PH and KH relationship

[samchuapy]

Hi Seniors,

Can anyone explain is it true that a stable PH (Btwn 8.0 ~ 8.3) means that dosing of KH is not required? Thks

[Martian]

I din know that unstable PH need to dose KH...

[samchuapy]

Sorry abt the chemistry, cos very confuse with ph and KH. Are they measuring the same thing? Both is testing on alkalinity or water hardness izzit?

[Clement Chen]

i was told by the lfs to does liquid kh to reduce the fluctuations in ph

[veliferium]

Sorry abt the chemistry, cos very confuse with ph and KH. Are they measuring the same thing? Both is testing on alkalinity or water hardness izzit?

pH=amt of H ions in the water

kH=amt of carbonates in the water

High kH (7-12dkH depending on individuals for marine aquariums)will keep the pH stable and in check(pH8.0-8.5)

[solasido]

Just trying to share here.

The confusion starts probably from the method of testing/measuring it.

Since measuring pH is easier than measuring carbonate, test kits uses the same method to measure pH to test the concentration of carbonate ions and derived KH from there.

Some facts and the correlations:

* The more H+ ions the lower the pH

The less H+ ions the higher the pH

* KH is primarily consists of carbonate and bicarbonate

* carbonate + H+ = bicarbonate

This is the pH buffering capability

With enough carbonate, any attempt to lower the pH (ie. adding H+ ions) will be prevented by carbonate ions that will bind with H+ to become bicarbonate because hence the free H+ ions is reduced back, therefore prevents drop in pH.

This part explains correlations between pH and KH.

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[surreal1228]

Just trying to share here.

The confusion starts probably from the method of testing/measuring it.

Since measuring pH is easier than measuring carbonate, test kits uses the same method to measure pH to test the concentration of carbonate ions and derived KH from there.

Some facts and the correlations:

* The more H+ ions the lower the pH

The less H+ ions the higher the pH

* KH is primarily consists of carbonate and bicarbonate

* carbonate + H+ = bicarbonate

This is the pH buffering capability

With enough carbonate, any attempt to lower the pH (ie. adding H+ ions) will be prevented by carbonate ions that will bind with H+ to become bicarbonate because hence the free H+ ions is reduced back, therefore prevents drop in pH.

This part explains correlations between pH and KH.

Sent from my iPad using Tapatalk HD

This is super clear and easy understanding. Thanks bro.

So will bicarbonate become carbonate + H+ ions?

Can I assume dosing carbonate will affect ph a bit since it can take the H+ ions?

Or will bicarbonate will help to stablize PH? Since it won't not change H+ions?

[solasido]

This is super clear and easy understanding. Thanks bro.

So will bicarbonate become carbonate + H+ ions?

Can I assume dosing carbonate will affect ph a bit since it can take the H+ ions?

Or will bicarbonate will help to stablize PH? Since it won't not change H+ions?

Bro,

bicarbonate at tank level pH of around 8 will not much become carbonate + H+ at equilibrium condition with the atmosphere

Dosing carbonate will affect (rise) pH a bit, but there is a limit. Since things in this world always try to reach an equilibrium, at certain high pH level, the ion will start drawing CO2 from the air that will then nullify the pH increase

Adding bicarbonate will initially slightly lower pH due to a little bit of them becomes H+ and carbonate, but after the equilibrium, no more bicarbonate will disassociate. The more bicarbonate ions will help a but to buffer the pH because some of the ions will actually bind H+ as well to become carbonic acid.

Corals consumes bicarbonate, so H+ is supposedly released as Corals build their skeleton.

I found the detail explanation here very good:

http://www.advancedaquarist.com/2002/5/chemistry

The hydroxide, borate, etc. ions quantity are very small compared to carbonate and bicarbonate hence ignored.

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