Question

Which of the following compounds is most acidic in nature?

• A. \(\text{H}_2\text{O}\)
• B. \(\text{H}_2\text{S}\)
• C. \(\text{H}_2\text{Se}\)
• D. \(\text{H}_2\text{Te}\)

Hint:

Acidity of group 16 hydrides rises down the group because the H-E bond gets weaker as E gets larger.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The acid strength of a hydride \(\text{H}_2\text{E}\) depends on how easily it gives up \(\text{H}^+\). A weaker H-E bond means an easier release of \(\text{H}^+\) and a stronger acid.

Step 2: Trend in bond strength:
Going down group 16 (O, S, Se, Te), the size of the atom E increases. The overlap between the H 1s orbital and the orbital of E gets poorer, so the H-E bond becomes longer and weaker.

Step 3: Compare the hydrides:
The H-E bond enthalpy decreases in the order \(\text{H}_2\text{O} > \text{H}_2\text{S} > \text{H}_2\text{Se} > \text{H}_2\text{Te}\). So acidity increases in the order \(\text{H}_2\text{O} < \text{H}_2\text{S} < \text{H}_2\text{Se} < \text{H}_2\text{Te}\).

Step 4: Why the other options are wrong.
Water has the strongest O-H bond and is the weakest acid. \(\text{H}_2\text{S}\) and \(\text{H}_2\text{Se}\) are more acidic than water but less than \(\text{H}_2\text{Te}\), which has the longest and weakest bond.

Final Answer:
The most acidic hydride is \(\text{H}_2\text{Te}\). \[ \boxed{\text{(D) }\text{H}_2\text{Te}} \]