Acid + Carbonate = what reaction?

A. Hi Harri. The reaction is the same as shown under September 25, 2012 except using acetic acid ⇦this on eBay or Amazon [affil links] rather than hydrochloric acid. The acetic acid converts the calcium carbonate to calcium acetate, water, and oxygen.

It is difficult to explain "why" because the depth of explanation should depend on what grade you are in (what depth of knowledge you already have that we can build on), and because as Richard Feynmann told us, no matter how deeply we study, we actually only learn "how" in greater and greater depth, we never learn "why" :-)

But in reasonably simple terms, the reason it does this is that the reaction products have a lower energy state than the original ingredients. So putting the ingredients together releases a small amount of heat, and as the heat dissipates, the reaction flows one way instead of back and forth. And once the carbon dioxide fizzes off, it's no longer there, further preventing the reaction from reversing. If you have a coin standing on edge on a table, and you shake the table, the coin will fall over on its face and stay there. Further shaking is very unlikely to get it back up on its edge because it's at a lower energy level when it's lying on its face. In the same way, heat is released by this reaction, so it doesn't flow the opposite way.

Regards,

A. Hi, Miles.

I would have doubted it. Most simple reactions are exothermic. I believed that reactions involving acids plus metal carbonates are exothermic. But I see a PhD on the internet describing an experiment proving it to be endothermic. I think the idea of your lab is to put a thermometer into the reaction cup before during and after, and see whether the thermometer reads higher (exothermic) or lower (endothermic) as the components mix. Good luck!

Regards,

A. Hello Miles,

There are many variables making this kind of reactions endo or exothermic. As they have as result a gas (and the reactives are liquid or solid), the final entropy of the system is many times higher as the initial entropy. This has no relation with enthalpy variation (negative means endothermic, positive means exothermic).

Enthalpy is just an experimental value, that can be measured theoretically with some physicochemical models, but its root is in experimental values. There are tables with enthalpy values that can help people to estimate enthalpy variation, thus being able to tell if a reaction is exo or endothermic.

So, there are infinite possibilities... Good luck!

A. Dear Emma,

The carbonic acid is very unstable as itself, as it cannot be measured with any instrument. There are theories that mention the carbonic acid as an intermediary to carbon dioxide and water, but the state "carbonic acid" readily decomposes because of the low energy and high entropy of the product states.

It is, the most energetic and organized state, tends to decompose into lower energy and more disorganized states. As you are forming a gas, the product state is very disorganized, and thus the entropy is high.

Carbonic acid is a theoretical substance that we cannot handle in experiments, so its energy must be very high, and so it is very unstable. Some facts in chemistry are empirical, and so comes a theory (later) that sustains the fact ;)

Hope this clear some of your doubts! Regards,

Thank you! That really helps and that's probably why I couldn't find a whole lot of information :)

A. Hi Sudhakar. I'm happy to help, but believe it's injurious to education to offer an answer unless the student understands the question. To assure me, please write the left hand side of the equation, and I'll supply the right. Please remember that in writing chemistry formulas, proper spelling and capitalization are essential; anything less is an outright error that may get you flunked. Good luck.

Regards,

A1. Hi. Navrishka. Can you give us an example of a non-metallic oxide and tell us what "acidic in nature" means to you, so that we are confident that you truly understand the question you are asking?

A2. Slaked lime is Ca(OH)₂. It may be a solid or it may have water added and be a solution. Limewater is a "saturated solution" of slaked lime. I.e., if you add slaked lime to water, and keep going until no more can dissolve and it starts accumulating as a sludge at the bottom, and then you put it through a filter so none of the sludge gets through, so you have the maximum possible amount of slaked lime dissolved in water, that is lime water.

Regards,

A. Here's an answer from a chemist; probably TMI.

You have 3 cations, H+, Na+ and Ca++.

And 4 anions, OH-, benzoate (not benzonate; I'd be pretty sure of that), chloride, and acetate (from vinegar, which is acetic acid).

So 12 salts are produced; they are partially or completely ionized, are in solution with the cations and anions themselves, all in equilibrium with one another.

A. Hi folakemi. It is necessary to allow the carbon dioxide to be expelled because it occupies more volume and could explode a sealed test tube.

Are you sure you understand the question that you have posted though? People can help answer your posted questions, but if you post your teacher's question like a parrot, without understanding it, it's a problem. Tell your teacher if you don't understand the question.

Good luck.

Regards,

Hi Alyanna. Sorry, I've never heard of HCI, and doubt that it exists. It could just be a typo, but are you sure that you at least clearly understood your homework assignment?

Regards,

A. I have also never heard of HCI and doubt if it is a possible material. Your HCI is probably HCl. Ask your teacher.

Most text books have this or a similar reaction in the text.
If not try the internet.

With HCl, it is a very common reaction. Note the conservation of mass in blue print in Ted's answer.

A. Alyanna,
Back in the day before widespread internet, students needing help would have to ask one of their classmates or even the teacher. Somehow I suspect either of these would still be faster than an internet forum.

Of course one can't be blamed too much for confusion between, let's say, a lowercase l, a capital I, and the number 1. However, chemistry students are expected to be familiar enough with the common elements to be able to pick out when something is likely to be chlorine. HCl is of course hydrochloric acid.

At this point it would be apt to point out that hydrochloric acid is a strong acid, and carbonic acid is a weak acid. If you are familiar with conjugate bases (or able to look that up right now), that should tell you something about what's going to happen first. Carbonic acid also has a very special property that I'm sure your textbook talks about, and I know Wikipedia talks about, that plays an important role in what happens after that.

