Question

Which of the following statements is true?
(a) H₃ PO₃ is a stronger acid than H₂SO₃
(b) In aqueous medium HF is a stronger acid than HCl
(c) HClO₄ is a weaker acid than HClO₃
(d) HNO₃ is a stronger acid than HNO₂.

Answer 1

(d) : Higher is the oxidation state of the central atom, greater is the acidity.
Hence, HClO₄ is a stronger acid than HClO₃. HNO₃ is a stronger acid than HNO₂.
Now, greater is the electronegativity and higher is the oxidation state of the central atom, greater is the acidity. Hence H₂SO₃ is a stronger acid than H₃PO₃.
Due to higher dissociation energy of H – F bond and molecular association due to hydrogen bonding in HF, HF is a weaker acid than HCl.