What is the order of reducing character for $AsH_3, NH_3, PH_3$ (group $15$ hydrides)?

Question

Consider the following statements:
Statement-I: H$_2$Se is more acidic than H$_2$Te.
Statement-II: H$_2$Se has higher bond dissociation enthalpy than H$_2$Te.
In light of the above statements, choose the correct option:

Answer 1

The question pertains to the reducing nature of hydrides of group 15 elements, particularly $NH_3, PH_3$, and $AsH_3$. To determine the order of their reducing character, we need to understand the factors influencing this property.

Reducing character in hydrides generally increases as we move down the group in the periodic table. This is because:

The central atom increases in size, which leads to an increase in the H-M-H bond angle, making it easier for the hydride to lose hydrogen and act as a reducing agent.
The bond strength between the central atom and hydrogen decreases as we move down the group. Weaker M-H bonds are more easily broken, increasing the reducing nature.

Let's apply this knowledge to the hydrides in question:

NH_3: Nitrogen is at the top of group 15, resulting in a smaller size and stronger N-H bond. It is less reducing compared to the heavier analogs.
PH_3: Phosphorus is below nitrogen, so the bond is weaker compared to N-H, thus PH_3 is more reducing than NH_3.
AsH_3: Arsenic lies below phosphorus, implying even weaker bonds than P-H, leading to AsH_3 having the strongest reducing ability among the three.

Considering these factors, the reducing character increases as we move from NH_3 to AsH_3. Hence, the correct order is:

AsH_3 > PH_3 > NH_3

This explains why the correct answer is AsH_3 > PH_3 > NH_3, as the reducing character increases down the group.

Answer 2

The question pertains to the reducing nature of hydrides of group 15 elements, particularly $NH_3, PH_3$, and $AsH_3$. To determine the order of their reducing character, we need to understand the factors influencing this property.

Reducing character in hydrides generally increases as we move down the group in the periodic table. This is because:

The central atom increases in size, which leads to an increase in the H-M-H bond angle, making it easier for the hydride to lose hydrogen and act as a reducing agent.
The bond strength between the central atom and hydrogen decreases as we move down the group. Weaker M-H bonds are more easily broken, increasing the reducing nature.

Let's apply this knowledge to the hydrides in question:

NH_3: Nitrogen is at the top of group 15, resulting in a smaller size and stronger N-H bond. It is less reducing compared to the heavier analogs.
PH_3: Phosphorus is below nitrogen, so the bond is weaker compared to N-H, thus PH_3 is more reducing than NH_3.
AsH_3: Arsenic lies below phosphorus, implying even weaker bonds than P-H, leading to AsH_3 having the strongest reducing ability among the three.

Considering these factors, the reducing character increases as we move from NH_3 to AsH_3. Hence, the correct order is:

AsH_3 > PH_3 > NH_3

This explains why the correct answer is AsH_3 > PH_3 > NH_3, as the reducing character increases down the group.

What is the order of reducing character for \(AsH_3, NH_3, PH_3\) (group \(15\) hydrides)?

The Correct Option is C

Solution and Explanation

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