NEETChemistryp Block Elements (Group 15, 16, 17 & 18)
Which of the following correctly represents the order of acidic strength of Group 16 hydrides and the primary reason for this trend?
Options
- AH₂O > H₂S > H₂Se > H₂Te ; Reason: Decrease in electronegativity of the central atom down the group.
- BH₂O < H₂S < H₂Se < H₂Te ; Reason: Increase in electronegativity of the central atom down the group.
- CH₂O > H₂S > H₂Se > H₂Te ; Reason: Presence of strong intermolecular hydrogen bonding in H₂O .
- DH₂O < H₂S < H₂Se < H₂Te ; Reason: Decrease in H-E bond dissociation enthalpy down the group.
Correct answer
D. H₂O < H₂S < H₂Se < H₂Te ; Reason: Decrease in H-E bond dissociation enthalpy down the group.
Step-by-step solution
Down Group 16, as the atomic size of the central atom (E) increases, the H-E bond length increases. This leads to a decrease in the H-E bond dissociation enthalpy down the group. Because the bond becomes weaker and easier to break, the release of H^+ ions becomes progressively easier. Therefore, the acidic strength increases in the order H₂O Answer: H₂O < H₂S < H₂Se < H₂Te ; Reason: Decrease in H-E bond dissociation enthalpy down the group.