How do you write an acid/base reactions with phases? For example, including phases, write the chemical equation for the reaction of the weak acid HCN with water.

1 Answer
anor277
Aug 7, 2016

#HC-=N(aq) + H_2O(l) rightleftharpoons H_3O^+ + ""^(-)C-=N#

#K_a=([H_3O^+][""^(-)C-=N])/([HC-=N]) = 10^(-9.21)" at "298K#

Explanation:

Of course, the anions and the cations are solvated by, or aquated by, several water molecules. The acidium ion in water, which we represent as #H_3O^+# is likely to be a cluster of several water molecules, with an EXTRA #H^+# ion, i.e. #{H_9O_4}^+# or something similar. The representation of this as #H^+# or #H_3O^+# may even be naive, but it is still useful and practical for calculation.

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