Reef Chemistry Question of the Day #75 Precipitation of Calcium Carbonate

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #75

When calcium carbonate precipitates on pumps in a reef aquarium, what is the effect of that precipitation on the pH of the water?

A. It rises
B. No change
C. It drops
D. It may do either

Good luck!






























.

 

[Zero Nitrates]

A It rises!

 

[Sangheili]

No change

 

[beaslbob]

d. Could go either way

 

[Cory]

I'd say C because iirc it takes bicarbonate and calcium to form calcium carbonate and since bicarbonate contributed to alk, and alk to PH, my logic says it will drop, although it would be a very small and unnoticeable amount in reef aquaria unless the amount of precipitation is larger than the typical powerhead and heater calcium carbonate precipitate.

 

[billwill]

I'd say C because iirc it takes bicarbonate and calcium to form calcium carbonate and since bicarbonate contributed to alk, and alk to PH, my logic says it will drop, although it would be a very small and unnoticeable amount in reef aquaria unless the amount of precipitation is larger than the typical powerhead and heater calcium carbonate precipitate.

What he said!

 

[Cory]

I might sound smart, but I'm really not.

 

[Randy Holmes-Farley]

We'll see when the answer posts.

 

[Randy Holmes-Farley]

Anyone else before I give the answer?

 

[naecO rM]

I think the answer is D.
If PH level is too high calcium Carbonate precipitated on pump.
If pH level is too low Calcium can be desolve more in the water and calcium level can be higher than with low PH level.

 

[H2O]

A. final answer

 

[naecO rM]

A. final answer

It's working another way.
Calcium Carbonate precipitation is depend from PH level.

 

[Randy Holmes-Farley]

It's working another way.
Calcium Carbonate precipitation is depend from PH level.

Yes, but it also has an effect on pH.

 

[Randy Holmes-Farley]

And the answer is...C. It drops
Cory had the right answer, and for part of the right reason.

There are two effects that make it drop, but the first one is instantaneous and not dependent on any other factors, and hence is the primary reason for the answer.

1. When you remove carbonate, you cause a shift in the equilibrium between bicarbonate and carbonate:

HCO₃^- <---> CO₃^-- + H⁺
which reads as
Bicarbonate <--> Carbonate + Proton

By Le Chatlier's Principle, if you remove something from one side of an equilibrium, the reaction ***** to replace some of it.

So in this case, if you remove carbonate, some of the bicarbonate splits apart into carbonate (to replace what was lost) and the released H+ (which lowers pH).

2. If you actually allow the carbonate to be removed and don't replace it, the total alkalinity declines, and that decline in alkalinity will reduce the pH of seawater in equilibrium with the air.

Happy Reefing!

 

[Randy Holmes-Farley]

Another way to think about this is as follows:

Many people know that adding carbonate as an alkalinity additive boosts pH.

So removing the same thing must lower pH.

 

[Cory]

Wow I feel so intelligent I might start calling myself Randy for a while.

 

[Randy Holmes-Farley]

:lol:

Happy Reefing.

 

[Rybren]

I am so SMRT

 

[beaslbob]

well I blew another one.

 

[naecO rM]

Yes, but it also has an effect on pH.

So I'm part right. Isn't it?
If PH level is too high a Calcium carbonate parcipited on pumps or heaters. is that correct?
So the second part is
partcapitation of calcium Carbonate does decreasing for PH. Is that correct?

What is a balance between PH and Ca?
When parcipiyayion can be stops?
Both are depended.