Dissolution of calcium carbonate in nitric acid, then combustion

[shafaifer]

Hello,

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).

 

 

 

 

[Enthalpy]

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⁺.

[rktpro]

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.

[John Cuthber]

The reducing agent is something like hydrogen, or even a free electron, from thermal dissociation of water.

Flame chemistry does things that never happen in test tubes.

[shafaifer]

I thank you all very much.