Question

For each group of compounds listed, which is the strongest acid? I. HIO2, HIO3, HIO4 II. H2Se, H2S, H3As III. HPO2, HClO2, HBrO2

Answer 1

Answer:

In group I, strongest acid is $HIO_4$

In group II, the strongest acid is $H_2Se$

In group III, the strongest acid is $HClO_2$

Explanation:

Group I:

Acidic strength depends upon the stability of conjugated base formed after release of H+.

In the given acids, after releases of H+ following conjugate bases are formed:

$HIO_2 \rightarrow H^+ + IO_2^-\\HIO_3 \rightarrow H^+ + IO_3^-\\HIO_4 \rightarrow H^+ + IO_4^-$

In $IO_4^-$, negative charge is distributed over three electronegative atom 'O' which makes it more stable as compared to other two conjugate bases.

Therefore, $HIO_4$ is trongest acid among given.

Group II:

H-Se bond is weaker than H-S bonds which makes it more acidic as breaking of H-Se bond is easier to release H+.

In case of $H_3As$, As is less electronegative than Se. Because of more electronegative nature of Se, electrons of H-Se bond are attracted towards Se and so removal of H+ is easier.

So $H_2Se$ is the strongest acid among give.

Group III:

Acidity is also affected by bond distance and electronegativity of the central element.

Here, electronegativity dominates over bond distance.

Cl has the highest electronegativity among given. Because of hugh electronegativity, electrons are attracted towards Cl, and release of H+ becomes easier as compared to other two.

So, $HClO_2$ is the strongest acid among given.