Question

For each of the following pairs, state which is a stronger aqueous acid and explain why:

A) H₂S or H₂Se

B) H₂SeO₄ or H₂SeO₃

C) CH₃COOH or CBr₃COOH

D) Cr(H₂O)₆³⁺ or Cr(H₂O)₆²⁺

Answer 1

A) H₂Se is stronger acid than H₂S because the H–Se bonds is longer than that of H–S bonds due to larger size of Se than S. Thus, the H–Se bond is weaker than the H–S bond and ionizes easier.

B) H₂SeO₄ is stronger acid than H₂SeO₃ because H₂SeO₄ has one more oxygen on central atom.

C) CBr₃COOH is stronger acid than CH3COOH because CBr₃ has more electronegativity than CH₃.

D) Cr(H₂O)₆³⁺ is stronger acid than Cr(H₂O)₆²⁺ because greater the charge density on the central cation, the greater the extent of deprotonation and the more acidic the solution.