Chlorine after Cya bond is released

[beautifulpool]

Dear Joyfulnoise and any Chemistry geeks @JoyfulNoise
Can anyone shed light for me here
K
Most agree a) pools need chlorine b) sunlight breaks down chlorine quickly c) a substance cya exists that can extend chlorine’s life up to 8 times d) as cya levels increase chlorine’s ability to kill and oxidize decreases dramatically.
e) FC = 7.5 % * CYA
So for Pool With 100ppm cya, unless FC is greater than 7.5%, a pool with 100 ppm cya has zero ability to sanitize until FC Levels exceed 7.5 ppm
Everything ok so far?

That’s the premise leading to my question
If cya (containing 3 carbon and 3 nitrogen atoms) holds chlorine under the CYA ☂ (cya hotel) for awhile -
Why then -when the CYA HOTEL (nitrogen carbon atoms) release the chlorine for active duty .... why does the chlorine not work as well ? Was chlorine 1) maimed in the initial CYA Bond? Or 2) is cya greedy and and still holding onto too much chlorine-even when pool is needing cya to release it’s bound chlorine to fight germs as pool is gaining additional contaminates.... 3)or does CYA release enough FC and chlorine is in top condition - but because FC spent too much time IN CYA HOTEL - did the bad guys have too much time to reproduce?

 

[cfherrman]

Cya holds onto the clorine, there is a chart on active clorine level you can refer to.

 

[beautifulpool]

Cya holds onto the clorine, there is a chart on active clorine level you can refer to.

Yes indeed. Cya does “hold on” to most of the free chlorine. BUT BUT
The cya releases it at some point - BUT at what point???? cause at some point, free chlorine was holding on to the cya’s nitrogen atom? Or was it that the nitrogen in the Cya molecule was holding onto the chlorine???
?? HELP CHEM GEEKS ???
The chlorine sings “I once was bound -but now I’m free!” But why is the FC not as good at that point as it once was??
I honestly don’t fully understand the chemical exchange there....i do know the results of letting a pool’s cya get up over 200-?‍Ain’t pretty
I think I’m just gonna keep my level at 30ppm and be happy about that! )
My Brain is wanting to understand atoms molecules and hydrogen in the outer valences, but Evidently, this knowledge may be beyond its ability to process

 

[Jimrahbe]

I can't help with a chemical answer, but I can tell you that in Texas, you will burn through a lot more chlorine with a CYA of 30 vs a CYA of say 50 or 60..

Thanks,

Jim R.

 

[ajw22]

I suggest you read ...

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

I think it will answer many of your questions. If not, come back here with questions about what is in that thread.

 

[JamesW]

It has to do with equilibrium.

When chlorine is added to a pool, the main forms are hypochlorous acid and hypochlorite ions.

When you add cyanuric acid (C₃H₃N₃O₃), the cyanuric acid molecules float in the water at random. Some of the hydrogen ions detach.

So, you have hypochlorous acid molecules, hypochlorite ions and cyanuric acid molecules (C₃H₃N₃O₃) all floating in the water just moving randomly.

When a chlorine atom bumps into a cyanuric acid molecule, the chlorine atom will sometimes attach where a hydrogen ion was or even knock a hydrogen ion out and take its place.

Now, you have hypochlorous acid molecules, hypochlorite ions, cyanuric acid molecules and cyanuric acid molecules with chlorine attached(C₃ClH₂N₃O₃) all floating in the water just moving randomly.

When a molecule of hypochlorous acid bumps into something like algae or bacteria, the chlorine oxidizes the algae or bacteria by taking electrons. The chlorine becomes chloride.

When a molecule of cyanuric acid with a chlorine atom attached makes contact with bacteria or algae, the chlorine usually does not oxidize the bacteria or algae because the chlorine is attached to the cyanuric acid molecule.

The bond between the chlorine atom and cyanuric acid molecule is pretty strong, but the chlorine atom sometimes detaches and becomes hypochlorous acid again.

So, at any instant, most of the chlorine is attached to cyanuric acid, but some is hypochlorous acid and hypochlorite.

The amount of hypochlorous acid is determined by the amount of total chlorine and the amount of total cyanuric acid.

The effectiveness of the chlorine depends on the amount of hypochlorous acid and hypochlorite present in the water at any instant.

