Q92 E - Chemistry (OpenStax)

Question

Which is the stronger acid, \({\rm{NaHS}}{{\rm{O}}_3}\)or \({\rm{NaHS}}{{\rm{O}}_4}\) ?

Step-by-Step Solution

Answer

 \({\rm{NaHS}}{{\rm{O}}_4}\) is the stronger acid.

Step 1: To find the stronger acid.

\({\rm{NaHS}}{{\rm{O}}_4}\) is a salt of stronger acid and therefore a stronger acid. 

Reasoning is the one double bonded oxygen atom more on the sulfur atom which in unprotonated state helps with delocalization of electron, making a \(SO_4^{2 - }\) ion more stable than the\(SO_3^{2 - }\)ion.
Dissolution of the salt: \({\rm{NaHS}}{{\rm{O}}_4}(s) \to {\rm{N}}{{\rm{a}}^ + }(aq) + {\rm{HSO}}_4^ - (aq)\).
Deprotonation of acidic ion: \({\rm{HSO}}_4^ - (aq) + {{\rm{H}}_2}{\rm{O}}({\rm{l}}) \to {\rm{SO}}_4^{2 - }(aq) + {{\rm{H}}_3}{{\rm{O}}^ + }(aq)\).