balancing act... water...

[Essjay]

Ah, misunderstood.



Ions cannot exist in isolation, they must be 'paired' with another ion of opposite charge. Carbonate and bicarbonate are anions, that is they are negatively charged, so they have to be paired with positively charged cations - such as magnesium and calcium. But it's the carbonate and bicarbonate which react with acids so those are the buffers. Calcium and magnesium are present but they do not take part in the buffering.
Calcium and magnesium carbonate and bicarbonate are salts and, by definition, any soluble salt totally dissociates in water into its ions. The calcium and magnesium ions are not physically bound to the bi/carbonate ions, they are just in the water at the same time to balance the charge. They don't take part in the buffering process so we can't say that calcium and magnesium are buffers, just that the bi/carbonate ions act as buffers.

 

[StevenF]

Calcium and magnesium carbonate push the PH of water to 7. Not higher not lower. they dissolve in acidic water but in high PH water they precipitate out as a solid. GH is the only test you should look at to measure the hardness of water. It is specific to calcium and Magnesium.

KH measures carbonate not calcium and magnesium. So KH will also detect sodium bicarbonate, potassium bicarbonate, and many other carbonates Some will push the PH well above 7 while others will have little impact on PH.
;
To push the PH down you need add an acid to the water like sulfuric acid or hydrogen chloride. it doesn't take a lot to drop the PH to below 6. CO2 is also an acid but a very weak one. You need a lot of CO2 get to a PH of 6.

 

[Colin_T]

Ah, misunderstood.

Ions cannot exist in isolation, they must be 'paired' with another ion of opposite charge. Carbonate and bicarbonate are anions, that is they are negatively charged, so they have to be paired with positively charged cations - such as magnesium and calcium. But it's the carbonate and bicarbonate which react with acids so those are the buffers. Calcium and magnesium are present but they do not take part in the buffering.
Calcium and magnesium carbonate and bicarbonate are salts and, by definition, any soluble salt totally dissociates in water into its ions. The calcium and magnesium ions are not physically bound to the bi/carbonate ions, they are just in the water at the same time to balance the charge. They don't take part in the buffering process so we can't say that calcium and magnesium are buffers, just that the bi/carbonate ions act as buffers.

You smart little scientific chemistry type of humanoid creature thingy. Your not human, are you. Humans don't understand chemistry

 

[Essjay]

But a chemistry department at a university is a good dating place In my class, graduating in 1974, there were 8 female students. 3 of us married classmates, including me . That's probably why one of our two children has a doctorate in chemistry.