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Topic: How much Lt Oxygen in water  (Read 1052 times)

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Offline Helly

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How much Lt Oxygen in water
« on: February 06, 2020, 02:05:43 AM »
the solubility of oxygen in 1 lt water 25 c 1 atm is 28 ml. How much Lt O2 can be dissolve in 1 lt water 25 c 4 atm?

I though using PV=nRT which gives me PV=P2V2, V2 = 7ml.
I dont understand Henry Law...

Offline Borek

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Re: How much Lt Oxygen in water
« Reply #1 on: February 06, 2020, 03:59:02 AM »
You can't use some randomly selected law to solve a problem that is described by another one. It won't ever work. But you are right mentioning Henry's Law, that's the one that should be used here.

Can you write the Henry's law? What does it say?
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Offline Helly

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Re: How much Lt Oxygen in water
« Reply #2 on: February 06, 2020, 01:34:12 PM »

Offline Borek

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Re: How much Lt Oxygen in water
« Reply #3 on: February 06, 2020, 03:28:18 PM »
Sadly, wikipedia article is poorly written, no wonder you feel lost.

See if this formulation won't be better.
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Offline Helly

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Re: How much Lt Oxygen in water
« Reply #4 on: February 07, 2020, 09:36:06 AM »
C = k.P
C = Molarity
k = Henrys Law
P = Pressure

So, how i should find C?

Offline Borek

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Re: How much Lt Oxygen in water
« Reply #5 on: February 07, 2020, 10:41:55 AM »
the solubility of oxygen in 1 lt water 25 c 1 atm is 28 ml

You know how much oxygen dissolved and in what volume.
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Offline Helly

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Re: How much Lt Oxygen in water
« Reply #6 on: February 07, 2020, 01:30:10 PM »
Ok. So, the molarity is n/volume

While the mole of oxygen using pv/RT=n ? = 28/(0.082 * 298) = n ?

Offline Borek

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Re: How much Lt Oxygen in water
« Reply #7 on: February 07, 2020, 04:23:01 PM »
Close, but watch your units.
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Offline Helly

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Re: How much Lt Oxygen in water
« Reply #8 on: February 08, 2020, 10:33:44 AM »
0.028/(0.082 * 298) = mole

Then i get C


 should i find k? Or P ?

Offline Borek

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Re: How much Lt Oxygen in water
« Reply #9 on: February 08, 2020, 02:17:42 PM »
Pressure is given, find k, then calculating amount of oxygen dissolved at any other pressure will be trivial.
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Offline Helly

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Re: How much Lt Oxygen in water
« Reply #10 on: February 08, 2020, 02:59:39 PM »
Ok thanks

Offline Borek

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Re: How much Lt Oxygen in water
« Reply #11 on: February 08, 2020, 03:56:18 PM »
Note: there are many ways to skin that cat. Actually once you understand the Henry's law and direct proportionality the answer is immediately obvious. I preferred to show you the most sure way, which may be not the fastest, but is guaranteed to yield a correct result.
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Offline Helly

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Re: How much Lt Oxygen in water
« Reply #12 on: February 09, 2020, 08:22:55 AM »
What is that?

Offline Borek

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Re: How much Lt Oxygen in water
« Reply #13 on: February 09, 2020, 05:01:21 PM »
One of possible formulations of Henry's law is that no matter what the pressure is, the volume of the gas that dissolves in a given volume of liquid is always the same.
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Offline Enthalpy

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Re: How much Lt Oxygen in water
« Reply #14 on: February 10, 2020, 10:14:42 AM »
the solubility of oxygen in 1 lt water 25 c 1 atm is 28 ml. How much Lt O2 can be dissolve in 1 lt water 25 c 4 atm?

I should like to recommend writing the units properly, too, including capital letters.
Litre is L
Degree celsius is °C
and so on and so forth. It's not only easier to read if you follow the habits, it does also make a difference. Readers understand K as kelvin and k as thousand, M as mega and m as milli. Even without readers, you'll fool yourself if you mix up the symbols.

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