Gas density problem!

[virtualmaster999]

Hey everyone, quick question on gas density (not sure if it comes up a lot by the way)

p= 380 torr
v=44.8L
t=10*C (283K)
mass= 20 g

What is the density?
So I know you can use either d=m/v or d= p*mm/RT

Can you do 20/44.8? And if you use the second equation, what is the easiest way to find n, so you can get molar mass?

Thanks in advance!

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[DAT Destroyer]

Hey everyone, quick question on gas density (not sure if it comes up a lot by the way)

p= 380 torr
v=44.8L
t=10*C (283K)
mass= 20 g

What is the density?
So I know you can use either d=m/v or d= p*mm/RT

Can you do 20/44.8? And if you use the second equation, what is the easiest way to find n, so you can get molar mass?

Thanks in advance!

Your Density question is fantastic ! Gas volumes are affected by temperature and pressure, hence the density of a gas is changed by these conditions. Gases become less dense with increasing temperature,,,,,Gases also become more dense as pressure rises..... To calculate the density of a gas at Conditions OTHER THAN STP......use the derived equation P ( MW ) = DRT..... If you are at STP....1atm and 273K.....then your method using d = m/v would work.

I hope this clears this often baffling concept up for you.

Dr. Romano

 

[virtualmaster999]

Your Density question is fantastic ! Gas volumes are affected by temperature and pressure, hence the density of a gas is changed by these conditions. Gases become less dense with increasing temperature,,,,,Gases also become more dense as pressure rises..... To calculate the density of a gas at Conditions OTHER THAN STP......use the derived equation P ( MW ) = DRT..... If you are at STP....1atm and 273K.....then your method using d = m/v would work.

I hope this clears this often baffling concept up for you.

Dr. Romano

That makes more sense. So in this case, since you're not at stp, you need to find the number of moles so you can obtain molar mass, which is the only unknown right? How would you go about solving for the number of moles when you're not at stp?


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[virtualmaster999]

Your Density question is fantastic ! Gas volumes are affected by temperature and pressure, hence the density of a gas is changed by these conditions. Gases become less dense with increasing temperature,,,,,Gases also become more dense as pressure rises..... To calculate the density of a gas at Conditions OTHER THAN STP......use the derived equation P ( MW ) = DRT..... If you are at STP....1atm and 273K.....then your method using d = m/v would work.

I hope this clears this often baffling concept up for you.

Dr. Romano

And also, if you were at stp for this specific problem, would you do 20g/44.8L? I'm just unsure of how to do the calculation now to get the answer.


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[DAT Destroyer]

The best way to find number of moles of a gas is to use the ideal gas law equation.

Try this and see if it helps.

 

[virtualmaster999]

The best way to find number of moles of a gas is to use the ideal gas law equation.

Try this and see if it helps.

Hmm ok. So would I be able to do 20g/44.8 L in this case, or would it be necessary for me to use the other formula by solving for molar mass?


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[DAT Destroyer]

Hmm ok. So would I be able to do 20g/44.8 L in this case, or would it be necessary for me to use the other formula by solving for molar mass?


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Solve for moles using PV = nrt.......once you get moles,,,,,,MW = g/mole.........once you get MW......then use P(MW)= DRT

 

[virtualmaster999]

Solve for moles using PV = nrt.......once you get moles,,,,,,MW = g/mole.........once you get MW......then use P(MW)= DRT

Thanks that makes sense! And just to make sure I got my bases covered: if this WAS at STP, then I could do 20g/44.8L right?


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[DAT Destroyer]

Thanks that makes sense! And just to make sure I got my bases covered: if this WAS at STP, then I could do 20g/44.8L right?


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Yes.....that is correct...Keep up the great work.....
Now do a few problems...... Another nice thing to remember is that 1 mole of ANY gas at STP occupies 22.4 liters !!!

Dr. Romano

 

[virtualmaster999]

Yes.....that is correct...Keep up the great work.....
Now do a few problems...... Another nice thing to remember is that 1 mole of ANY gas at STP occupies 22.4 liters !!!

Dr. Romano

Thanks for all the help Dr. Romano!


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[100%permwinner]

Just do 20/44.8! You can certainly rearrange the ideal gas equation to find n (PV/RT), MW (m/n), and density. Variables P, R, T will cancel out in the process.

 

[virtualmaster999]

Just do 20/44.8! You can certainly rearrange the ideal gas equation to find n (PV/RT), MW (m/n), and density. Variables P, R, T will cancel out in the process.

So either way you get the same answer?


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[100%permwinner]

Exactly. In the end, your answer should be 0.446 g/L. I think the extra info are there to distract/confuse you so try not to do more work than necessary.

 

[starsbeneathme]

what's the answer for this?