WHat is in limestone? (1 Viewer)

[LaurenB]

I can't find the equation for limestone is it CaHCO3? or CaCO3? and how does it react with carbonic acid? HELP!

 

[Paroissien]

Limestone is calcium carbonate CaCO3.
The other formula you have their appears to be calcium hydrogencarbonate. Not sure if it has a common name.
Why do you want to know how it reacts with carbonic acid?

 

[Xayma]

Limestone is CaCO₃

It just pushes the reaction to the left ie.

CO_2(g)+3H₂O_(l) <-----> CO_2(aq)+3H₂O_(l) <-----> H₂CO_3(aq)+2H₂O_(l) <-----> HCO_3(aq)^-+H₂O_(l)+H₃O_(aq)⁺ <-----> CO_3(aq)^2-+2H₃O_(aq)⁺

If hte carbonate dissolves it pushes this equilibrium to the left as you increase the concentration. Which is what normally happens with an acid and carbonate (even if it only has very little solubility), the carbonate dissolves, it pushes it to the left, allowing more carbonate to dissolve etc.

 

[Paroissien]

Limestone is CaCO₃

It just pushes the reaction to the left ie.

CO_2(g)+3H₂O_(l) <-----> CO_2(aq)+3H₂O_(l) <-----> H₂CO_3(aq)+2H₂O_(l) <-----> HCO_3(aq)^-+H₂O_(l)+H₃O_(aq)⁺ <-----> CO_3(aq)^2-+2H₃O_(aq)⁺

That in the syllabus?

 

[LaurenB]

i just wanted it for acid rain, our teacher said it was a good example...another question...whats in limewater?

 

[Xayma]

You should know it.

Carbon dioxide dissolves, it will only be in negligible quantities in the next stage, then it forms H₂CO₃ ie Carbonic acid which undergoes two step ionisation.

 

[Paroissien]

I could be wrong, but I'm quite sure for acid rain questions they will specifically ask you to refer to oxides of sulfur and nitrogen, and how they form acid rain.
I cannot see the need for knowing anything about carbonic acid in reference to acid rain.

 

[smallcattle]

limestone react with carbonic acid will get you calcium bicarbonate

CaCO3 + H2CO3 <-----> Ca(HCO3)2

i think @_@ or am I wrong again..

 

[bobbie212]

hey is limestone a naturally occuring base?

 

[Xayma]

If it is dissolved in water yes.

The CO₃^2- ion being a weak base.

 

[grimreaper]

I think the main equation that you might want to know involving limestone is

CaCO3 + H2SO4 --> Ca(2+) + SO4(2-) + CO2 + H2O

Thats for acid rain weathering limestone though

 

[Paroissien]

Yeah I have to agree. That is the only one I've come across while sticking to the syllabus

 

[Xayma]

Well that is the main compenent of acid rain, rain is normally slightly acidic due to the carbonic acid.

 

[Paroissien]

True, but I've never seen a question referring to that, except for the multiple choice one. Every acid rain question I've seen refers to sulfur and nitrogen.
Correct me if I'm, wrong

 

[Xayma]

No Carbon dioxide dissolving doesn't do much at all to the pH makes it about 5 or 6 I think. About the same as flat soft drink.

 

[Paroissien]

Nice, because at the moment I'm not worrying about anything that won't be in the exam