity, but oxygen has more momentum.

Appreciate it.

 

[Isoprop]

yeah my math was off in the last step using latex. switch em around.

 

[wanderer]

Shouldn' it be 4pH by your last step?

It's my understanding heavier gas molecules always carry more momentum at equal kinetic energy.

Yes.


There is no need for long calculations. Just keep in mind that p = 2* Ke/ v
Since gases at same temperature always have same Ke, the gas with the lower velocity will have higher momentum; thus the heavier gas has more momentum.