Calcium carbonate vs. Magnesium Carbonate reaction with acid.

[Andrew H]

I am trying to engineer an aquarium system that will maintain CO2 levels much higher than what is present if the atmosphere. I have many ideas to create these conditions. However, the avenue of producing CO2 through a chemical reaction is one that is giving me most trouble. I know how it works and understand the equations. Although I don't know how to quantify the CO2 release for this reaction do you quantify the about of CO2 being released in these two First of all I would like to learn reaction produced more CO2. I am asking this because I read some where that MgCO3 produced a lot more  CO2 than CaCO3 does under the same conditions but it didn't explain why. I hadn't though about this much before but the amount CO2 produced by MgCO3 was so much greater it really had me wondering if it was true. If someone knows the answer and is willing to explain it to me I would appreciate it. 

CaCO3 + HCL > CaCl2 + CO2 + H20

or

MgCO3 + HCL > MgCL2 + CO2 + H2O

[John Cuthber]

Na atom of Ca weighs more than an atom of Mg.

So, a molecule of MgCO3 weighs less (84.3/100.1)  than a molecule of CaCO3.

I'd not call that a lot more CO2 per gram, but it's more.

I suspect that on a dollar for dollar basis, CaCO3 is better.

 

[Andrew H]

 

I have few more questions and one is about Dolomite. How does CaMg(CO3)2 disassociate and behave in slightly acidic water? I know from gardening that limestone powder raises pH faster that dolomite powder especially when watered into the acidic soil. Does means that Ca CO3 reacts faster with acids in solution than MgCO3?  If reaction time with acids is significantly faster in CaCO3 this could be a useful tool to help maintain elevated CO2 levels. Because magnesium is bonded to the carbonate ion stronger than calcium is I think predicting how carbonate rocks with different Ca:Mg ratios will act over time can be done.

Thank you for your time.