Question

$\textbf{Choose the correct statements about the hydrides of group 15 elements.}$
A. The stability of the hydrides decreases in the order $\text{NH}_3 > \text{PH}_3 > \text{AsH}_3 > \text{SbH}_3 > \text{BiH}_3$
B. The reducing ability of the hydrides increases in the order $\text{NH}_3 < \text{PH}_3 < \text{AsH}_3 < \text{SbH}_3 < \text{BiH}_3$
C. Among the hydrides, $\text{NH}_3$ is a strong reducing agent while $\text{BiH}_3$ is a mild reducing agent.
D. The basicity of the hydrides increases in the order $\text{NH}_3 < \text{PH}_3 < \text{AsH}_3 < \text{SbH}_3 < \text{BiH}_3$
Choose the most appropriate from the option given below:

• A. A and B only
• B. C and D only
• C. B and C only
• D. A and D only

Answer 1

Answer: (C)

B and C only

Answer 2

Analysis of Statement A: The stability of hydrides does indeed decrease as we go down the group due to increasing atomic size and decreasing bond strength. Thus, the order is NH3 > PH3 > AsH3 > SbH3 > BiH3 is correct.

Analysis of Statement B: The reducing ability of the hydrides increases down the group due to the increase in bond length and decrease in bond dissociation energy, making NH3 < PH3 < AsH3 < SbH3 < BiH3 correct.

Analysis of Statement C: NH3 does exhibit some reducing properties but is generally considered a weak reducing agent. On the other hand, BiH3 can act as a mild reducing agent. Therefore, the statement is correct.

Analysis of Statement D: Basicity generally increases down the group, so NH3 < PH3 < AsH3 < SbH3 < BiH3 is true.

Conclusion: Statements A and D are true, while statements B and C are indeed correct. Therefore, the best answer that reflects this is: B and C only