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### Topic: How much Lt Oxygen in water  (Read 1513 times)

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#### 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...

#### 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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#### Helly

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

#### 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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#### 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?

#### 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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#### 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 ?

#### Borek

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##### Re: How much Lt Oxygen in water
« Reply #7 on: February 07, 2020, 04:23:01 PM »
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#### 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 ?

#### 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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#### Helly

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

#### 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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#### 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?

#### 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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#### 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.