[omgwtfitsp]

Hey guys, I'm sorry for posting another question but this is my last one I need some with for my test on gas.

"The pressure exerted on a diver increases about 125 Kpa for every 10m of depth. A scuba diver uses air at a rate of 6L per minute at a depth of 10m where the pressure is 250 kPa (125 kPa due to atmosphere pressure and 125 kPa due to water pressure) and the temperature is about 14 degrees Celsius. If the diver's 15L air tank is filled to a pressure of 3.6 x 10^4 kPa (36 000 kPa) at a dockside temperature of 26 degrees Celsius, how long could the diver remain safely submerged?"

I was messing around with calculations using the Combined Gas Law but I got some crazy answer that did not seem correct to me at all. Maybe there is something wrong with the question or a typo with the numbers?

Please does anyone have any idea how to solve this? Give me some hints so I may try it? Cuz my chem teacher gives crazy questions on tests and sometimes he can't even answer his own questions! So dumb...

[cliverlong]

Hey guys, I'm sorry for posting another question but this is my last one I need some with for my test on gas.

<< snip >>

I was messing around with calculations using the Combined Gas Law but I got some crazy answer that did not seem correct to me at all. Maybe there is something wrong with the question or a typo with the numbers?

Please does anyone have any idea how to solve this? Give me some hints so I may try it? Cuz my chem teacher gives crazy questions on tests and sometimes he can't even answer his own questions! So dumb...

Please show your attempt and add note on why you think your answer is crazy.

Clive

[omgwtfitsp]

Hey guys, I'm sorry for posting another question but this is my last one I need some with for my test on gas.

<< snip >>

I was messing around with calculations using the Combined Gas Law but I got some crazy answer that did not seem correct to me at all. Maybe there is something wrong with the question or a typo with the numbers?

Please does anyone have any idea how to solve this? Give me some hints so I may try it? Cuz my chem teacher gives crazy questions on tests and sometimes he can't even answer his own questions! So dumb...

Please show your attempt and add note on why you think your answer is crazy.

Clive

Sure okay, well after messing around with this some more, I found another answer that at least could possibly make sense but i don't know if this is correct.

So here is how I listed my givens:

P2 = 250 kPa
T2 = 287 K
V2 = ?

V1 = 15.0 L
P1 = 3.6 x 10^4 kPa
T1 = 299 K

So using the combined gaw law, P1V1/T1 = P2V2/T2, I rearranged the formula to give me V2.

So it turned out to be V2 = P1V1T2/T1P2
After substituting the values in for formula, I got an answer of about 2073 L. So then I took that and divided it by 6L/min and got 345.5 minutes or 5.76 hours approx. Do you think this is a reasonable answer? I feel as though something is not right.

[cliverlong]

<< snip >>
So it turned out to be V2 = P1V1T2/T1P2
After substituting the values in for formula, I got an answer of about 2073 L. So then I took that and divided it by 6L/min and got 345.5 minutes or 5.76 hours approx. Do you think this is a reasonable answer? I feel as though something is not right.

Looks reasonable to me
Look at the numbers given and the values you calculated. The air in the tank is under high pressure and when it comes out (via the regulator) at the pressure of the surrounding water, it will occupy over 100 times more volume than when it is in the tank. So be able to deliver air for 5.76 hours seems fine to me.

The only question I have is the question is posed as "how long could the diver remain safely submerged?" and you have calculated how long the tank can deliver gas at the presure of the surrounding. If the emphasis is on safety I'm sure there are physiological limits to the time a diver should spend under water. I'm guessing the diver gets tired much more quickly than on land and that there would be some algorithm or formula that relates how long one spends breathing at pressure to how long should allow to come to the surface.

Clive

[Borek]

6L per minute looks way to low for me.

[cliverlong]

6L per minute looks way to low for me.

That may be a low value for the demand on air from the tank but it is the data given in the question.

Air demand will vary according to the activity, and anxiety of the diver.

[Borek]

I know it was given in the question. You have already questioned other aspect of the question validity, so I just added what was my first thought when I saw the question

[cliverlong]

I know it was given in the question. You have already questioned other aspect of the question validity, so I just added what was my first thought when I saw the question

Aha ! I'm on your wavelength now ! TBH , I have no idea what is a "reasonable" value for the rate of breathing at rest.

[Borek]

I seem to remember that about 8L per minute could do, but only when sleeping in warm water