Question

Which of the following compounds is most acidic?

• A. $H_{2}O$
• B. $H_{2}S$
• C. $H_{2}Se$
• D. $H_{2}Te$

Answer 1

The correct option is D $H_{2}Te$

In binary acids such as $H_{2}S$ and $H_{2}Se$, the H–Se bonds is longer than the H–S bonds as Se is larger than S. The H–Se bond is therefore weaker than the H–S bond and $H_{2}Se$ is thus a stronger acid than $H_{2}S$.

The order is therefore $H_{2}O$ < $H_{2}S$< $H_{2}Se$ < $H_{2}Te$