How did they come up with this completed reaction

lechatelier

This is what the completed reaction looks like
Na₂CO₃ + 2HCl ⇔ 2NaCl + H₂O + CO₂

My question is how did they get the products in the above reaction.

Here is my attempt, but I don't see how to get it like in the above reaction
Na₂CO₃ + HCl ⇔ NaCl + HCO₃

The HCO₃ breaks down as follows:

HCO₃ + H₂O ⇔ H₃O⁺ + CO₂

So my question is how did they only get H₂O + CO₂ in the top reaction without the hydronium H₃O⁺ ??

Thanks

DrStupid

There is a Na missing.

Where does the charge comes from?

Borek

Apart from what DrS wrote, solution of HCl contains plenty of H⁺.

HeavyMetal

Well, the first equation you gave us is balanced. The reactants and products both contain:

3 O
2 Na
2 Cl
2 H
1 C

However, your second equation is missing a coefficient in front of one of the reactants. You wrote: Na₂CO₃ + HCl ⇔ NaCl + HCO₃. This is not balanced properly, because on the reactant side you have 2 Na, and on the product side you only account for 1 Na. If you add a two in front of the HCl in the second equation, you get the correct products for the completed reaction of:

Na₂CO₃ + 2HCl ⇔ 2NaCl + H₂O + CO₂.

lechatelier

Heavymetal:

It's not a question about balancing!!

I could balance the equation no problem. The question is why the reaction doesn't go this route:

Na2CO3 + 2HCl ⇔ 2NaCl + H2CO3

The H2CO3 breaks down as follows:

H2CO3+ H2O ⇔ H3O+ + HCO3

The HCO3 breaks down as follows:

HCO3+ H2O ⇔ H3O+ + CO3

So I got H3O+ + CO3 but why is it that the correct reaction has H2O + CO2 (at the top, at the beginning of this post) without the hydronium ion H3O+ and CO3 ??

lechatelier

Are you serious in asking me where the +ive charge on a hydronium ion came from????

HeavyMetal

I believe it goes:

H₂CO₃ + 2H₂O ⇔ HCO₃^- + "H₃O⁺" + H₂O
HCO₃^- + "H₃O⁺" + H₂O ⇔ CO3^2- + 2"H₃O⁺"
CO3^2- + 2"H₃O⁺" ⇔ 3H₂O + CO₂

I say "H₃O⁺" because it doesn't actually take shape of the hydronium ion here. So if you cancel out the 2 H₂O from the beginning, and the 2 out of the 3 in the end, you get a net equation that looks like:

H₂CO₃ ⇔ H₂O + CO₂

However, it probably looks more like this:

H₂CO₃ ⇔ HCO₃^- + H⁺_(aq)
HCO₃^- + H⁺_(aq) ⇔ CO₃^2- + 2H⁺_(aq)
CO₃^2- + 2H⁺_(aq) ⇔ H₂O + CO₂

Borek

That's the main equation here, everything else is just an alternative take on the several equilibria present in the solution.

DrStupid

Yes, I do. The net quantity of electric charge must not change.