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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