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Dissolution of calcium carbonate in nitric acid, then combustion


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I have these reactions (they should be correct):

CaCO3(s) + HNO3(aq) --> H2O(l) + Ca2+(aq) + CO2(g) + NO3-(aq) Eq. 1


Calcium cations will now form a complex with water according the following reaction:


Ca2+(aq) + 6H2O(l) --> [Ca(H2O)6]2+(aq) + 6H2O(l) Eq. 2


Now comes the combustion: This is a project of AAS (atomic absorption spectroscopy), and I want to measure the absorbance for calcium when irradiated with a hollow cathode lamp. I am only interested in calcium so I ignore water, nitrate ions and CO2(g). As a combustion agent / oxidising agent, C2H2(g)/O2(g) is used:


[Ca(H2O)6]2+(aq) + C2H2(g)/O2(g) --> Eq. 3


What is the product of this equation? I am sure solid calcium is formed (thus reduced). But how can it be reduced when the compounds used for the combustion are oxidizing agents? I am considering C2H2(g)/O2(g).





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  • 2 weeks later...

Same answer here as on the other forum...


Oxygen and acetylene serve to atomize calcium by heat, so you can observe its absorption. At 3000+°C there is no solid calcium, hydroxide, nitrate...


I wouldn't call acetylene an oxidiser, nor would I put a specific number of water molecules around Ca2+.

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If you want calcium then use something that can reduce it like Lithium, Potassium, Barium etc,like they do in silver extraction from cynide complex. Although, side reactions would be there.

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