 

[beautifulpool]

Yes indeed. Cya does “hold on” to most of the free chlorine. BUT BUT
The cya releases it at some point - BUT at what point???? cause at some point, free chlorine was holding on to the cya’s nitrogen atom? Or was it that the nitrogen in the Cya molecule was holding onto the chlorine???
?? HELP CHEM GEEKS ???
The chlorine sings “I once was bound -but now I’m free!” But why is the FC not as good at that point as it once was??
I honestly don’t fully understand the chemical exchange there....i do know the results of letting a pool’s cya get up over 200-?‍Ain’t pretty
I think I’m just gonna keep my level at 30ppm and be happy about that! )
My Brain is wanting to understand atoms molecules and hydrogen in the outer valences, but Evidently, this knowledge may be beyond its ability to process

I can't help with a chemical answer, but I can tell you that in Texas, you will burn through a lot more chlorine with a CYA of 30 vs a CYA of say 50 or 60..

Thanks,

Jim R.

Sure, I’m with ya there.
But answer me this, you mentioned 50-60 ppm Cya...so let’s use that, for sake of example
k
Pool A has 50-60ppm cya
FC = 6ppm

Pool B has 30ppm cya
FC = 3ppm

Pool chemistry is identical in A & B (except for CYA and FC)
Since
The owner of pool C Wanted to help his neighbors (of pool A & B) settle the experiment
he performed ORP TEST on Pool A & B
Pool B scored higher on Oxidation potential .
In this case wasn’t LESS —-MORE??
....why would we add more cya (since after 20-30ppm) The kill time is slowed? If more isn’t more, why do we want it?
If I’m missing something, you have my blessing to point it out to me.

 

[beautifulpool]

It has to do with equilibrium.

When chlorine is added to a pool, the main forms are hypochlorous acid and hypochlorite ions.

When you add cyanuric acid (C₃H₃N₃O₃), the cyanuric acid molecules float in the water at random. Some of the hydrogen ions detach.

So, you have hypochlorous acid molecules, hypochlorite ions and cyanuric acid molecules (C₃H₃N₃O₃) all floating in the water just moving randomly.

When a chlorine atom bumps into a cyanuric acid molecule, the chlorine atom will sometimes attach where a hydrogen ion was or even knock a hydrogen ion out and take its place.

Now, you have hypochlorous acid molecules, hypochlorite ions, cyanuric acid molecules and cyanuric acid molecules with chlorine attached(C₃ClH₂N₃O₃) all floating in the water just moving randomly.

When a molecule of hypochlorous acid bumps into something like algae or bacteria, the chlorine oxidizes the algae or bacteria by taking electrons. The chlorine becomes chloride.

When a molecule of cyanuric acid with a chlorine atom attached makes contact with bacteria or algae, the chlorine usually does not oxidize the bacteria or algae because the chlorine is attached to the cyanuric acid molecule.

The bond between the chlorine atom and cyanuric acid molecule is pretty strong, but the chlorine atom sometimes detaches and becomes hypochlorous acid again.

So, at any instant, most of the chlorine is attached to cyanuric acid, but some is hypochlorous acid and hypochlorite.

The amount of hypochlorous acid is determined by the amount of total chlorine and the amount of total cyanuric acid.

The effectiveness of the chlorine depends on the amount of hypochlorous acid and hypochlorite present in the water at any instant.

Just seeing this .... I’ve got my iced tea... can’t wait to dig in thank you so much for this Im sitting down now to read thru and attempt to get an understanding ??

 

[beautifulpool]

Just seeing this .... I’ve got my iced tea... can’t wait to dig in thank you so much for this Im sitting down now to read thru and attempt to get an understanding ??

This is invaluable to me. THANK YOU SO SO SO MUCH. I plan to re-read it several more times to fully absorb. Question
You mentioned a) hypochlorous acid molecule b) hypochlorite ion. Does the % of the chlorine added to our water that ends up turning into the Hypochlorous acid molecule and the % of Chlorine that ends up turning into the ion, is that in part determined by what our pool pH is before adding the chlorine to our pool?
Does the chlorine hypoclorous molecule have more kill strength than the ion?

 

[beautifulpool]

It has to do with equilibrium.

When chlorine is added to a pool, the main forms are hypochlorous acid and hypochlorite ions.

When you add cyanuric acid (C₃H₃N₃O₃), the cyanuric acid molecules float in the water at random. Some of the hydrogen ions detach.

So, you have hypochlorous acid molecules, hypochlorite ions and cyanuric acid molecules (C₃H₃N₃O₃) all floating in the water just moving randomly.

