Question

Given below are two statements: 
Statement I: $ H_2Se $ is more acidic than $ H_2Te $ 
Statement II: $ H_2Se $ has higher bond enthalpy for dissociation than $ H_2Te $
In the light of the above statements, choose the correct answer from the options given below.

• A. Statement I is false but Statement II is true
• B. Statement I is true but Statement II is false
• C. Both Statement I and Statement II are false
• D. Both Statement I and Statement II are true

Hint:

- Remember the periodic trend: acidity of hydrides increases down the group - Bond enthalpy decreases with increasing atomic size in a group - Larger atoms form weaker bonds, making their hydrides more acidic

Answer 1

The Correct Option is A

To answer the question, we first need to analyze each statement separately in the context of chemistry, specifically the properties of hydrides within the chalcogen group.

1. Statement I: \( H_2Se \) is more acidic than \( H_2Te \)

The acidity of hydrides in the group 16 elements (chalcogen group) increases as we move down the group. Therefore, the correct trend in acidity for \( H_2\text{X} \) hydrides (where \( \text{X} \) is a chalcogen) is: \( H_2O < H_2S < H_2Se < H_2Te \). Hence, \( H_2Te \) is more acidic than \( H_2Se \) due to an increase in atomic size and decrease in bond strength, which facilitates the release of protons.

Therefore, Statement I is false.

1. Statement II: \( H_2Se \) has a higher bond enthalpy for dissociation than \( H_2Te \)

Bond enthalpy typically decreases as we move down the group due to the increasing size of the atoms, which results in weaker bonds. Therefore, \( H_2Se \), which is higher in the group than \( H_2Te \), will indeed have a higher bond enthalpy (i.e., stronger bonds) than \( H_2Te \).

Thus, Statement II is true.

Considering the above analysis, the correct option is that Statement I is false but Statement II is true.

Answer 2

Analysis of Statement I:
- Acidic character increases down the group for hydrides (H₂O < H₂S < H₂Se < H₂Te) - H₂Te is more acidic than H₂Se because:

• Te is larger than Se, making Te-H bond weaker
• H⁺ ion is more easily released from H₂Te

- Therefore, Statement I is false

Analysis of Statement II:
- Bond enthalpy decreases down the group (H-Se > H-Te)
- H₂Se has higher bond dissociation enthalpy because: 

• Se is smaller than Te, forming stronger bonds
• Bond strength decreases with increasing atomic size

- Therefore, Statement II is true