Question

Help please What mass, in grams, of oxygen gas (O2) is contained in a 8.5 liter tank at 32.0 degrees Celsius and 3.23 atmosphere?

Answer 1

@dan815 @aaronq @Luigi0210

Answer 2

Use pV= mRT/Mr, where in is in Pascals, V in m^3, R is 8.31, T is temperature in Kelvin , m is required mass and Mr is molecular mass. Think you can solve it now?

Answer 3

yea i got that part but i need to know the steps

Answer 4

Make sure you're using the proper gas constant. I would use 0.0821 instead since you're already given liters and atm.
Just convert temperature to absolute temp (which is kelvin)

Answer 5

this is what i got so far (3.23 atm)(8.5l)=(n)(0.082atm*L/mole*K)(274.15k)

Answer 6

and im stuck @thadyoung @Hoslos

Answer 7

You need to rearrange like you would in algebra, and solve for \(n\)
which is moles
then you can use that to calculate grams.
Since you know that oxygen has a molar mass of 16, which is given in grams per mole

Answer 8

Rearrange: \(\sf PV = nRT \Rightarrow \color{red}{\frac{PV}{RT}}= n\)

Answer 9

okay so
(3.23)(8.5L)/(0.082atm*L/mole*K)(274.15)?

Answer 10

@thadyoung

Answer 11

Close, but where did you come up with 274.15 for your temperature?

Answer 12

i converted the celcius into kelvin

Answer 13

so 32.0C is 274.15 K

Answer 14

32 degree's celcius is \(not\) 274.15 K
Do you know the conversion?

Answer 15

no

Answer 16

its 305.15 @thadyoung

Answer 17

so its 3.23 atm x 8.5L / (0.08206 Latm/molK x305K)

Answer 18

am i correct?

Answer 19

Yes.

Answer 20

now whats next?

Answer 21

this is where i get stuck

Answer 22

Well, you have moles.
Remember from algebra, if you have this: \(\sf \large \frac{a}{b} \times \frac{b}{z} = \frac{a}{z} \)
because the two b's cancel out? \(\sf \large \frac{a}{\cancel{b}} \times \frac{\cancel{b}}{z} = \frac{a}{z} \)

Answer 23

yes

Answer 24

It is the same thing with units.
You have moles of Oxygen (O\(_2\))

And when you see your periodic table, you know that the units are in molar mass.
Which menas you have

n moles of O\(_2\) \(\times\) \(\sf \frac{15.99~g}{mol}\)

Answer 25

That's the mass for oxygen.

Answer 26

Now, does that make sense?

Answer 27

ohh k yea kind of

Answer 28

Notice that you have units mole that can cancel out?

Answer 29

This is still simple algebra.

Answer 30

yes

Answer 31

so the two moles cancel out?

Answer 32

Yes.

Answer 33

so how would the formula look now

Answer 34

exactly how i wrote it up there. try it.

Answer 35

okay so one mole of ox weighs 32g so i multiply that by what 15.99g?

Answer 36

@thadyoung

Answer 37

im so confused? :(

Answer 38

whats ar ethe number of moles?

Answer 39

Put it in your calculator! I'm not doing your work for you.
I already showed you how to do it.