A. Larry,
Quick hint: Look up carbonic acid on wikipedia, that will give you two key pieces of information about what carbonate will do in the presence of a strong acid.

A. Yes, it is a neutralization reaction. It is also a replacement reaction. It is also an exothermic reaction. The amount of CO2 will somewhat depend on rate of reactions/strength of the reactants. It is possible for some to remain a ionic carbonate. Resulting pH will be a result of how complete the reaction is and how much of an excess of either component is.

A. Kiri,
Calcium carbonate CaCO3
and
sodium acetate NaCH3COO
are both salts. Mixing them won't cause any reaction.

You wrote out an equation using calcium hydroxide Ca(OH)2, but again, everything will just dissociate into water, there is no real reaction there. Note that the equation you wrote is not balanced. You should have just stopped at
Ca(CH3COO)2 + 2 NaOH
but all that does is swap the cations around, which is meaningless when all the compounds listed are soluble.

So then your second reaction equation, calcium carbonate + sodium acetate + acetic acid
CaCO3 + NaCH3COO + CH3COOH

Now I'll give you two hints. Ignore the cations and the acetate ion, and read above my January 8 2016 reply to Larry. This would be more involved if given specific amounts of each and asked to find the final equilibrium concentrations, but just a matter of "what reaction will occur" is simple enough.

A. Hi John. I count one Hydrogen and one Cl atom on the left side of your equation, and two of each on the right. Your error is a very small one, and perhaps only typographical, but before you ask a question about a reaction, you must write it in excruciatingly correct form because if it's not balanced it's nonsense and it doesn't make any sense to talk about it at all.

Yes, it's a neutralization reaction! But just because you believe that a particular dog is large doesn't mean he can't also be a black dog or a friendly dog. You'll need to study what a decomposition reaction is, and what a double displacement reaction is, and decide whether the reaction between CaCO3 and HCl qualifies or not because we can't assume it's a multiple choice question :-) ... but I don't believe it to be a decomposition reaction or a double displacement reaction. Good luck.

Regards,

A. Hi Or. Yes, that sounds like a good experiment, and good questions for the experiment to answer.

But you can't get more carbonate in the limescale than was in the water, so you obviously won't get much limescale without significant carbonate in the starting water. Good luck.

Regards,

A. Hi Magdeline. vinegar is acetic acid, a mild acid. The scale is calcium carbonate.
As you see on this page, mild acids like vinegar will react with the calcium carbonate and dissolve it.

The Ladies No. 1 Detective Agency, set in Gaborone, is an all-time favorite book series, so I'm always delighted to receive a letter from Gaborone :-)

Regards,

A. Hi Mona. Hopefully, if you just read this one page you will be well on your way towards understanding.

The teacher gives you the aim. Charles Darwin himself said that to try to do science without a hypothesis is to waste your life in a gravel pit sorting the stones by size and color.

In seventh grade I doubt that you are supposed to determine the materials and procedure yourself; that would be too dangerous at your age. Again your teacher gives you this.

Your observations are what you see and note when you follow the procedure -- any and all detectable changes. The result is your conclusion about what probably happened. A conclusion does not have to be airtight like a proof in mathematics; it may include suggestions for what should be done next time to strengthen the conclusion.

Regards,

A. Hi Ishad. I'm not sure that your equation is actually wrong; it looks okay to me. But there is a proviso, because the subsequent equilibrium reaction:
H2CO3 <-> H20 + CO2
shifts very strongly to the right. So
CaCO3+2HCl→CaCl2+H2O+CO2
is probably closer to the actual situation.

CaCO3 is quite insoluble, so I'm not sure the '(aq)' really belongs next to it, '(s)' might be better; but '(aq)' seems an appropriate description for the state of the other compounds. Good luck.

Regards,

A. Hi cousin Palmalaya,
copper sulphate crystals are CuSO4.5H2O. It seems to me that burning the mixture will drive off those five parts of water so you can't get the crystals you seek.

Regards,

A. Hi Janet. I'm not sure that you fully understand the question, and I don't really like to offer answers if the question isn't understood because it wouldn't help your education … but what do you think would happen regarding the amount of evolution of carbon dioxide if, as soon as the sulfuric acid started dissolving the lead carbonate, you pulled out your remaining lead carbonate and coated it with acid-resistant glass and then put it back in the acid?

Regards,

A. Hi Isabel. I think the idea is to let your acetic acid and your calcium carbonate stabilize to room temperature, put the bulb of a thermometer into the dish of calcium carbonate crystals, then pour the acetic acid onto them while observing what happens to the temperature as the reaction takes place.

Although it's not true of 100% of cases, most chemical reactions of that general sort do produce heat.

When I was a kid I had an older sister who I naturally wanted to play with; and being an older sister she sometimes didn't want to. So one day when I nagged her she invited me to play "52 pickup", which it turned out consisted of her taking two seconds to throw a deck of cards around the room and me having to spend 5 or 10 minutes picking them all up.

The lesson being that it takes much less energy (heat) to move things from a state of order into disorder than it takes to move them from disorder back to order. It's easy to mix acetic acid and calcium carbonate; it's quite hard to make the reaction run backwards to get the starting materials back; that's an indication that when they mixed they probably released energy (heat) and that it will require energy to restore them.

Regards,