When a chlorine atom bumps into a cyanuric acid molecule, the chlorine atom will sometimes attach where a hydrogen ion was or even knock a hydrogen ion out and take its place.

Now, you have hypochlorous acid molecules, hypochlorite ions, cyanuric acid molecules and cyanuric acid molecules with chlorine attached(C₃ClH₂N₃O₃) all floating in the water just moving randomly.

When a molecule of hypochlorous acid bumps into something like algae or bacteria, the chlorine oxidizes the algae or bacteria by taking electrons. The chlorine becomes chloride.

When a molecule of cyanuric acid with a chlorine atom attached makes contact with bacteria or algae, the chlorine usually does not oxidize the bacteria or algae because the chlorine is attached to the cyanuric acid molecule.

The bond between the chlorine atom and cyanuric acid molecule is pretty strong, but the chlorine atom sometimes detaches and becomes hypochlorous acid again.

So, at any instant, most of the chlorine is attached to cyanuric acid, but some is hypochlorous acid and hypochlorite.

The amount of hypochlorous acid is determined by the amount of total chlorine and the amount of total cyanuric acid.

The effectiveness of the chlorine depends on the amount of hypochlorous acid and hypochlorite present in the water at any instant.

Thank you so SO SO SO much. ....this is invaluable to me. Not simple, but phrased in terms simple enough for me to grasp ... I even asked a few questions to make sure I was tracking ....when you didn’t respond...?‍I noticed I posted my questions (i assumed i was placing next to your post- as it was Related to the topic) but instead, I posted them to myself?(like I’m gonna know lol)
Kudos to you!
Anybody who can simplify chemistry to a person who posts questions for the chemist to herself deserves “best teacher!”

 

[JamesW]

With no cyanuric acid in the water, the pH does determine the percentage of hypochlorite vs. hypochlorous acid.

The pKa of hypochlorous acid is about 7.53.

1÷(1+10^(7.53 – pH)) = hypochlorite percentage.

For example:

pH..........hypochlorite percentage

8.53..........0.90909
8.00.........0.747
7.53.........0.50
7.30.........0.37

Hypochlorous acid and hypochlorite both oxidize and sanitize, but hypochlorous acid is better at both.

With cyanuric acid in the water, the equation changes because most of the chlorine is bound to cyanuric acid, but the pH does still effect the ratio. The effect is not as great, but it still matters somewhat.

 

[beautifulpool]

With no cyanuric acid in the water, the pH does determine the percentage of hypochlorite vs. hypochlorous acid.

The pKa of hypochlorous acid is about 7.53.

1÷(1+10^(7.53 – pH)) = hypochlorite percentage.

For example:

pH..........hypochlorite percentage

8.53..........0.90909
8.00.........0.747
7.53.........0.50
7.30.........0.37

Hypochlorous acid and hypochlorite both oxidize and sanitize, but hypochlorous acid is better at both.

With cyanuric acid in the water, the equation changes because most of the chlorine is bound to cyanuric acid, but the pH does still effect the ratio. The effect is not as great, but it still matters somewhat.

This is so GREAT! Your numbers showed me why,
My pool uses less chlorine This summer. out of convenience (not cause I was smart enough to know at first lol) I added my acid, prior to adding my chlorine.
(I am fanatical about NOT adding CYA past my desired ?)my pool does better on less CYA-
If I’m understanding correctly your examples
From 8.5 pH giving only 10% of the hypochlorous chlorine molecule -vs hypochlorite (roughly rounding your numbers here )
To 7.3 pH giving almost 70% of the good hypochlorous chlorine molecule
This all makes sense.
This all makes perfect sense
THANK YOU ?

 

[AndyTN]

With no cyanuric acid in the water, the pH does determine the percentage of hypochlorite vs. hypochlorous acid.

The pKa of hypochlorous acid is about 7.53.

1÷(1+10^(7.53 – pH)) = hypochlorite percentage.

For example:

pH..........hypochlorite percentage

8.53..........0.90909
8.00.........0.747
7.53.........0.50
7.30.........0.37

Hypochlorous acid and hypochlorite both oxidize and sanitize, but hypochlorous acid is better at both.

With cyanuric acid in the water, the equation changes because most of the chlorine is bound to cyanuric acid, but the pH does still effect the ratio. The effect is not as great, but it still matters somewhat.

Now, let's see if the 19-year-old working at Leslie's can explain in the same level of detail when the computer printout says you need more "stabilizer" in your pool... TFP for life now!