Question

Identify the incorrect statement related to ${PCl_5}$ from the following:

• A. Axial P �Cl bonds are longer than equatorial P�Cl bonds
• B. ${PCl_5}$ molecule is non-reactive
• C. Three equatorial P - Cl bonds make an angle of 120� with each other
• D. Two axial P - Cl bonds make an angle of 180� with each other

Answer 1

The Correct Option is B

To determine the incorrect statement about ${PCl_5}$, let's analyze each of the given statements in the context of chemistry knowledge about phosphorus pentachloride.

1. Axial P – Cl bonds are longer than equatorial P – Cl bonds: ${PCl_5}$ has a trigonal bipyramidal geometry. In this structure, the three equatorial chlorine atoms are at 120° to each other and are bonded more strongly compared to the two axial chlorine atoms, which are bent away from the plane. This causes the axial bonds to be longer than equatorial bonds due to bond angle strain. Therefore, this statement is correct.
2. The ${PCl_5}$ molecule is non-reactive: ${PCl_5}$ is actually quite reactive. It readily hydrolyzes in water to form phosphoric acid and hydrochloric acid. Thus, this statement is incorrect and is the correct answer to the question.
3. Three equatorial P - Cl bonds make an angle of 120° with each other: This is characteristic of the trigonal bipyramidal structure where the three equatorial bonds are at 120° to each other. Hence, this statement is correct.
4. Two axial P - Cl bonds make an angle of 180° with each other: The axial bonds in the trigonal bipyramidal structure are aligned opposite to each other, creating a 180° angle. Therefore, this statement is correct.

Since the statement "${PCl_5}$ molecule is non-reactive" is incorrect, it is the answer to the question.