[keb]

Ca (H2 PO4)2(s) + NaHCO3 (s) --> CO2(g) + H20(g) + CaHPO4(s) + Na2HPO4(s)

chemical equation

what happend to the HCO3- ion What is this type of reaction? What is the chemical equation involved?

[Dan]

Show your attempt first, and could you read the Forum Rules please.

[keb]

oh sorry, I wasn't able to read the Forum guidelines.

for letter a., the balanced equation is Ca(H2PO4)2(s) + 2NaHCO3 (s) --> 2CO2(g) + 2H2O(g) + CaHPO4(s) + Na2HPO4(s).

for letter B, I think its a decomposition reaction with HCO3^- --> 2CO2 + H2O. The hydrogen carbonate ion decomposes to carbon dioxide and H2O but I'm not really sure.

Do you think it's correct?

[lavoisier]

Sometimes it's easier to see what happens if you eliminate the non-reacting species. In this case, the metallic cations don't do much, so you can write the anions only:

H₂PO₄^- + HCO₃^- --> HPO₄^2- + H₂CO₃ --> HPO₄^2- + H₂ + CO₂

A proton has been transfered from the dihydrogenophosphate anion to the hydrogenocarbonate anion. The carbonic acid thus formed is unstable and decomposes to water and carbon dioxide.

So there are actually at least two reactions occurring. I don't know what they are 'officially' called like, but as long as you figure out what happens, any teacher should be happy enough.