Hi, everyone. May I know why carbon dioxide is acidic? Also, will carbon dioxide gas dissolve in water to form hydrogen carbonate? Thanks.

Carbon dioxide is acidic because in reaction with water give an acid.

 

[ce]CO2 + H2O -> H2CO3[/ce]

Carbon dioxide is acidic because in reaction with water give an acid.

 

[ce]CO2 + H2O -> H2CO3[/ce]

 

FWIW, this is why "pure water" is such a misnomer. I am "into" live steam locomotive modelling, and the literature all says distilled water is acidic, and therefore corrosive to steam boilers.

 

My chemistry texts all say distilled water is pure water, and has a Ph of 7.0. Nonetheless, if you buy some distilled water, or make some yourself, you will find upon measuring, it's Ph will be less than 7.0.

 

As soon as even a minor surface area of distilled water is exposed to air, it gobbles up CO2 and becomes Ph < 7.0.

 

H2CO3 in solution contributes those H+ ions, making it acidic. Strictly speaking, gaseous CO2 is not "acidic" since it contains no H+ atoms. imp

[ce]

CO2 + H2O <-> H2CO3

[/ce]

 

[ce]

H2CO3 + H2O <-> HCO3- + H3O+

[/ce]

 

[ce]

HCO3- + H2O <-> CO3^2^- + H3O+

[/ce]

 

Note that the [ce]<->[/ce] means it is a reaction that goes both ways: it is an equilibrium.

 

p.s. how do I properly write CO3(2-) with the 2- in superscript?

 

Edit: thanks, YT2095 (post #5)

[ ce]CO3^2^- [ /ce] did the job even better.

[ ce] CO3(^2-)[ /ce] try that.

also, a note to imp, a substance doesn't have to contain H+ to be acidic. Look up lewis acids and bases.