Solubility of gases at different temperatures

[gwiyomi17]

I search on the internet about how does temperature affect the solubility of gases then I found two different answers:

 

An increase in temperature results in a decrease in gas solubility in water, while a decrease in temperature results in an increase of gas solubility in water.

The other one was vice versa of this statement.

 

Which is correct between different ideas that I searched? I think the first is correct but I don't know how to explain it.

Based on what I understand, since the temperature increases, the kinetic energy increases which result to fast moving molecules that causes the breaking of intermolecular bonds that leads the molecules to escape from the solution. Hence, the solubility of the gas will decrease. I'm not sure though if this is the reason.

 

Can someone explain to me more clearly??

[studiot]

The solubility of gasses that dissolve in water, but do not react with the water, decreases with increasing temperature.

 

An example of this would be oxygen, which has a solubility of 1.5 mg/L at 0C and 0.8 mg/L at 30C

 

If, however, the gas chemically reacts with water and this reaction speed increases with temperature, then the solubility will increase.

Edited May 18, 2013 by studiot

[John Cuthber]

Studiot has it half right.

 

For gases that react with water, like HCl, the solubility also decreases when you warm the solution.

He needs to understand that equilibrium happens when the forward and reverse reactions have the same rate.

The gas may well dissolve faster when the water is hot, but the reverse reaction will also be faster.

What dominates the overall effect is the T S term in the Gibbs energy.

[studiot]

Studiot has it half right.

 

Indeed???

 

I think I have it all right.

 

However I was suitably vague about the case when there is a chemical reaction involved, because I do not know the circumstances.

 

I do know that two (or more) substances undergoing a chemical reaction are not in equilibrium.

 

I do not think bringing in more advanced thermodynamics adds to clarity.

 

Let us suppose that we have an inert sealed container, partly filled with water and having an oxygen containing atmosphere above.

 

Some of the oxygen will dissolve in the water, there will be no chemical reaction so my first condition will pertain namely that the % dissolved oxygen will decrease with increasing temperature.

 

Now let us introduce a quantity of finely divided iron into the water. Over time there will be a chemical reaction between the iron and the hydrated oxygen (the iron will rust) which will remove oxygen from the water, allowing further oxygen from the atmosphere to dissolve. Eventually it is possible that all the oxygen will be removed from the sealed atmosphere this way.

 

The rate of this process will increase with temperature.

 

But things are more complicated and the rate of solution involving a chemical reaction may increase, decrease or show a definite maximum at some preferred temperature.

 

I did wonder if this was about the solubility of aerial carbon dioxide in seawater.

Edited May 18, 2013 by studiot

[John Cuthber]

No, lets not consider those hypothetical issues.

Lets look at the solubility of hydrogen chloride in water.

If you warm up some conc HCl the gas comes off.

 

So, while adding more advanced thermodynamics may not make it clear, it has the advantage of giving the right answer.

 

If your ideas don't agree with reality, it isn't because reality has made a mistake.

[studiot]

I do not propose to enter a childish debate with someone who is labelled a resident expert on this site, so I am reporting the issue and personal way it has been presented for moderation.

 

I did not in any way dispute what would happen with your hydrogen chloride - water system.

 

I simply used a simple example that has been part of the UK chemistry syllabus since before GCSE was invented. In that case the process is different.

 

Is the UK secondary school chemistry realistic?

Well I have personal experience of measuring this effect in bridge post tensioning cables at different temperatures and the rate of corrosion is markedly lower in winter.

 

go well.

 

[John Cuthber]

If you want to avoid being criticised don't make statements like "If, however, the gas chemically reacts with water and this reaction speed increases with temperature, then the solubility will increase." as if they are factual.

The OP has the answer pretty much right, but you told them the opposite so, while I may well have been very impolite, I think you were the first to do so.

 

And, for the record, stating that "If, however, the gas chemically reacts with water and this reaction speed increases with temperature, then the solubility will increase." does "dispute what would happen with your hydrogen chloride - water system."

[gwiyomi17]

When the temperature of a solvent goes up, the solubility of a gas solute goes DOWN.

Now I understand a little bit.

Thanks for the help.