I find that many gases of the form $\ce{MO_2}$ like $\ce{SO2}$ , $\ce{CO2}$ and $\ce{NO2}$ dissolve in water to form acids. This observation has many different practical implications, for example, it is due to sulphur dioxide and nitrogen dioxide mixing with water vapour in air that acid rain is formed.

My question is why does mixing of gases into water make them into aqueous acids?

  • 1
    $\begingroup$ May be due to high electronegative ness of $\ce{S,C,N}$ (compared to metal oxides they make bases) those atoms are combined to $\ce{O}$ even more electronegative atom, Having a $\ce{H}$ to $\ce{O}$ will reduce this effect even better acid give away the proton and makes the acid anion more stable $\ce{O}$ having a minus charge. $\endgroup$
    – Avon97
    Aug 6, 2021 at 13:39
  • $\begingroup$ That is a good way to think about @Avon97 $\endgroup$ Aug 6, 2021 at 13:41
  • 3
    $\begingroup$ It isn't true in general. Some, well-known, gases do form acids but many others do not. So the question really should read "why do some gases dissolve in water to form acids". $\endgroup$
    – matt_black
    Aug 6, 2021 at 16:06
  • $\begingroup$ Usually non-metal oxides are reacting with water to produce acids. Some do not react at all, but none produce an hydroxide or a base, in contact with water. To my knowledge, this can be considered as a definition of non-metals. $\endgroup$
    – Maurice
    Aug 6, 2021 at 16:52
  • 1
    $\begingroup$ As noted by matt_black and Maurice, one example I could think of is chlorine dioxide($\ce{ClO2}$). It doesn't hydrolyze in water. Hence, it is handle as a dissolved gas solution in water. $\endgroup$ Aug 7, 2021 at 2:41


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.