[lk1982]

Hi everyone,

I am writing a report on an experiment to determine whether a precipitate is a carbonate or a sulfate (in this case magnesium carbonate or sulphate). Nitric acid is made to react with the two precipitates, with the assumption that one will be dissolved by the acid, proving that it is the carbonate, and the other will not react and remain the same, proving that it is the sulphate.
Now I know how carbonates react with common lab acids to give a salt, water and carbon dioxide, as shown in the link below:

http://www.chemistryrules.me.uk/junior/acids.htm

However, I cannot find any information as to why the sulphate will not react with the nitric acid. Do sulphates simply not react with the common lab acids? Why do carbonates react but sulphates do not?

Thank you in advance!!

[Borek]

Do you know a difference between a strong and a weak acid?

Is carbonic acid stable, or does it easily decompose? Is sulfuric acid stable, or does it easily decompose?

[lk1982]

Hi and thank you for taking the time to reply.
Rereading my question, I have noticed that the sulfate and carbonate are barium sulfate and carbonate (not magnesium).
So...

BaCO3 (s) + 2HNO3 (aq) > Ba(NO3)2 (aq) + CO2 (aq) + H2O (l)

and...

BaSO4 (s) + HNO3 (aq) > no reaction

Why are you asking about carbonic and sulfuric acid? I have found that the former is unstable while the latter is stable - how does this relate to the above? Sorry if I am being a little slow in following your reasoning but this is really the first chemistry I tackle in a really long time (15+ years).

[Borek]

Properties of acids and their salts are to some extent related.

You are right - one of the important differences between carbonic acid and sulfuric acid is that the former is unstable.

You have already wrote the almost correct reaction equation:

BaCO3 (s) + 2HNO3 (aq) > Ba(NO3)2 (aq) + CO2 (aq) + H2O (l)

Have you ever seen a reaction of any carbonate with a strong acid?

[lk1982]

Hi Borek,

Yes, when reacted with nitric acid the barium carbonate in my sample fizzled and dissolved. What I do not understand and cannot find any information on is why this will not happen with the barium sulfate as well...

[AWK]

The lack od reaction is also a valuable information.

There is possibility to dissolve  a minute amount of BaSO₄ in hot concentrated strong acids  (H₂SO₄ or HNO₃). Needle shaped crystals of barium sulfate are formed after cooling. But this can be done only in good laboratory under hood.

[lk1982]

Thank you, AWK!
If possible, could you please elaborate a little on why Ba(NO3)2 will readily dissolve in HNO3 whereas BaSO4 will not?? That is really the information that I am looking for.

[Borek]

Yes, when reacted with nitric acid the barium carbonate in my sample fizzled

What does this "fizzling" part mean - does the CO₂ stay dissolved, or is it removed from the solution? If it is removed - can it still react with Ba²⁺ to form precipitate?

What I do not understand and cannot find any information on is why this will not happen with the barium sulfate as well...

This is the "stability" part - sulfuric acid is stable, carbonic is not. And I suggest at this level of knowledge you just accept this information without getting into details, as they will only further confuse you.

[AWK]

Thank you, AWK!
If possible, could you please elaborate a little on why Ba(NO3)2 will readily dissolve in HNO3 whereas BaSO4 will not?? That is really the information that I am looking for.

Read scrutinously Wikipedia or textbook about solubility

[lk1982]

Read scrutinously Wikipedia or textbook about solubility

Thank you. As you are taking the time of day to reply to these messages for nothing in return I realize that it is not my place to complain, but the reason why I am asking on this forum is because I was unable to find - or possibly extrapolate - the information I required on wiki and on the two textbooks I consulted (British A level material).
I apologize if there is a forum rule in place that I have missed stipulating that you cannot answer my question directly. If you are aware of a particular text or resource that I could consult on the subject, I would greatly appreciate it.

[lk1982]

This is the "stability" part - sulfuric acid is stable, carbonic is not. And I suggest at this level of knowledge you just accept this information without getting into details, as they will only further confuse you.

Aaah, the "accepting" part is sort of hard to do, but I see your point. Thanks again for your time!

[AWK]

Read scrutinously Wikipedia or textbook about solubility

Thank you. As you are taking the time of day to reply to these messages for nothing in return I realize that it is not my place to complain, but the reason why I am asking on this forum is because I was unable to find - or possibly extrapolate - the information I required on wiki and on the two textbooks I consulted (British A level material).
I apologize if there is a forum rule in place that I have missed stipulating that you cannot answer my question directly. If you are aware of a particular text or resource that I could consult on the subject, I would greatly appreciate it.

The are at least two levels of explanation - in general chemistry we just use rules, and in physical chemistry we look more deeply in physical background.
In general chemistry we just compare solubility of compounds in water - Ba(NO₃)₂ is well soluble, and BaSO₄ is very poor soluble.
Using HNO₃ for both we should change level of our thinking - we should take into account thermodynamics, the common ion effect, ionic strength and possible equilibria in solution.
My corrections of printing errors

[lk1982]

Thank you so much! I will look into what you have pointed out.