Question

Regarding the hydrides of group 15 elements \(EH_3\) \((E = N, P, As, Sb)\), select the correct statement(s):
[A.] The stability of hydrides decreases down the group.
[B.] The basicity of hydrides decreases down the group.
[C.] The reducing character increases down the group.
[D.] The boiling point increases down the group. Choose the correct answer:

• A. A, B, C & D
• B. A, B & C only
• C. B & C only
• D. A & D only

Hint:

Trends in group hydrides are governed by bond strength, atomic size, and intermolecular forces.

Answer 1

The Correct Option is A

Concept: Down group 15, atomic size increases and E–H bond strength decreases, influencing stability, basicity, reducing nature, and boiling point.
Step 1: Stability of hydrides \[ \text{NH}_3>\text{PH}_3>\text{AsH}_3>\text{SbH}_3 \] Due to decreasing E–H bond strength down the group. \(\Rightarrow\) Statement A is true.
Step 2: Basicity of hydrides Basicity depends on availability of the lone pair. As size increases, the lone pair becomes less available. \[ \text{NH}_3>\text{PH}_3>\text{AsH}_3>\text{SbH}_3 \] \(\Rightarrow\) Statement B is true.
Step 3: Reducing character Reducing character increases as E–H bond weakens down the group. \[ \text{NH}_3<\text{PH}_3<\text{AsH}_3<\text{SbH}_3 \] \(\Rightarrow\) Statement C is true.
Step 4: Boiling point Although \(\text{NH}_3\) shows hydrogen bonding anomaly, overall boiling point increases down the group due to increased molar mass. \(\Rightarrow\) Statement D is true. Final Conclusion: \[ \boxed{\text{A, B, C and D are all correct}} \]