# How did they come up with this completed reaction

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

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

There is a Na missing.

The HCO3 breaks down as follows:

HCO3 + H2O ⇔ H3O+ + CO2

Where does the charge comes from?

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

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

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.

Last edited:
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 ??

There is a Na missing.

Where does the charge comes from?

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

I believe it goes:

H2CO3 + 2H2O ⇔ HCO3- + "H3O+" + H2O
HCO3- + "H3O+" + H2O ⇔ CO32- + 2"H3O+"
CO32- + 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) ⇔ CO32- + 2H+(aq)
CO32- + 2H+(aq) ⇔ H2O + CO2

Borek
Mentor
you get a net equation that looks like:

H2CO3 ⇔ H2O + CO2

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

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

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