Question

The strongest reducing agent among the following is:

• A. SbH$_3$
• B. NH$_3$
• C. BiH$_3$
• D. PH$_3$

Hint:

In a group, reducing character increases down the group due to an increase in atomic size and a decrease in bond strength.

Answer 1

The Correct Option is C

Step 1: Understanding Reducing Agent Strength 
A reducing agent donates electrons and gets oxidized. - The strength of a reducing agent increases as we move down the group in the periodic table. - This happens because the atomic size increases, and the bond strength between the central atom and hydrogen weakens, making electron donation easier. 
Step 2: Trend in Group 15 Hydrides 
- Group 15 hydrides: \( NH_3, PH_3, AsH_3, SbH_3, BiH_3 \). - The reducing character increases as: \[ NH_3<PH_3<AsH_3<SbH_3<BiH_3 \] - Thus, BiH$_3$ is the strongest reducing agent among the given choices.